The science of groundwater, its origin, conditions of occurrence, laws of movement, physical and chemical properties, connections with atmospheric and surface waters are called hydrogeology.

For builders, groundwater in some cases serves as a source of water supply, and in others it acts as a factor complicating construction. It is especially difficult to carry out excavation and mining work in conditions of an influx of groundwater that floods pits, quarries, trenches, underground mine workings: mines, adits, tunnels, galleries, etc. Groundwater worsens the mechanical properties of loose and clayey rocks, can act as an aggressive environment in relation to building materials, cause the dissolution of many rock pores (gypsum, limestone, etc.) with the formation of voids, etc.

Builders must study groundwater and use it for production purposes, and be able to resist its negative impact during the construction and operation of buildings.

Water properties of rocks

Rocks in relation to water are characterized by the following indicators: moisture capacity, water yield and water permeability. Indicators of these properties are used in various hydrogeological calculations.

Moisture capacity - the ability of a rock to contain and retain water. In the case when all the pores are filled with water, the rock will be in a state of complete saturation. Humidity corresponding to this state is called total moisture capacity W n. B:

wfi.b = L/Rec,

Where P - porosity; rsk is the density of the rock skeleton.

Highest value W a B coincides with the rock porosity value. According to the degree of moisture holding capacity, rocks are divided into very moisture-intensive(peat, loam, clay), low-moisture resistant(marl, chalk, loose sandstones, fine sands, loess) and non-moisture-intensive, do not retain water (pebbles, gravel, sand).

Water yieldW e - the ability of rocks saturated with water to release gravitational water in the form of free flow. In this case, it is believed that physically bound water does not flow out of the pores of the rock, so they accept W z = W n .„ - W MMB .

The amount of water loss can be expressed as a percentage of the volume of water freely flowing from the rock to the volume of the rock or the amount of water flowing out of 1 m 3 of rock (specific water yield). Coarse-grained rocks, as well as sands and sandy loams, in which the value of W B ranges from 25 to 43%. Under the influence of gravity, these rocks are capable of releasing almost all the iodine present in their pores. In clays, water loss is close to zero.

Water permeability - the ability of rocks to pass gravitational water through pores (loose rocks) and cracks (dense rocks). The larger the pore size or the larger the cracks, the higher the water permeability of the rocks. Not every rock that is inherently porous is capable of allowing water to pass through, for example, ff clay: with a porosity of 50-60% it practically does not allow water to pass through.

The water permeability of rocks (or their filtration properties) is characterized by filtration coefficientk$ (cm/s, m/h or m/day), which is the speed of movement of underground water with a hydraulic gradient equal to 1.

By size kf rocks are divided into three groups: 1) water-permeable - &f > 1 m/day (pebbles, gravel, sand, fractured rocks); 2) semi-permeable - k li > = 1...0.001 m/day (clayey sands, loess, peat, loose varieties of sandstones, less often porous limestones, marls); 3) impenetrable - & f< 0,001 м/сут (мас­сивные породы, глины). Непроницаемые породы принято назы­вать aquicludes, and semi-permeable and water-permeable - by the single term water-permeable, or aquifers, horizons

§ 3. Chemical composition of groundwater.

Water as an aggressive natural environment to building structures

All groundwater contains a certain amount of salts, gases, and organic compounds in a dissolved state.

Gases dissolved in water (O, CO 2, CH4, H2S, etc.) determine the degree of suitability of water for drinking and technical purposes. The amount of dissolved salts should not exceed 1 g/l. The content of chemical elements harmful to human health (uranium, arsenic, etc.) and pathogenic bacteria is not allowed.

Chlorides, sulfates and carbonates are most common in groundwater. Groundwater is divided into fresh(up to 1 g/l dissolved salts), brackish(from 1 to 10 g/l), salty(10-35 g/l) and pickles(more than 35 g/l). The amount and composition of salts is determined by chemical analysis in milligrams per liter (mg/l) or millimoles per liter (mmol/l).

The presence of salts gives water properties such as hardness and aggressiveness.

Rigidity groundwater is determined by the amount of Ca 2+ and Mg 2+ ions dissolved in water and is expressed in millimoles per liter. Distinguish

1. general hardness caused by the content of all calcium and magnesium salts in water: Ca(HCO 3) 2; Mg(HCO 3) 2, CaSO4, MgSO 4, CaCl 2, MgCI 2;

2. carbonate, or temporary, due to the content of calcium and magnesium bicarbonates, removed by boiling (precipitate in the form of carbonates);

3. non-carbonate, or permanent remaining in the water after the removal of bicarbonates. Based on total hardness, natural waters are divided into 5 groups:

Water rating Hardness, mmol/l

Very soft up to 1.5

Soft 1.5-3.0

Moderately soft 3-6

Hard 6-9

Very hard above 9

Hard water forms scale in boilers, soap suds are difficult to form in them, etc.

Aggressiveness groundwater is expressed in the destructive effect of salts dissolved in water on building materials, in particular on Portland cement. In existing standards that assess the degree of aggressiveness of water in relation to concrete, in addition to the chemical composition of water, the filtration coefficient of rocks is taken into account.

1. Aggressiveness by bicarbonate alkalinity content(leaching aggressiveness) is determined by the value of carbonate hardness. Ground water is aggressive to concrete at a carbonate hardness of 4-2.14 mmol/l (depending on the type of cement in the concrete), and at higher values ​​the water becomes non-aggressive.

2. Aggression according to hydrogen index(general acid aggressiveness) is assessed by pH value. In formations with high water permeability it is aggressive at pH = 6.7-7.0, and in low permeability formations - at pH = 5

3. Aggression by free carbon dioxide content(CO 2) (carbon aggressiveness) is determined by the content of carbon dioxide. There are free, bound and aggressive carbon dioxide.

Agressative carbon dioxide is determined experimentally and by calculation, water is considered aggressive when the carbon dioxide content is >15 mmol/l in highly permeable soils and >55 mmol/l for weakly permeable soils.

4. Aggression by content of magnesium salts determined by the content of Mg 2+ ion. In poorly filtering soils, water is aggressive with a magnesium content of >2000 mg/l, and in other soils > 1000 mg/l.

5. Aggression by caustic alkali content is estimated by the number of K + and Na + ions. Water is aggressive to concrete when the content of these ions is >80 g/l in highly permeable and >50 g/l in poorly permeable soils.

6. Sulfate aggressiveness. This type of aggressiveness is determined by the content of SO 4 2- ions. In highly permeable soils, it depends on the content of the C1 - ion. When the content of sulfate ions is less than 250-300 mg/l in all soils, water is non-aggressive, in all other cases it is aggressive, even towards special cements.

Aggressiveness in the content of chlorides, sulfates, nitrates and other salts and caustic alkalis is usually associated with artificial sources of groundwater pollution with a total content of (aggressive ions >10 g/l.

The aggressiveness of groundwater is determined by comparing data from chemical analyzes of water with the requirements of SNiP 2.02.11-85. To combat it, special cements are used, waterproofing of underground parts of buildings and structures is carried out, the groundwater level is lowered by installing drainages, etc.

4. Classification and characteristics of types groundwater

Groundwater is classified by hy dravlic sign- non-pressure and pressure, and conditionsoccurrence in the earth's crust - perched water, groundwater, interstratal water (Fig. 50). In addition to these main types, there are a number of groundwaters, such as fissure, karst, mineral, etc.

Verkhovodka.Verkhovodka are temporary accumulations of water in the aeration zone, which are located above the groundwater horizon, where part of the soil pores are occupied by air. Verkhovodka is formed over small aquitards such as lenses of clays and loams in sand, over layers of denser rocks, etc. (Fig. 50), during the infiltration of water during periods of heavy snowmelt and rain. The rest of the time, the perched water evaporates and seeps into the underlying groundwater.

In general, perched water is characterized by: temporary, often seasonal nature, small area of ​​distribution, low power and lack of pressure. Lying within the underground parts of buildings and structures (basements, boiler rooms, etc.), it can cause flooding if drainage or waterproofing measures have not been provided in advance.

During engineering-geological surveys carried out in the dry season, perched water is not always detected. Therefore, its appearance may be unexpected for builders.

Groundwater.Unpaved are called constant in time and significant in area of ​​distribution of groundwater horizons lying on the first aquitard from the surface.

1. Groundwater free-flowing, have a free surface called mirror(or level). The position of the mirror to some extent corresponds to the topography of the area. The depth of the level from the surface varies - from 1 to 50 m or more. The aquifer on which the aquifer lies is called waterproof bed, and the distance from it to

groundwater level - power aquifer (Fig. 51).

2. Nutrition groundwater occurs due to precipitation,

reservoirs and rivers. Food area matches with the area of ​​distribution of groundwater. Groundwater is open to

contamination with various harmful impurities.

3. Groundwater forms flows that are directed towards the slope of the aquitard (Fig. 51).

4. The quantity, quality and depth of groundwater depend

geology of the area and climatic factors.

In construction practice, it is most often encountered

groundwater. They create great difficulties in production

construction work (filling pits, trenches, etc.) and interfering

operate buildings and structures normally.

Interstratal waters called aquifers located between aquitards. They can be non-pressure and pressure, the latter otherwise called artesian.

Interlayer non-pressure waters are relatively rare,

the aquifers are only partially filled with water (Fig. 51).

Pressure(artesian) waters are associated with the occurrence of aquifers

layers inclined to the horizon or in the form of a bend (fold) (Fig. 50

and 52). The area of ​​distribution of confined aquifers is called an artesian basin.

Separate parts of aquifers lie at different altitudes

marks. This creates groundwater pressure. Power area like

as a rule, does not coincide with the area of ​​distribution of interstratal waters.

The pressure of water is characterized by the piezometric level. He can

to be above the surface of the earth or to be below it. In the first case, leaving

through boreholes, water gushes out, in the second it rises

only up to the piezometric level.

Many artesian basins, for example the Don-Donets depression, occupy vast areas, contain a number of aquifers and are an important source of drinking water.

Topic: Hydrogeology as a science. Water in nature.

1. Hydrogeology. Stages of development of hydrogeology.

Let us recall the definition of the science of hydrogeology. Hydrogeology- the science of groundwater, studying its origin, conditions of occurrence and distribution, laws of movement, interaction with water-bearing rocks, formation of chemical composition, etc.

Let us briefly consider the history of the development of this science.

1.1 Stages of development of hydrogeology

In the history of groundwater studies in the USSR, there are 2 periods:

1) pre-revolutionary;

2) post-revolutionary.

In the pre-revolutionary period, three stages in the study of groundwater can be distinguished:

1. accumulation of experience in the use of groundwater (X - XVII centuries)

2. the first scientific generalized information about groundwater (XVII - mid-XIX centuries)

3. establishment of hydrogeology as a science (second half of the 19th century and beginning of the 20th century)

In 1914, the first department of hydrogeology in Russia was organized at the engineering faculty of the Moscow Agricultural Institute (now the Moscow Irrigation Institute).

The post-revolutionary period can be divided into 2 stages:

1. pre-war (1917-1941)

2. post-war

To train hydrogeological engineers, a hydrogeological specialty was established at the Moscow Mining Academy in 1920: a little later it was introduced at other institutes and universities. The most prominent hydrogeologists F.P. began teaching at the institutes. Savarensky, N.F. Pogrebov, A.N. Semikhatov, B.C. Ilyin et al.

By the beginning of the first five-year plan (1928), as well as during subsequent five-year plans, hydrogeological research was carried out in the Donbass, Eastern Transcaucasia, Central Asia, Northern Ukraine, Kazakhstan, Turkmenistan and many other regions of the country.

The First All-Union Hydrogeological Congress, held in 1931, was of great importance for the further development of hydrogeology. in Leningrad.

In the 1930s, summary maps (hydrogeological, mineral water, hydrogeological zoning) were compiled for the first time, which were of great importance for planning further hydrogeological research. At the same time, under the editorship of N.I. Tolstikhin, volumes “Hydrogeology of the USSR” began to be published. Before the Great Patriotic War, 12 issues of this multi-volume work were published.

The post-war stage is characterized by the accumulation of materials in deep-lying waters.

For a more in-depth scientific analysis and broad regional generalization of materials on groundwater, it was decided to prepare for publication 45 volumes of “Hydrogeology of the USSR”, and in addition, compile 5 consolidated volumes.

2. Water in nature. The water cycle in nature.

On the globe, water is found in the atmosphere, on the surface of the earth and in the earth's crust. In the atmosphere water is found in its lower layer - the troposphere - in various states:

1. vapor;

2. droplet liquid;

3. hard.

Superficial water is in liquid and solid state. In the earth's crust water is found in vapor, liquid, solid, and also in the form of hygroscopic and film water. Together, surface and groundwater make up the water shell - hydrosphere.

The underground hydrosphere is limited from above by the surface of the earth; its lower boundary has not been reliably studied.

There are large, internal and small gyres. During a large cycle, moisture evaporates from the surface of the oceans, is transported in the form of water vapor by air currents to land, falls here on the surface in the form of precipitation, and then returns to the seas and oceans by surface and underground runoff.

With a small circulation, moisture evaporates from the surfaces of oceans and seas. It also falls here in the form of precipitation.

The process of the cycle in nature in quantitative terms is characterized water balance, the equation of which the share of a closed river basin has the form for a long-term period:

X = y+Z-W (according to Velikanov),

where x is precipitation per catchment area, mm

y - river flow, mm

Z - evaporation minus condensation, mm

W is the average long-term recharge of deep aquifers due to precipitation or the flow of groundwater to the surface within the river basin.

The internal circulation is provided by that part of the water that evaporates within the continents - from the water surface of rivers and lakes, from land and vegetation, and falls there in the form of precipitation.

3. Types of water in minerals and rocks.

One of the earliest classifications of water types in race rocks was proposed in 1936 by A.F. Lebedev. In subsequent years, a number of other classifications were proposed. Based on Lebedev’s classification, most scientists distinguish the following types of water:

1. Steamy water

Found in the form of water vapor in the air, present in the pores and cracks of rocks and in the soil, it moves along with air currents. Under certain conditions, it can transform into liquid form through condensation.

Vaporous water is the only type that can move in pores with little moisture.

2. Bound water

Present mainly in clayey rocks, it is held on the surface of particles by forces significantly exceeding the force of gravity.

A distinction is made between tightly bound and loosely bound water.

A) strongly bound water(hydroscopic) it is in the form of molecules in an absorbed state, held on the surface of particles by molecular and electrostatic forces. It has high density, viscosity and elasticity, is characteristic of finely dispersed rocks, is not capable of dissolving salts, and is not accessible to plants.

b) loosely knit(film) is located above tightly bound water, is held by molecular forces, is more mobile, the density is close to the density of free water, is able to move from particles to particles under the influence of sorption forces, the ability to dissolve salts is reduced.

3. Capillary water

It is located in the capillary pores of rocks, where it is held and moved under the influence of capillary (meniscus) forces acting at the boundary of water and air located in the pores. It is divided into 3 types:

A) actual capillary water is located in the pores in the form of moisture from the capillary floodplain above the groundwater level. The thickness of the capillary floodplain depends on the granulometric composition. It varies from zero in pebbles to 4-5 m in clayey rocks. Capillary water itself is available to plants.

b) suspended capillary water is located predominantly in the upper horizon of the rock or in the soil and is not in direct connection with the groundwater level. When the moisture content of the rock increases above the minimum moisture capacity, water flows into the underlying layers. This water is available to plants.

V) pore corner water is held by capillary forces in the pores of sand and clay rocks at the points of contact of their particles. This water is not used by plants; when humidity increases, it can turn into suspended water or into capillary water itself.

4. Gravity water

Submits to gravity. The movement of water occurs under the influence of this force and transmits hydrostatic pressure. It is divided into 2 types:

A) seeping- free gravitational water in a state of downward movement in the form of separate streams in the aeration zone. The movement of water occurs under the influence of gravity.

b) aquifer moisture, which saturates the aquifers to PV. Moisture is retained due to the waterproofness of the waterproof layer (further discussion refers to the topic “Gravitational water”).

5. Water of crystallization

It is part of the crystal lattice of a mineral, such as gypsum (CaS0 4 2H 2 O), and retains its molecular shape.

6. Solid water in the form of ice

In addition to the above six species, there are chemically bound water, which participates in the structure of the crystal lattice of minerals in the form of H +, OH ions,” i.e., does not retain its molecular form.

4. The concept of porosity and porosity.

One of the most important hydrogeological indicators of rocks is their porosity. In sandy rocks there are steam porosity, and in strong ones - cracked.

Groundwater fills pores and cracks in rocks. The volume of all voids in rock is called duty cycle. Naturally, the greater the porosity, the more water the rock can hold.

The size of voids is of great importance for the movement of groundwater in rocks. In small pores and cracks, the area of ​​contact of water with the walls of the voids is greater. These walls provide significant resistance to the movement of water, so its movement in fine sand, even with significant pressure, is difficult.

The porosity of rocks is distinguished: capillary(porosity) and non-capillary.

To capillary duty cycle include small voids where water moves mainly under the influence of surface tension and electrical forces.

To non-capillary duty cycle include large voids devoid of capillary properties, in which water moves only under the influence of gravity and pressure difference.

Small voids in rocks are called porosity.

There are 3 types of porosity:

2. open

3. dynamic

Total porosity is quantitatively determined by the ratio of the volume of all small voids (including those not communicating with each other) to the entire volume of the sample. Expressed in fractions of a unit or as a percentage.

Or

where V n is the volume of pores in the rock sample

V – sample volume

Total porosity is characterized by the porosity coefficient e.

Porosity coefficient e is expressed by the ratio of the volume of all pores in the rock to the volume of the solid part of the rock (skeleton) V c, expressed in fractions of unity.

This coefficient is widely used especially in research

clay soils. This is due to the fact that clay soils swell when moistened. Therefore, it is preferable to express clay porosity through e.

The porosity ratio can be expressed as follows

, dividing the numerator and denominator by V c we get

The value of total porosity is always less than 1 (100%), and the value e may be equal to 1 or greater than 1. For plastic clays e ranges from 0.4 to 16.

Porosity depends on the nature of the composition of particles (grains).

Non-capillary porosity includes large pores in coarse clastic rocks, cracks, channels, caves and other large voids. Cracks and pores can communicate with each other or be torn.

Open porosity characterized by the ratio of the volume of interconnected open pores to the entire volume of the sample.

For granular, unconsolidated rocks, the open porosity is close in value to the total.

Dynamic porosity is expressed as the ratio to the entire sample volume of only that part of the pore volume through which liquid (water) can move.

Studies have shown that water does not move throughout the entire volume of open pores. Part of the open pores (especially at the junction of particles) is often occupied by a thin film of water, which is firmly held by capillary and molecular forces and does not participate in movement.

Dynamic porosity, unlike open porosity, does not take into account the volume of pores occupied by capillary-bound water. Typically, dynamic porosity is less than open porosity.

Thus, the fundamental difference between the characterized types of porosity lies (quantitatively) in the fact that in cemented rocks the total porosity is more open, and the open porosity is more dynamic.

Control questions:

1. What does the science of hydrogeology study?

2. How does the water cycle work in nature?

3. Name the types of water found in minerals and rocks.

4. What is porosity? What are its types? How is porosity determined?

5. What do I mean by duty cycle? Name and describe its types.

Hydrogeology is the science of groundwater. Underground waters are those located below the surface of the earth, confined to various rocks and filling pores, cracks and karst voids. Hydrogeology studies the origin and development of groundwater, the conditions of its occurrence and distribution, the laws of movement, the processes of interaction of groundwater with the host rocks, the physical and chemical properties of groundwater, its gas composition; is engaged in studying the practical use of groundwater for drinking and domestic water supply, as well as developing measures to combat groundwater during the construction and operation of various facilities, mining, etc.

Groundwater is in a complex relationship with the rocks that make up the earth's crust, the study of which is the subject of geology; therefore, geology and hydrogeology are inextricably linked, as evidenced by the very name of the science in question.

Hydrogeology covers a significant range of issues studied by other sciences and is in close connection with meteorology, climatology, hydrology, geomorphology, soil science, lithology, tectonics, geochemistry, chemistry, physics, hydraulics, hydrodynamics, hydraulic engineering, mining, etc.

The importance of groundwater in geological processes is extremely great. Under the influence of groundwater, the composition and structure of rocks change (physical and chemical weathering), destruction of slopes occurs (landslides), etc.

Hydrogeology is a complex science and is divided into the following independent sections:

1. “General hydrogeology” - studies the water cycle in nature, the origin of groundwater, the physical properties and chemical composition of water as complex dynamic natural systems and their classification.

2. “Dynamics of groundwater” - studies the patterns of movement of groundwater, which make it possible to solve issues of water supply, irrigation, drainage, when determining water inflows into mine workings and many others.

3. “Regional hydrogeology” - studies the patterns of distribution of groundwater in the territory and, accordingly, the generality of hydrogeological conditions of certain territories, produces zoning of the latter.

4. “Hydrogeochemistry” - studies the formation of the chemical composition of groundwater.

5. “Mineral waters” - studies the patterns of origin and formation of medicinal waters and waters of industrial importance (for extracting salt, iodine, bromine and other substances from them), the distribution of these waters and the best ways to exploit them.

Lecture 1. Hydrosphere

Plan:

Hydrosphere and water cycle in nature

Types of water in rocks

Properties of rocks in relation to water

The concept of aeration and saturation zone

I. Hydrosphere and water cycle in nature.Water on the globe is in a constant cycle. There are large and small gyres. The process of the natural cycle is characterized in quantitative terms by water balance (Fig. 1). The level of which according to B.I. Kudelin expresses

x=y+z±w

x – precipitation, mm

y – river runoff, mm

z – evaporation, mm

w – average long-term recharge of deep horizons, mm

Part of the atmospheric precipitation that penetrates the rocks reaches the surface of the aquifers and goes to feed them. Surface and underground flow together form the total river flow. Underground runoff and total evaporation constitute the moistening of the gross territory, equal to the difference between precipitation and surface runoff. From 5-7 to 15-20% of precipitation is used for food in the territory of the Republic of Belarus. Underground nutrition (infiltration) depends on the climatic conditions of the territory, soil and vegetation layer, geomorphological and geological factors.

II. Types of water in rocks.The following types of water in rocks are distinguished: vaporous, hygroscopic, film, gravitational, crystallization, chemically bound.

Rice. 1. Water balance diagram

Vaporous – is found in the form of water vapor in the air, present in the pores and cracks of mountain towns. When cooled by condensation it turns into liquid water.

Hygroscopic(strongly bound) water is held on the surface of particles by molecular and electrostatic forces. It does not transmit hydrostatic pressure, does not have dissolving ability, and does not freeze up to 78ºC. When heated to 100-105ºС it is completely removed. Contained in sands 1%, sandy loams 8%, clays up to 18%, inaccessible to plants.

Film (loosely bound) water is formed by condensation of water vapor. It covers the surface of particles with a thin film of 0.01 mm, is held by molecular forces, the density is close to the density of free water, is able to move from particle to particle under the influence of sorption forces, and does not transmit hydrostatic pressure. The content in sands is 1-7%, sandy loams 9-13%, loams 15-23%, clays 25-45%. The content of this water dramatically changes the strength properties of clayey rocks.

Capillary water (self-capillary, suspended capillary water) is contained in thin pores in the form of a capillary fringe above the groundwater level in the humidity range from the lowest humidity (LH) to total humidity (TH). The height of the capillary rise is for pebbles, gravel, coarse-grained sands-0, medium-grained sands 15-35 cm, fine-grained sands - 35-100 cm, sandy loams - 100-150, clays - 400-500 cm.

Gravitational water is subject to gravity. The movement occurs under the influence of gravity and pressure gradient, transmitting hydrostatic pressure. In general, hydrogeology studies these waters.

Crystallizationwater is part of the crystal lattice of minerals (CaSO 4 2H 2 O).

Chemically boundwater (constitutional) participates in the structure of the crystal lattice of minerals.

III. The main properties of rocksare: density, bulk density, porosity, water permeability, moisture capacity, solubility, water loss. They depend on the mineral composition of the rocks, their structure, composition, fracturing, and porosity.

Grading– percentage content of particles of various sizes in loose rock. The granulometric composition of non-cohesive rocks according to GOST 12536-67 is determined using sieve analysis, which consists of sequentially sifting the rock through a set of sieves and weighing the material remaining on each sieve. For sifting sandy rocks, a set of sieves with hole diameters of 10, 5, 2, 1, 0.5, 0.25, 0.1 mm is used. For clarity, the granulometric composition of rocks is presented in the form of a granulometric composition curve plotted on a semi-logarithmic scale (Fig. 2).

Rice. 2. Particle size distribution chart

The heterogeneity curve allows you to calculate the value of the heterogeneity coefficient: where is the heterogeneity coefficient, are the diameters of particles, less than which a given rock contains 60 and 10% of particles by weight, respectively.

The particle size distribution of associated rocks is determined by the hydrometric method or the pipette method, based on the different settling rates of particles in water.

Density (γ-gamma) – the ratio of the mass of solid particles to their volume. The density of sand-clay particles lies in the range (g/cm 3 ) from 2.5 to 2.8 g/cm³, sandy loam 2.70, loam – 2.71, clay – 2.74.

Volumetric mass wet rock (γ O ) is the mass per unit volume of rock at natural moisture and porosity:

Where P is sample mass, g; V – sample volume, cm³,

γ o – varies from 1.3-2.4, g/cm³.

A more constant value is the volumetric mass of the rock skeleton - the mass of the solid component per unit volume of the rock. Calculated

Where w is rock moisture content, %

Porosity – the total volume of all pores in a unit volume of rock. Porosity is defined as the ratio of the volume of pores in the rock (Vp) to the total volume occupied by the rock (V), expressed as a percentage; p= Vp/ V·100%. In addition, the porosity coefficient ε (epsilon) = n/(1-n) is often used. The porosity of clayey rocks reaches 50-60%, sands - 35-40%, sandstones - 2-38%, limestones, marls - 1.5-22%, granites, gneisses, quartzites 0.02-2%.

Absolute humidity– the ratio of the mass of water to the mass of absolutely dry soil in a given volume, expressed as a percentage.

Natural humidity– the amount of water contained in the pores of rocks under natural conditions. Humidity expressed in relation to the volume of rock is called relative humidity.

Moisture capacity – maximum molecular characterizes the amount of water retained in the rock due to molecular adhesion forces between soil particles and water (shows the content of bound water). There are total, capillary and minimum moisture capacity.

Water permeability– the ability of rocks to pass water through themselves, the movement of water in soils under pressure is called filtration. Solubility - the ability of rocks to dissolve in water, depends on temperature, water flow speed, CO content 2 etc.

IV. The concept of the saturation zone.In loose rocks below the groundwater level, all the pores are filled with water - the saturation zone, the layer above is called the aeration zone - its thickness is equal to the depth of the groundwater.

aquifer– rock layers that are homogeneous in lithological composition and hydrogeological properties.

Aquifer complex– a complex of water-saturated rocks confined to a strata of a certain age.

Lecture 2. Origin and dynamics of groundwater

Plan:

Origin of groundwater

Groundwater filtration laws

Determination of the direction and speed of groundwater movement

Basic hydrogeological parameters.

I. By origin, groundwater is divided into:

Infiltration– water is formed as a result of seepage of precipitation from the surface of the earth, surface water into pores and cracks in rocks. This is the main group of infiltration waters contained in the earth's crust

Condensation– water is formed by the condensation of water vapor in the aeration zone, caves, etc.

Sedimentation– are formed due to the waters of reservoirs in which sedimentary rocks accumulated.

Igneous origin -are formed during volcanic eruptions.

II. Filtration – movement of groundwater in the pores and cracks of rocks. If the movement of water occurs in rocks that are not completely saturated with water, then it is called infiltration (through the aeration zone). The flow of sediment or surface water through cracks in rocks is called inflation. There are laminar and turbulent water movements.

The basic law of laminar fluid movement in porous rocks was established by Darsú (1856). Based on this law, Dupuú (1857) developed a relationship for determining the flow rate of groundwater and its influx to water intakes.

N.E. made a great contribution to the study of groundwater dynamics. Zhukovsky, N.N. Pavlovsky, P.Ya. Polubarinova-Kochina, G.N. Kamensky, S.N. Numerov, M.E. Altovsky, V.M. Shestakov, N.N. Verigin, A.I. Silin-Bekchurin, A.N. Myatiev, S.F. Averyanov and others.

Laminar (parallel jet) movement occurs without speed pulsation. The steady movement of groundwater is characterized by constancy over time in any section of power, pressure gradient of filtration rate and flow rate. Unsteady movement of groundwater is a movement in which the flow rate, direction and slope of the flow changes over time.

Turbulent movement (vortex) is characterized by a pulsation of speed, as a result of which different layers of the flow are mixed (karst waters, along cracks).

Laws of groundwater filtration. Linear filtration law.

Laminar movement of groundwaterobeys the linear law of filtration (Darcy's law - after the name of the French scientist who established this law in 1856 for porous granular rocks). This law is formulated as follows: the filtration rate during laminar flow is proportional to the hydraulic slope to the first power.

V=KI, where,

V – filtration speed;

K – filtration coefficient;

I – pressure gradient hydraulic slope;

I=(H 1 -H 2 )/e

If e=1, then V=K, i.e., with pressure gradient =1, the filtration coefficient is equal to the filtration rate.

Q=KIω, where

Q – filtration flow rate – the amount of water flowing through a given cross-section of the flow per unit time, m³/day, K – filtration coefficient, I – pressure gradient, ω – cross-section.

Q – determined by measuring vessels. Q=V/t, l/s.

Determination of the flow rate of sources using weirs.

Water consumption of trapezoidal section:

Q=0.0186bh√h, l/sec, where

Q – source flow, l/sec;

b – width of the lower weir rib in cm;

h – height of the water level in front of the spillway rib, cm.

Triangular section:

Q=0.014h 2 √h, l/s.

Rectangular section:

Q=0.018bh√h, l/s.

A weir with a trapezoidal cross-section is used to measure large flow rates - more than 10 l/sec (100-200 l/sec), and less than 10 l/sec - with a triangular or rectangular cross-section.

Pressure gradient can be determined by hydroisohypses - lines connecting identical marks of the groundwater surface or hydroisopiesis - lines connecting points of equal pressure of pressurized water. The pressure gradient is not constant over time; it can increase when groundwater recharge increases and decrease when it weakens.

The movement of groundwater does not occur through all sections of the flow, but only through a part of it corresponding to the area of ​​pores or cracks. The actual speed of filtered water is:

V=Q/nω, where:

Q – filtration flow rate, m³/day;

n – rock porosity;

ω – flow cross section, m 2 .

In clayey rocks, n – constitutes active porosity, which characterizes the part of the rock cross-section capable of passing gravitational water.

According to G.N. Kamensky's linear filtration law is valid at groundwater movement speeds of up to 400 m/day.

Filtration through clayey rocks can begin only if the pressure gradient exceeds the initial pressure gradient. For clays and loams this initial gradient is different.

Nonlinear filtration law (Chezy-Krasnopolsky law)characterizes turbulent movement, characteristic of highly fractured rocks with large voids: , V – filtration rate m/day. K – filtration coefficient, m/day, I – pressure gradient.

III. Determination of the direction and speed of movement of groundwater.The movement of groundwater in the pores of loose rocks cannot be considered as the movement of a stream, all streams of which move at the same or approximately the same speed. It is not possible to make any precise distinction between the lines of water flow in the pores of various rocks, therefore, when considering issues of groundwater movement, we can only talk about the average speed of water movement within a particular medium. Determination of the speed of movement of groundwater (actual speed Vd) is carried out in the field. For determination, indicators are used that change the color or chemical composition and electrical conductivity of water.

To conduct experiments, two wells (pits), sometimes four, are selected, located along the direction of water movement. The workings located upstream serve to introduce the indicator into the water; it is called experimental. The workings located downstream are called observation. The distance between them is selected depending on the rocks from 0.5-1.5 to 2.5-5.0 m. Dyes (fluorescence, etc.) are used as an indicator. In addition, table salt is used as an indicator (chemical method), there are radio indicator methods, the method of natural isotopes, etc. The geophysical method is widely used - the method of equipotential lines (charged body method). The values ​​of the actual speed of movement (Vd) can be used to calculate the filtration coefficient of rocks, when deciding on the issue of suffusion under structures, etc.

To identify the direction of movement of groundwater over large areas, hydroisohypsum and hydroisopiesis maps are drawn up. When solving hydraulic engineering and drainage problems (irrigation, drainage), hydroisohypses are constructed and, on their basis, maps of groundwater depths are constructed. The direction of groundwater flow is perpendicular to the hydroisohypses.

IV. Basic hydrogeological parameters.

The most important properties of rocks are filtration, which are characterized by the following parameters: filtration coefficient, permeability coefficient, water loss coefficient, water conductivity, conductivity level coefficient, etc.

Filtration coefficient (K)represents the most important characteristic of rocks, is widely used in design practice when calculating groundwater flow, when determining water losses from reservoirs, ponds, etc. The filtration coefficient of rocks can be determined from data on the composition and porosity of rocks (using empirical formulas), laboratory methods, and in the field.

Determination of rock coefficients using empirical formulas. Experimental work has established the dependence of the coefficient on the mechanical (granulometric) composition of the rock (mainly on the size and number of fine fractions), its porosity, and water temperature. Determining the rock coefficient by particle size distribution is the cheapest and simplest method used in hydrogeological surveys for the initial stages of design. For detailed studies, this method is additional to the field method. The Hazen formula is used (for sands with a diameter from 0.1 to 3 mm, with a uniformity coefficient l less than 5). The uniformity coefficient is the ratio of grain size. Effective diameter (d 10 ) is the particle diameter in mm, less than which the soil contains 10% of the total mass of the soil. In other words, dn is equal to the diameter of the sieve opening that allows 10% of the soil mass to pass through.

Hazin's formula

K=Сdн 2 (0.70+0.03t), m/day,

C is an empirical coefficient depending on the degree of homogeneity and porosity of the soil. For clean, homogeneous sands C=1200, average homogeneity and density C=800, heterogeneous and dense sands C=400,

dн – effective diameter, mm,

t is the temperature of the filtered water.

The values ​​of d60 and dn are taken from the soil granulometric composition curve and drawn in the form of a curve on a simple or semi-logarithmic scale.

Sauerbrey formula for water temperature 10º

M/day

β – empirical coefficient depending on the uniformity and size of sand particles from 1150 to 3010, average 2880-3010

n – porosity

d17 – particle diameter in mm, less than which 17% of particles by weight are present in a given soil. Used to determine the coefficients of fine, medium and coarse sands.

Determination in laboratory conditions. Various devices are used to load test samples of rocks with disturbed and natural structure. The principle of determining coefficients in most devices is based on measuring the amount of water filtered through the rock under different pressures. Based on the flow rate at a known pressure and area of ​​the device, the filtration coefficient is found. Kamensky tubes, Tom's device, etc. are used.

It is necessary to remember well that the filtration coefficients of rocks of the aeration zone, determined in natural field conditions and by laboratory methods, often differ by up to 1-2 orders of magnitude. This is explained by the underestimation of rock anisotropy and the small area of ​​the identified rocks.

Determination in the field. When determining the filtration coefficient in the field, water movement occurs in rocks that occur in natural conditions and preserve their natural structure. Therefore, field methods give results that are closest to reality. Methods of filling into pits and wells in the aeration zone are used. Within aquifers, the coefficient is determined by pumping from wells and pits.

Method of pouring into pits.The process of infiltration into soils unsaturated with water is very complex and occurs with the simultaneous action of the hydraulic pressure of water poured into the pits and capillary suction of water into the soil. Currently, the filling method according to N.S. is often used. Nesterov.

M/day

Q – steady water flow, m 3 ;

F – bottom area of ​​the small ring, m 2 ;

More precisely, the value of Kf is determined:

l – depth of water infiltration from the bottom of the pit;

z – height of the water layer;

h k – capillary pressure equal to ≈50% of the maximum height of capillary rise, m

According to Nesterov's method2 steel rings with a diameter of 25 and 50 cm are installed in the bottom of the pit to a depth of 3-4 cm. Water is poured into the ring and a layer of 10 cm is maintained at a height of 10 cm. The experiment continues until the flow rate stabilizes.

Experimental injections are widely used to determine the Kf of non-water-bearing fractured and karst rocks at different levels, isolating the intervals with special tampons. The experiment is carried out until the water flow stabilizes. As a result of the experiment, the specific water absorption is determined (q = l/min), i.e. water consumption in l/min per 1 m of well and 1 m of pressure according to the formula:

P – pressure on the manometer,

H – vertical distance from the pressure gauge to the tampon, m,

Z – length of the studied interval (between tampons).

Approximate values ​​of Kf (m/day):

Clay – 0.001, in the aeration zone up to 0.3-0.7;

Loam – 0.05, in the aeration zone 0.5-1;

Sandy loam – 0.1-0.5 in the aeration zone up to 1-2;

Sand – from 1-5 to 20-50;

Gravel – 20-150;

Pebble – 100-500 or more.

The water permeability of clayey rocks depends on the content of exchangeable cations. Ca and Mg increase water permeability, and Na decreases it. This value changes depending on the temperature. When filtering fresh water, clay particles swell and Kf decreases, while salt water, especially sodium chloride water, Kf increases, because clay particles do not swell, salts crystallize and porosity increases.

When the specific water absorption is less than 0.01 l/min, it is generally accepted that the rocks are slightly fractured and cementation is not required to combat filtration. Based on specific water saturation, one can find

Where r is the well radius, m

For determination, express methods of filling and pumping from wells and pits are usually used approximately and quickly. They make it possible, with mass sampling in a short period of time, to characterize the filtration properties of sediments over a large area. They are suitable mainly for the purpose of extrapolating data obtained at cluster pumping sites to the corresponding territory.

The most accurate data on the filtration coefficient, as well as other parameters, are obtained when pumping from wells of various durations.

Water loss of rocks(B) the property of rocks saturated with water to freely give up gravitational water. The amount of water loss is characterized by the water loss coefficient - the ratio of the volume of flowing water that previously filled the voids to the volume of the entire rock. Expressed as a percentage or fraction of a unit volume and is a variable value. The water loss coefficient of pebbles, gravel, and coarse sands is equal to their porosity or total moisture capacity. The water yield of clayey rocks and peat is equal to the difference in the total minimum moisture capacity.

The water loss coefficient is determined: 1) by the difference between different moisture capacities; 2) by saturating the rock and draining the water; 3) field observations, the method of pumping groundwater from wells, etc.

Water yield (%) of some rocks: sand c/z - 0.25-0.35, c/z - 0.2-0.25, m/z - 0.15-0.2, sandy loam 0.1-0 .15, loams less than 0.1, clays close to 0, peat 0-0.15, sandstones - 0.02-0.05, limestones - 0.008-0.1.

To solve a number of practical problems, the coefficient of lack of saturation (µ) is widely used; it is equal to the difference between the total moisture capacity and the natural moisture of the rock before infiltration, expressed in fractions of a unit volume.

Water conductivity– the ability of an aquifer with a thickness (W) and a width of 1 m to pass water per unit time with a pressure gradient = 1. Water conductivity (T) is equal to the product of Kf (filtration coefficient) and the thickness of the formation T=KW and is expressed in (m/day). The larger (T), the greater the operational resources of groundwater. T>100 m 2 /day T 2 /day the water horizon is unpromising for use for water supply purposes.

Experimental filtration work is widely used to determine hydrogeological parameters. These methods are based mainly on the equations of unsteady movement of groundwater in the zone of influence of pumping. These patterns are determined by the filtration and capacitive properties of the studied aquifer, which makes it possible to estimate water conductivity, filtration coefficient, conductivity level, lack of saturation, water yield, etc. When the patterns of groundwater movement are determined not only by filtration and capacitance properties, but also by boundary conditions, the parameters are calculated using the formulas steady motion. Experimental pumping is divided into single and cluster.

Single pumpings (without observation wells) are carried out at several stages of reduction to find the dependence of the well's flow rate on the decrease in the groundwater level.

Cluster pumping is carried out by equipping the experimental area with observation wells, located one or two at a time to the central well from which pumping is carried out. During pumping, the well flow rate and the decrease in water level in the central and observation wells are measured. The main purpose of cluster pumping is to determine the calculated hydrogeological parameters.

In difficult conditions, when it is necessary to study the relationship of aquifers or the effectiveness of a vertical drainage well, etc., experimental pumping is carried out. The duration of pumping varies from a day to 30-40 days or more. The method of pumping depends on the purpose of pumping and the hydrogeological conditions of the area.

To determine the filtration coefficient, pumping is carried out at a constant flow rate (changing water level in the well and funnel, which corresponds to an unsteady filtration mode), or at a constant decrease in level (steady filtration mode). To establish the dependence of the flow rate on the decrease, pumping is carried out at 2-3 decreases in level.

To assess the water permeability of multilayer aquifers, characterized by interlayering of aquifers and weakly permeable separating layers, each aquifer is tested separately. At the same time, the values ​​of flow from the lower and upper aquifers through low-permeability clay layers are determined.

The flow coefficient (B) is determined by the formula:

Km – water conductivity of the main water horizon m 2/day,

K1, K11 – respectively, rock filtration coefficient, m/day,

m 1, m 11 – thickness of these layers, m.

Determination of groundwater flows.

1) Flat flow and its flow rate.Flat is a flow of groundwater whose streams flow more or less parallel. An example would be the flow of groundwater moving towards a river. The ground flow rate in a horizontal aquifer per 1 m width is equal to

With an inclined aquitard, the unit flow rate of the underground flow is equal to:

Types of vertical catchments.

Vertical catchments can be divided into wells (pits) and boreholes. Based on the nature of the exploited aquifers, they are divided into groundwater and artesian (pressure). Based on the nature of their location in the aquifer, wells (wells) are divided into perfect and imperfect. Imperfect wells can have a permeable bottom and walls, permeable walls and a solid bottom, and solid walls and a permeable bottom (Fig. 3).

Rice. 3. Diagram of water flow into an imperfect well

Perfect wells penetrate the entire aquifer and have permeable walls. The choice of design equations for the movement of water to the wells depends on the type of vertical catchment.

Flow rate of a perfect well and rock filtration coefficient

– Dupuis formula, m 3 /day, from here

M/day

The flow rate of a well with an open flat bottom is calculated according to Forchheimer:

Q=4rSK, m 3 /day.

Filtration coefficient, m/day.

Flow rate of a well with permeable walls and an open bottom

M 3 / day,

M/day

According to Zamarin, for a well with an open bottom and permeable walls (provided that the aquifer depth is unknown) with a flat bottom, Kf is calculated (see Fig. 3):

M/day, where

Q – well flow rate, m 3 /day

Formula for water flow into drains.

Drains are constructed to lower the groundwater level. The influx of water into a perfect horizontal drain of length B under conditions of non-pressure water according to the Dupuis equation is equal to

M 3 /day.

For pressure, m 3 /day;

m – thickness of the pressure layer, m.

Calculation formulas show the dependence of well flow rate on decrease (S). Therefore, well productivity can be compared by specific flow rate

Lecture 3. Chemical composition of groundwater

Plan:

Physical properties of groundwater

Water reaction

General water mineralization

Chemical composition of water

Forms of expressing the chemical composition of water

Assessing the suitability of water for various purposes

Assessment of the aggressiveness of groundwater properties

Formation of the chemical composition of groundwater

Groundwater zonation

I. On physical propertiesgroundwater include transparency, color, smell, taste, temperature.

Natural water can be clear or cloudy. Water turbidity is caused by the presence of suspended particles of mineral and organic origin. Mechanical impurities can enter the source water due to a malfunction of the water intake or seepage of rain, floodwater, or river water (karst areas) into the aquifer. Sometimes the turbidity of groundwater is caused by chemical compounds dissolved in it (iron, etc.).

Color. Pure water is colorless. The color is explained by the presence of certain impurities in it (iron gives a rusty tint, hydrogen sulfide gives a bluish tint).

Smell. Groundwater is usually odorless. The presence of an odor indicates the presence of various chemical compounds (hydrogen sulfide gives the smell of rotten eggs, etc.)

Taste. Appears at a certain content of certain compounds in water (salty - NaCl, acidic - in areas of sulfide deposits).

Temperature – varies from 4-5ºС to 60-90ºС. At temperatures above 20ºС, waters are called subthermal. In the Republic of Bashkortostan, the temperature of shallow groundwater ranges from 5 to 20ºС. Fresh water at tº=4ºС has the highest density.

II. Water reaction (pH value). In order to judge the chemical composition of groundwater, it is necessary first of all to know the reaction of water, i.e. concentration of hydrogen ions. According to the theory of electrolytic dissociation, water dissociates into hydrogen () and hydroxyl () ions, the value of the product of which is always constant at a given temperature. If the reaction is neutral, then the concentration is the same and equal to 10–7 mEq/L Therefore, the degree of acidity or alkalinity of water is characterized by the concentration of hydrogen ions. To express the concentration of hydrogen ions, it is customary to use the logarithm of their concentration (i.e., the number of gram-equivalents of this ion in 1 liter of water), taken with the opposite sign and denoted pH = –log(H+ ). With a neutral reaction, pH = 7, with an acidic pH - less than 7, and with an alkaline pH more than 7. Determination of pH is carried out with special devices (pH meters) using the calorimetric method; in the field, litmus paper is used.

III. General water mineralizationis expressed by the sum of the chemical elements contained in water, their compounds and gases. It is estimated by the dry residue, which is obtained after evaporating water at a temperature of 105ºC, or by summing the mass of all ions obtained from chemical analysis. Expressed in milligrams (grams) per liter (dm 3 ), grams per kg (mg/l, g/kg). According to mineralization they are divided into:

up to 0.2 g/l – ultra-fresh, up to 1.0 g/l – fresh,

1-10 – brackish: 1-3 – slightly, 3-5 – medium, 5-10 – highly brackish, 10-35 – salty, more than 35 g/l – brines.

IV. The main chemical components in groundwaterusually are: anions (hydrocarbonate ion, sulfate ion, chlorine ion), cations (). Water often contains carbonate ion, nitrite ion, nitrate ion (), carbon dioxide, hydrogen sulfide, methane, 2- and 3-valent iron, etc. The content of nitrogen compounds in groundwater is usually low (1-2 mg/ l), but sometimes reaches 0.5-0.8 mg/l. The presence of even a small amount of them indicates contamination of the water and the possibility of harmful dangerous bacteria being found in it. If nitrite ion () is present, the contamination is fresh, and nitrate ion is the contamination is old. In general, groundwater contains up to 60-80 different chemical elements in a dissolved state.

Hardness of water due to the presence of calcium and magnesium ions. According to GOST 2874-73 and SanPiN 2.1.4.1074-01, water hardness is expressed in milligram equivalents per 1 liter of water. 1 mEq. hardness corresponds to a content of 20.04 mg/l and 12.6 mg/l. According to water hardness, they are divided into:

very soft – up to 1.5 mEq/l,

soft – 1.51-3.0 mEq/l,

moderately hard – 3.01-6.0 mEq/l,

hard – 6.01-9.0 mEq/l,

very hard – more than 9.0 mEq/l.

V. There are several forms of expressing water analysis:ionic, equivalent, percent-equivalent.

In the ionic form, the ion content is given in grams or milligrams per liter (g/l, mg/l).

The equivalent form allows us to judge possible combinations of cations and anions. The sum of equivalent units of cations and anions is expressed in milligram equivalents per 1 liter and is obtained by multiplying mg/l by the conversion factor (Tables 1, 2).

Table 1

Atomic weights of ions and factors for converting milligram ions to milligram equivalents

K+

39,100

0,02558

Na+

22,997

0,04348

NH4+

18,040

0,05543

Ca2+

20,040

0,04990

Mg 2+

12,160

0,08224

Cl –

35,457

0,02820

NO 3 –

62,008

0,01613

NO 2 –

46,008

0,02174

eq

51,5

48,1

In the percentage equivalent form, the content of ions, taken in equivalents, is expressed as a percentage of the sum of cations and anions, each taken as 100%.

A visual form for recording the results is the formula of M.G. Kurlova.

The name of water is given by the predominant anions and cations, the content of which is more than 20% (sometimes 25% or 33%) in ascending order. For example, the given formula reads: sulfate-hydrocarbonate, magnesium-calcium water.

In the Kurlov formula, to the left of the line indicate the gas content (CO 2 , H 2 S, etc.), total mineralization of water (g/l), in the numerator are anions, the content of which exceeds 10% equivalents (% equivalents in descending order) in the denominator - cations in the same order, the tºC of water is written behind the line, flow rate (l /s), pH and others. The results of chemical analysis of water are sometimes expressed in graphical form in the form of diagrams - rectangle, square, triangle, etc. All forms of expression and construction methods are given in (Abdrakhmanov, Methodological..., 2008).

Classification of groundwater by chemical composition.There are several dozen classifications based on different principles and having different practical applications and meanings. The most popular classifications include Palmer, N.I. Tostikhina, V.A. Sulina, O.A. Alekina, E.V. Posokhova and others. In hydrogeology and hydrology, the hydrochemical classification of O.A. is mainly used. Alekina.

All natural waters are divided into three classes according to the predominant anion: 1) hydrocarbonate, 2) sulfate, 3) chloride. The identified 3 classes immediately give an outline of the hydrochemical appearance of water. The hydrocarbonate class includes most of the fresh (low-mineralized) waters of rivers, lakes, and some groundwater. The chloride class includes waters of the ocean, seas, and underground waters of deep horizons. Waters of the sulfate class are intermediate in distribution and magnitude of mineralization between hydrocarbonate and chloride.

Each class is divided by O.A. Alekin according to the predominant cation into groups of calcium, magnesium and sodium waters. In addition, all waters are combined into types, 4 types of waters are distinguished.

The first type is characterized by the ratio (NHCO 3 – soda)

Type II (sodium sulfate)

III type or subdivided:

On III a (–magnesium chloride) and

III b (– calcium chloride).

As has been established, the ionic form is characteristic only of low mineralization waters. As the concentration of dissolved salts increases, interactions are established between the ions. Neutral ions, etc., are formed in the solution.

Due to the complexity of the chemical composition of natural waters, when assessing drinking, medicinal, technical, reclamation and other qualities, it is important to take not only the absolute content of individual ions, but also the expected associations of anions and cations (salts). They are calculated according to the Fresenius rule (slightly soluble salts precipitate first, then more soluble ones).

VI. Assessing the suitability of water for various purposes.

Water supply. According to GOST 2874-73 “Drinking water” and SanPiN 2.1.4.1074-01, water must meet the following requirements: Mineralization up to 1 g/l (according to the SES rating up to 1.5 g/l); hardness 7 mEq/l. up to 350 mg/l; up to 500 mg/l (Abdrakhmanov, Chalov, Abdrakhmanova, 2007).

Irrigation. Irrigation water, in terms of mineralization and chemical composition, must be physiologically accessible to plants and not cause salinization and alkalinization of the soil. It is important to study the content of microcations of biologically active microelements: I, Br, B, Co, Cu, Mn, Mo (Abdrakhmanov, Methodological..., 2008).

VII. Aggressive properties of groundwater.They mean the ability of water to destroy various building materials, affecting them with dissolved salts, gases or leaching their components. Of particular importance is the aggressive effect of water on concrete structures. The main binder in concrete is cement. The practical significance of the aggressive effect of water on the concrete of a structure is so great that not a single significant construction can be completed without a preliminary hydrochemical study of the aquatic environment. According to CH-249-63, the following types of aggressive action of water on concrete are distinguished: leaching, carbon dioxide, general acid, sulfate, magnesia.

The aggressiveness of leaching is manifested in the dissolution of calcium carbonate, which is part of the concrete. It is possible with a low content in water (0.4-1.5 mg-eq/l) and the excess dissolves.

Carbon dioxide aggressiveness is due to its effect on concrete.

In the most dangerous conditions, the maximum permissible content of aggressive carbon dioxide () is 3 mg/l, in less dangerous conditions up to 8.3 mg/l.

General acid aggressiveness is characteristic of acidic waters and depends on the content of free hydrogen ions. At pH 5.0-6.8 this type of aggression is possible.

Sulfate aggressiveness manifests itself when there is a high content of ions, which, penetrating into the body of concrete during crystallization, form salts. The formation of these salts in the pores of concrete is accompanied by an increase in their volume and destruction of concrete. Aggressiveness manifests itself with ordinary cements at more than 250 mg/l, with sulfate-resistant cements - 4000 mg/l.

The magnesium type of aggressiveness manifests itself, just like the sulfate type, in the destruction of concrete when water penetrates into the body of the concrete. This species occurs at high levels. Depending on the cement, it appears at a magnesium content of 1.0 to 2.5 g/l.

VIII. Formation of the chemical composition of groundwater.Factors in the formation of the chemical composition of groundwater are understood as the driving forces that determine the course of various processes that change the mineralization and chemical composition of water. The chemical composition of groundwater is formed under the influence of the following factors: leaching of soils and rocks, complete dissolution of minerals and rocks, concentration of salts in water as a result of evaporation, precipitation of salts from natural solutions when thermodynamic conditions change, cation exchange in the absorbing complex of silts, soils, clayey rocks (on and on), diffusion and microbiological processes, mixing of waters of different origins. The exchange process is observed between cations of clay rocks - water and depends on the capacity of the absorbing complex (Table 3).

Table 3

Absorption capacity of some clay minerals

These processes depend on climatic, geomorphological, geological, hydrodynamic and other conditions. The composition of precipitation plays a significant role in the formation of the chemical composition of groundwater. The role of atmospheric precipitation in the formation of the composition of low-mineralized waters is well known. A significant amount of dissolved salts comes from the atmosphere to the earth's surface. In the Republic of Bashkortostan, the anionic composition of rainwater is dominated by hydrocarbonate ions (41-85%), less often sulfate and chloride. Among the cations, sodium predominates (40-75%), calcium is less common. The mineralization of rainwater ranges from 23 to 88 mg/l, pH -6.0-6.7, – 9-16 mg/l, the mineralization of snow water is 19-54 mg/l. According to calculations per 1 km 2 The territory of Bashkortostan receives 25-27 tons of salts per year. On the territory of the European part of the USSR reaches 50-85 per 1 km 2 .

Precipitation gradually infiltrates deeper and becomes saturated with salts in the soil horizon and then in the aeration zone. This occurs as a result of the dissolution of salts, minerals, rocks in accordance with their solubility. Solubility varies widely, depending on water temperature and the content of other salts. The solubility of salts in distilled water at 7ºС is (g/l) – 0.013, – 2.01, – 193.9, – 168.3, – 358.6, – 329.3, – 354.3, – 558.1 . Solubility in the presence increases 4 times. If there is CO in the water 2 the solubility of carbonates increases.

In loose cover formations, the first soil-type aquifers from the surface are formed. Analysis of aqueous extracts from rocks of the aeration zone indicates that when they are exposed to atmospheric waters that have a slightly acidic reaction, salts from the aeration zone are observed. The main salts entering groundwater are calcium carbonates and sulfates and magnesium carbonates. Excess potassium nitrate, which is used in the fields as fertilizer, is removed from the soil. The content reaches 200 mg/l.

In the steppe regions of Russia, as a result of evaporation, a large amount of salts accumulate in the aeration zone. The closer to the surface groundwater is located, the higher, other things being equal, its mineralization. With shallow groundwater up to 1 m, salt accumulation is possible on the surface of the earth. In desert and semi-desert areas, groundwater with high mineralization (up to 10-20 or more) of sulfate-chloride and chloride composition is often formed.

Bicarbonate calcium waters (form) are formed by the dissolution of calcium carbonates (limestones). Calcium sulfate waters when dissolving gypsum. Hydrocarbonate sodium waters as a result of cation exchange between water of hydrocarbonate-calcium composition + absorption. soil Na complex. soil.

A favorable environment for the reaction to occur is created in irrigated fields.

When salting with soda, to convert soda into less harmful salt, add

Anions and cations. Primary sources of anions and cations.

The primary sources of the mineral composition of natural waters are:

1) gases released from the bowels of the earth during the process of degassing.

2) products of the chemical action of water with igneous rocks. These primary sources of the composition of natural waters still exist today. Currently, the role of sedimentary rocks in the chemical composition of water has increased.

The origin of anions is mainly associated with gases released during degassing of the mantles. Their composition is similar to modern volcanic gases. Along with water vapor, gaseous hydrogen compounds of chlorine (HCl), nitrogen (), sulfur (), bromine (HBr), boron (HB), carbon () enter the atmosphere. As a result of phytochemical decomposition of CH 4 CO 2 is formed:

Saturation

As a result of the oxidation of sulfides, an ion is formed.

The origin of cations is associated with rocks. Average chemical composition of igneous rocks (%): – 59, – 15.3, – 3.8, – 3.5, – 5.1, – 3.8, – 3.1, etc.

As a result of rock weathering (physical and chemical), groundwater is saturated with cations according to the following scheme: .

In the presence of acid anions (carbonic, hydrochloric, sulfuric), acid salts are formed: .

Microelements. Typical cations: Li, Rb, Cs, Be, Sr, Ba. Heavy metal ions: Cu, Ag, Au, Pb, Fe, Ni, Co. Amphoteric complexing agents (Cr, Co, V, Mn). Biologically active trace elements: Br, I, F, B.

Microelements play an important role in the biological cycle. The absence or excess of fluoride causes the diseases caries and fluorosis. Lack of iodine – thyroid disease, etc.

Chemistry of atmospheric precipitation.Currently, a new branch of hydrochemistry is developing - atmospheric chemistry. Atmospheric water (close to distilled) contains many elements.

In addition to atmospheric gases (), the air contains impurities released from the bowels of the earth components (etc.), elements of biogenic origin () and other organic compounds.

In geochemistry, the study of the chemical composition of atmospheric precipitation makes it possible to characterize the salt exchange between the atmosphere, the surface of the earth, and the oceans. In recent years, due to atomic explosions, radioactive substances have been released into the atmosphere.

Aerosols. The source of the formation of the chemical composition are aerosols:

dusty mineral particles, highly dispersed aggregates of soluble salts, tiny drops of solutions of gas impurities (). The sizes of aerosols (condensation nuclei) are different - the radius averages 20 μm (cm) and fluctuates (up to 1 μm). The quantity decreases with height. The concentration of aerosols is maximum within urban areas and minimum in the mountains. Aerosols are lifted into the air by the wind - aeolian erosion;

salts rising from the surface of oceans and seas, ice;

products of volcanic eruptions;

human activity.

Formation of chemical composition. A huge amount of aerosols rises into the atmosphere - they fall to the surface of the earth:

in the form of rain,

gravitational sedimentation.

Formation begins with the capture of aerosols by atmospheric moisture. Mineralization ranges from 5 mg/l to 100 mg/l or more. The first portions of rain are more mineralized.

Other elements in sediments:

– from hundredths to 1-3 mg/l. Radioactive substances: etc. They come mainly from testing atomic bombs.

Mineral water

The healing properties of mineral waters are determined by: mineralization, ion-salt composition, content of biologically active components, gas and redox potential (Eh), active reaction of the environment (pH), radioactivity, temperature, hydrogen sulfide content ().

Minimum concentration of elements for mineral medicinal waters (mg/l): hydrogen sulfide – 10, bromine – 25; iodine 5, fluorine – 2, iron – 10, radon – 14 units. Mahe.

Industrial waters include waters containing components of at least:

Table 4

Regulatory requirements for mineral industrial waters

Lecture 4. Zoning of groundwater

Zoning of groundwater manifests itself on a global scale and belongs to the category of fundamental properties of the hydrolithosphere. It is understood as a pattern in the spatio-temporal organization of the underground hydrosphere, a certain direction of change in hydrogeodynamic, hydrogeochemical, hydrogeothermal and hydrogeochronological parameters.

In the sedimentary cover, for example, of the Volga-Ural basin, two hydrogeochemical levels are distinguished, which in their volume generally correspond to hydrogeodynamic levels. The upper floor (300–400 m, rarely more) contains predominantly infiltrative oxygen-nitrogen (nitrogen) waters of various ion-salt compositions with mineralization usually not exceeding 10–12 g/l. Within the lower floor lie high-pressure, mainly chloride brines of various origins (sedimentogenic, infiltogenic, mixed) with salt concentrations of up to 250–300 g/l or more, and water-dissolved gases (H 2 S, CO 2, CH 4, N 2 ) correspond to a reducing geochemical environment, conditions of very difficult water exchange and a quasi-stagnant regime of the subsoil. Within the floors, according to the chemical composition and degree of mineralization, four zones are distinguished - hydrocarbonate, sulfate, sulfate-chloride and chloride, which in turn are divided into a number of subzones (Fig. 4).

The zone of fresh (up to 1 g/l) hydrocarbonate waters is confined to rocks of a wide age range (from Quaternary on the platform to Devonian on the western slope of the Urals) and in hydrogeodynamic terms corresponds to a zone of intense circulation. Its thickness (H) ranges from 20–50 m in river valleys to 150–200 m on watersheds, and on the Ufa plateau reaches 500–800 m. The speed of water movement (v), depending on the filtration properties of rocks and the hydraulic gradient, varies from tens and hundreds of meters to tens of kilometers per year, and the period of complete water exchange (t) is from tens to a few hundred years.

Rice. 4. Hydrogeochemical section of the Southern Urals

1–9 – chemical composition and mineralization of groundwater, g/l: 1 – calcium bicarbonate (up to 0.5), 2 – sodium bicarbonate (0.5–1), 3 – hydrocarbonate, less often sulfate-hydrocarbonate and chloride-bicarbonate of various cationic composition (up to 1), 4 – calcium sulfate (1–3), 5 – sodium sulfate and calcium-sodium (3–10, rarely more), 6 – sulfate-chloride (3–10), 7 – sulfate-sodium sodium chloride (10–36), 8 – sodium chloride (36–310), 9 – calcium-sodium and sodium-calcium chloride (250–330); 10 – relatively waterproof halogen rocks of Kungur; 11–13 – boundaries: 11 – hydrogeochemical, 12 – stratigraphic, 13 – upper limit of the distribution of hydrogen sulfide in groundwater; 14 – well: a – on the profile line, b – designed for it (figure – water salinity (g/l) in the tested interval), 15 – bromine content isolines, 16 – hydroisotherms.

Within the hydrocarbonate zone, two subzones are distinguished: the upper - calcium (magnesium-calcium) and the lower - sodium waters. The thickness of the latter usually ranges from 20 to 100 m and rarely more (Yuryuzano-Ai depression). The mineralization of sodium bicarbonate (soda) waters is usually 0.5–0.9 g/l, but in some cases reaches 1.2–1.7 g/l. Genetically, pure soda waters are closely related to terrigenous essentially clayey Permian formations, represented by interbedded sandstones, siltstones, mudstones and clays. They have rather low filtration properties and low water abundance. The gas composition of hydrocarbonate waters corresponds to the oxidizing geochemical environment: N 2 30–35, CO 2 5–30, O 2 up to 10 mg/l. Gas saturation is usually 15–50 ml/l, Eh +100…+650 mV, pH 6.7–8.8, T 4–6 C. Helium content (He) corresponds to atmospheric (5×10–5 ml/l).

The zone of sulfate brackish and saline waters is developed everywhere, excluding pockets of natural and man-made (areas of some oil fields) influence of deep brines. It includes sulfate and hydrocarbonate-sulfate classes of waters with mineralization from 1–3 to 15–20 g/l, formed in an oxidizing geochemical environment mainly in Permian gypsum deposits. In hydrogeodynamic terms, it corresponds to both a zone of intense circulation (above the incision of the erosion network) and a zone of difficult water exchange, where the speed of groundwater movement decreases to tens of meters per year, and the time of complete water exchange, on the contrary, increases to hundreds and thousands of years.

The depth of sulfate water varies from 0 to 250 m or more. The average thickness of the zone is about 100–150 m (see Fig. 4). Within the zone are the main resources of medicinal drinking water of infiltration origin, the leading role in the formation of the composition of which is played by the processes of extraction of gypsum from rocks and ion exchange phenomena with the participation of the absorbed complex of rocks.

The oxygen-nitrogen and nitrogen composition of sulfate waters is formed due to the entry of air gases along with infiltration waters, and only in rare cases, when the base of the zone is deeply immersed and its thickness is high, is H present in the gas phase 2 S, genetically associated with biochemical processes in sulfated and bituminous Permian rocks. O concentration 2 down the section of the zone, due to its consumption on the oxidation of organic matter, iron, and sulfides, it decreases from 4–5 mg/l to zero, and the Eh value decreases from +250 to –150 mV. Acid-base potential pH varies from 7.3 to 8.8; T 4–10 C. Helium content increases (up to 30–100×10–5 ml/l)

According to the cationic composition, the waters of the sulfate zone belong to two main groups - calcium (magnesium-calcium) and sodium (calcium-sodium), corresponding to the hydrogeochemical subzones of gypsum and Glauberian waters.

The mineralization of waters in the upper subzone usually does not exceed 2.5–2.6 g/l. These are typical leaching waters of gypsum, gypsumed terrigenous and carbonate rocks, which are dominated by sulfate ion (up to 80–90%), calcium and magnesium (up to 90–98% in total). The thickness of the subzone varies from 10 to 100 m.

Sulfate sodium waters of the lower subzone are confined to exclusively terrigenous gypsum-bearing Permian sediments of lagoonal-marine origin, lying below the bottoms of the main rivers of the region. They are most developed in the Upper Permian deposits in the west of the region, where the depth of the roof of the subzone varies from 10–20 m in river valleys to 200 m on watersheds. Its thickness is on average 100 m. In the Cis-Ural basin, sulfate sodium waters are opened at a depth of 100–300 m; The thickness of the subzone here can reach 120–150 m.

The mineralization of sodium sulfate waters ranges from 1.4 to 20, usually 3–10 g/l, and it increases with depth. With a mineralization value of up to 6.0–6.5 g/l, the cationic composition of water is usually calcium-sodium or mixed (three-component). In more mineralized waters, the leading role among cations belongs to sodium (up to 85–90%), which in absolute terms is 4–5 g/l. The formation of sodium sulfate waters is due to two interrelated and interdependent processes that stimulate each other: extraction of CaSO 4 and exchange adsorption between the calcium of the solution and the sodium of the absorbed rock complex.

The zone of sulfate-chloride waters with a salinity of 5–36 g/l, like the one lying above, is associated mainly with Permian deposits and is characterized by conditions of a difficult hydrogeodynamic regime. Geochemically, the zone occupies an intermediate position, differing in redox conditions (Eh from +100 to 180 mV; pH 6.7–7.5), atmospheric gases (O 2, N 2 ) and biochemical (H 2 S) origin. Therefore, depending on the gas composition, mineral sulfate-chloride waters can be used either for medicinal drinking or for balneological purposes.

To the east of the meridian of the city of Ufa, in the marginal part of the Volga-Kama basin and in the Pre-Ural basin, hydrogen sulfide sulfate-chloride waters (5–30 g/l) are established in carbonate and terrigenous-carbonate deposits of the Lower Permian age, and in the Western Ural basin - in Carboniferous and Devonian carbonate deposits. The thickness of the zone here reaches 250 m.

The zone of chloride brines is developed everywhere, occupies the largest interval of the hydrogeochemical section (from 3 km on the Ufa Plateau to 10–11 km in the Pre-Ural Trough) and completely corresponds to the lower level of the artesian basin.

The zone contains two main subzones: sodium (CaCl 2 less than 20%) and sodium-calcium (CaCl 2 up to 50–70%, or 100–150 g/l) brines. These subzones differ not only in the general ion-salt composition, but also in the microcomponent and gas composition of waters, as well as hydrogeodynamic conditions.

The main gas components of the lower subzone - CH 4 and N 2. H 2 There is no S in it. On the contrary, N 2 S is an obligatory component of the gas composition of brines in the upper (sodium) subzone. One of the indispensable conditions for the biochemical generation of H 2 S is known to be the mobility of groundwater, ensuring the dissolution of CaSO 4 and the activity of sulfate-reducing bacteria. This circumstance, as well as data on the degree of metamorphization of brines (rNa/rCl), the values ​​of the bromine gradient (Br/H), the coefficients Br/M, He/Ar, give grounds to associate the upper subzone with conditions of very difficult water exchange, and the lower subzone with conditions of quasi-stagnant water regime.

Lecture 5. Geological activity of groundwater

Plan:

Karst

Rock fracturing

Suffusion

I. Karst. According to the definition of D.S. Sokolova (1962) karst is the process of breaking down and destroying permeable soluble rocks primarily through leaching by moving waters. Karst rocks are distinguished - salt rocks (their area in the world is 4 million km 2 ), gypsum anhydrite (7 million km 2 ) and carbonate rocks (40 million km 2 ). There are salt karst, gypsum, carbonate. For karst to form, the following conditions must be present:

the presence of soluble rocks,

the presence of cracks that make it possible for water to circulate in rocks,

presence of moving waters,

dissolving power of moving waters.

Only when these conditions are combined does karst form.

Main karst forms:

cracks, karst sinkholes, wells, blind ravines, valleys, etc.,

karst caves, canals and other large karst cavities,

cavities and secondary porosity.

According to the degree of overlap of karst rocks, subclasses of closed, covered, covered and bare karst are distinguished. Almost 50% of the territory of Bashkortostan is karst (Fig. 5, Table 5).

Rice. 5. Karst zoning scheme

For symbols, see table. 5

Table 5

Zoning of karst in Bashkortostan

End of table 5

II. Rock fracturing.Fracture is a form of disruption of rock continuity, widespread in sedimentary, igneous and metamorphic formations of the earth's crust. Fracture is an important factor determining the water permeability of rocks.

In accordance with the well-known classification by D.S. Sokolov there are four categories of cracks: lithogenetic, tectonic, unloading and weathering.

Lithogenetic cracksare formed during the process of lithogenesis due to the internal energy of rock (sediment). Their distinctive feature is their localization within a given layer (intralayer cracks); their direction can be different: parallel to the bedding, perpendicular or inclined to it.

Tectonic cracksare the result of stresses and movements of the earth's crust, forming plicative (folded) and disjunctive (discontinuous) deformations of rocks. They are divided into two types: intralayer and cutting several layers. Tectonic and lithogenetic intralayer cracks are very similar and therefore practically difficult to distinguish.

Unloading and weathering cracksbelong to the exogenous group. They, as a rule, are superimposed on a lattice of pre-existing fractures of endogenous origin (lithogenetic and tectonic) and on planetary fracturing.

The knowledge of fracturing in rocks of Bashkortostan is not the same in different regions. The greatest completeness of information on this issue is available for the sedimentary cover of the platform territory of the Southern Urals (Western Bashkortostan), where fracturing was studied in the process of hydrogeological surveys, exploration and exploitation of oil fields, and searches for water supply sources. The fracturing of rocks in the folded mountain region of Bashkortostan has been poorly studied.

Among the cracks in the rocks of the platform region of Bashkortostan, tectonic, lithogenetic intralayer and secant cracks stand out. They are common in all lithological varieties of Permian rocks that form the platform sedimentary cover - gypsum, limestone, marls, siltstones, mudstones and mudstone-like clays, sandstones, etc. Cracks perpendicular to the bedding plane predominate; inclined cracks (60–70°) are quite rare. The surface of straight, open and gaping cracks is smooth (in gypsum and limestone) and rough (in sandstone), very smooth, and in places as if polished (in argillite-like clays). On the walls there are deposits of iron and manganese hydroxides, deposits of calcite and gypsum.

The most fractured are mudstone-like clays and mudstones (crack density 0.1–0.3 m). In massive medium- and thick-layered limestones, cracks are located from each other at a distance of 0.5–2.5 to 5–9 m, and in thin-layered and foliated limestones - from 0.1 to 0.4 m, less often up to 1.5 m , in plaster - from 0.5 to 2.0 m or more. The density of cracks in sandstones depends on the composition and type of their cement. Sandstones that are weakly cemented and of medium density with clayey cement of the basal type are fractured more intensively than strong varieties of sandstones with carbonate cement.

The maximum width of intralayer and cross-cutting cracks is found in massive, pure limestones and strong sandstones (1–20, sometimes up to 50 cm). In thin-layered clayey limestones and marls, the width of cracks is from 0.2 to 3 cm.

In Kungur gypsum, despite its massiveness, the width of intralayer and secant cracks is small (up to 1–1.5 cm), which is associated with the high plasticity of the rocks. At the same time, the cracks in them serve as the initial cause of the development of the karst process along them, causing a sharp increase in water permeability (up to 100 m/day). In the valley zones, karst rocks are also complicated by unloading cracks.

In the Permian deposits of the Southern Cis-Urals, two predominant directions of intralayer and cutting cracks, oriented at right angles to each other and the bedding plane, have been identified. These directions are: on the Bugulma-Belebeevskaya Upland - NW 320–340° and NE 40–60° or NW 290–300° and NE 25–30° (Fig.6a), in the Kama-Belsky depression - NW 290–335° and NE 45–70°, on the Ufa plateau (Fig.6b) - NW 320–340° and NE 40–60° or NW 270–280°, in the Yuryuzan-Ai depression (Yangan-Tau region) - NW 310–320° and NE 40–55° or NW 270–290° and NE 15–25°, in the southern part of the Belsk depression - NW 340–350° and NE 60–70°. The northwestern direction accounts for 40–52%. of the total number of measured cracks, and the share of northeastern cracks is up to 35%.

Rice. 6. Rose diagrams of the directions of intralayer and secant cracks in the Permian deposits of the Southern Cis-Urals (in %)

a - Bugulma-Belebeevskaya Upland; b - Ufa plateau

The leading role of tectonic processes in the formation of rock fracturing on platform structures is established and recognized by many researchers. The actual material on the fracturing of the Upper Permian deposits of the Bugulma-Belebeevskaya Upland and the Lower Permian rocks of the Ufa Plateau and Pribelskaya Plain indicates agreement between the maxima of fracturing and the elements of rock occurrence.

The location of the hydrographic network of the territory under consideration is also consistent with the prevailing directions of fracturing. Intense karstification of carbonate deposits is also confined to linear zones of tectonic fracturing.

A type of lithogenetic cracks aredrying cracks. They are formed in subaerial conditions with the participation of weathering agents, are open at the surface and quickly narrow with depth. The smaller the layer thickness, the greater the number of such cracks. Drying cracks can be traced to a depth of 2.5–3 m from the surface, their width ranges from 1–2, rarely 2.5–3 cm in the upper part of the section to 1–2 mm in the lower part. The cracks are either open or filled with loose humus material.

Lithogenetic bedding fracturesclearly expressed in limestones and sandstones, with the greatest density (0.03–0.1 m) and the smallest openness (0.1–0.3 cm) characteristic of thin-layered limestones. The cracks in them are usually filled with clayey material. In medium- and thick-platy limestones, the density of cracks is 0.5–0.8 m, and the width is 0.5–2.0 cm. In sandstones, the density of bedding cracks varies from 0.05 to 0.3 m, and the width - from 0 .05–0.1 to 1–3 cm. Almost all cracks have loose sandy-clayey filler.

Unloading cracks(side and bottom pressure) are developed in river valleys. Their formation is associated with decompression of rocks caused by the release of geostatic pressure under the influence of erosion. The thickness of the unloading zone in the river valleys of the East European and Siberian platforms, according to literature data, is a few tens of meters. In sedimentary rocks, the depth of distribution of decompacted rocks depends on their strength and varies from 30 to 50 m.

Unloading cracks were studied in most detail by A.G. Lykoshin in the river valley.Ufa during surveys for the Pavlovsk hydroelectric power station. In the adit, he noted cracks ranging from 3 to 25 cm wide, in some places filled with clayey material. With depth, the number of cracks and their width decrease sharply. In the river valley Belaya in the Ufa region, cracks in the side wall break the gypsum into separate blocks parallel to the slope.

Unloading cracks in the areas of the Bugulma-Belebeevskaya Upland, Kama-Belsky and Yuryuzano-Aisky depressions have practically not been visually studied. However, it should be noted that in the river valleys of the Southern Cis-Urals, under conditions of interstratal downward flows of water, side pressure cracks, crossing both water-permeable and water-resistant rocks on the slopes, contribute to the drainage of aquifers to the river level. This explains the low flow rates of the sources, their small number, as well as the weakly expressed number of storeys on the steep slopes of the valleys of Belaya, Ika, Ufa, Yuryuzan, Aya, Chermasan, Useni, Dema, etc. Wells located in the edge parts of valleys and not reaching the river level often turn out to be low in water or even anhydrous.

The presence of cracks in the side wall, isolating the massif with hot gases from the aquifers of the Yuryuzan-Ai watershed, also explains the Yangantau “phenomenon” (gas thermal phenomena) of Bashkortostan.

Extensive material from hydrogeological surveys and water prospecting work in this territory indicates that the water permeability of dense rocks, which, as is known, depends on their fracturing, is significantly (on average 10 times) higher in river valleys than in watersheds. For example, in the valleys of the rivers Syun, Baza, Chermasan and others, the filtration coefficients of aquiferous Ufa sandstones range from 1–5 to 10–15 m/day, sometimes more, while at watersheds they do not exceed tenths of m/day.

A similar dependence of water permeability on orographic conditions is also observed for clayey rocks. This pattern, apparently, is of a general nature and indicates the presence of weakened zones under river valleys with increased water permeability of rocks, and therefore higher fracturing, in the formation of which the unloading factor undoubtedly plays a significant role.

The fracturing of rocks in the folded mountain region of Bashkortostan was studied by a number of researchers (Yu.E. Zhurenko, I.K. Zinyakhina, A.P. Rozhdestvensky, V.A. Romanov, G.S. Senchenko, R.A. Fatkullin, etc.) . They indicate the predominant development of fracturing of tectonic and lithogenetic types in this region.

Rock fracturing is found in almost any rock, regardless of structural position, petrographic composition, age, forming a complex system (network) of small and larger cracks that cut through the rock mass to a significant depth (up to 300–400 m). The largest cracks, grouped into systems of certain directions, separate massive and dense sedimentary, igneous and metamorphic rocks into blocks - individual units of various shapes and sizes.

Among the fracturing systems that penetrate the rocks of the Southern Urals, there are some generally insignificant differences in the orientation of fracturing in rocks of different ages and petrographic (lithological) composition that are revealed by statistical processing of field measurements. So, according to R.A. Fatkullin, in the Precambrian rocks of the metamorphic complex of the Uraltau anticlinorium (shales, quartzites), cracks strike in azimuths of 20°, 50°, 280°, 320°, 340°, in the sandstones of the Zilair formation (D 3 fm – C 1 t) - 0°, 40°, 80°, 350°, in igneous rocks of Silurian and Devonian age of the Irendyk uplift - 0°, 20°, 40°, 80°, 350°, in Devonian igneous rocks of the Kizilo-Urtazym synclinorium - 30 °, 60°, 90°, 280–300°, 350°.

The main directions of the hydrographic network of the region coincide with the fracturing of rocks.

Rock solubility. This process plays a vital role in the formation of karst. The solubility of rocks varies greatly in the presence of other salts (Tables 6, 7, 8).

Table 6

Solubility in the presence (V. M. Levchenko, 1950)

G/l

2,085

2,25

3,14

4,35

7,48

6,96

6,64 ,% volume

0,00

0,03

0,30

10,00

100,00

III. Suffusion – mechanical removal of small particles from loose rocks and cracks by moving underground water.

Suffusion is the result of hydrodynamic pressure that filtered water exerts on the rock. Suffusion usually occurs in sandy rocks. The removal of particles begins when the pressure gradient reaches a critical value. Critical gradient according to E.A. Zamarin equals

γ is the density of sand, n is the porosity of sand in fractions of units.

Suffusion occurs under the foundations of hydraulic structures and canals and can lead to the destruction of structures.

Lecture 6. assessment of groundwater reserves

To develop and extract groundwater, it is necessary to know groundwater reserves (sometimes called resources). They consist of several types:

Centuries-old

Q century = F×H×µ, where F is the area of ​​distribution of the water horizon, km 2 ; H – thickness of the water horizon, m, µ – water yield.

Renewable natural resources (reserves).

Q WHO = MF, where M is the module of underground flow l/s×km 2 .

Operating reserves

Q ex = +0.7Q exc , where α is the extraction coefficient, the maximum permissible value of lowering the level of the water horizon (usually no more than half the thickness of the aquifer, α = 0.5), t is the specified operating time, years (usually calculated for 15, 25, 50 years).

To use groundwater you need to knowoperational resources. This is the volume of groundwater in m 3 /day, which can be obtained by technically and economically rational water intake structures under a given operating mode and water quality that meets the requirements throughout the entire estimated period of water consumption.

Operating reserves (resources) are provided by:

natural (centuries-old) capacitive reserves;

natural (renewable) resources;

attracted resources;

artificial reserves (formed during hydraulic engineering construction, irrigation, artificial replenishment).

Operating reserves are divided into 4 categories: A, B, C 1, C 2 . Categories A and B are industrial reserves.

Lecture 7. Groundwater regime

Under mode groundwater should be understood as changes in its level, temperature, chemical composition and flow in time and space under the influence of natural and artificial factors.

Under natural factors, influencing the regime of groundwater, understand the change in the conditions of recharge and discharge of groundwater depending on the regime of surface water, as well as on the amount of precipitation, temperature and air pressure. A number of researchers associate changes in groundwater regimes with solar activity.

Artificial factors, affecting the groundwater regime are associated with practical human activities. These include pumping, raising the water horizon in reservoirs, irrigation, drainage, etc.

It is necessary to distinguish between daily, seasonal, annual and long-term changes in the elements of the groundwater regime.

Daily level fluctuations have been studied most fully; they depend on the moisture deficit in the aeration zone and are on the order of 0.7-3.2.

Seasonal variations mainly depend on precipitation and ground temperature; The influence of these factors is clearly recorded in spring and autumn.

Annual fluctuations in groundwater levels depend on the amount of precipitation, its intensity, moisture deficit and soil temperature. The annual amplitudes of fluctuations are 0.78-3.05 m. According to 60-year observations, a number of maxima and minima are recorded, repeating every 10-13 years. The minimum water levels coincide with dry years, the maximum with wet years.

It is customary to distinguish between two types of groundwater regime: coastal and watershed.

In watershed areas, the groundwater regime depends mainly only on climatic factors; Fluctuations in surface water levels have little effect.

The groundwater regime in coastal river and sea areas or near reservoirs is in direct connection with the surface water regime; their influence affects distances reaching 5-11 km. The amplitude of groundwater level fluctuations in a well located 1 km from the river reaches 6.5 m.

The groundwater regime is influenced by tidal currents extending up to 15 km from the coast.

In areas with a humid climate, the amplitude of fluctuations in groundwater levels far from rivers usually does not exceed 1-1.5 m and rarely reaches 2-2.5 m. The greatest amplitude is observed in the spring during the snowmelt period, the smallest in winter. The productivity of aquifers, as well as the chemical composition and temperature of groundwater, change little throughout the year.

In mountainous areas, fluctuations in groundwater levels and changes in the productivity of aquifers throughout the year are very dramatic.

In arid areas, as in humid ones, the regime of groundwater depends on meteorological factors. The difference in the regime of these areas is that in arid areas the annual amplitude of groundwater level fluctuations reaches 6-8 m with a significant decrease in the productivity of the aquifer.

Under the influence of artificial factors, the regime of groundwater can change dramatically. This is most clearly manifested in areas of water intake and mining, where the decrease in groundwater levels per year is at least 1.5-2 m.

Changing the regime of groundwater, in particular fluctuations in its level, is of great practical importance: when the level rises, flooding of buildings or swamping of areas can occur, and in arid areas where groundwater lies at a shallow depth of 1.5 m, a rise in level can cause evaporation from the surface of groundwater and the accumulation of salts in the soil with the formation of solonetzes or solonchaks.

Lecture 8. Fundamentals of engineering geology

Plan:

The concept of engineering-geological properties of rocks.

Methods for studying the engineering-geological properties of rocks.

Basic engineering-geological properties of rocks.

Technical reclamation of rocks.

Rocks used as foundations for various structures are soils. Soils are rocks and soils that are studied as multicomponent systems that change over time, with the aim of understanding them as an object of human engineering activity. Due to differences in origin and geological development, rocks are not the same. Some properties may change during the operation of structures. Engineering-geological properties are influenced by geomorphological conditions, modern geological processes, hydrogeological conditions (groundwater depth, chemical composition), etc.

Engineering-geological properties of rocks are studied:

geological methods (age of rocks, origin, nature of occurrence, thickness) with drilling of wells and pits.

using field methods (stamps). They are based on the use of special installations that make it possible to evaluate the properties of rocks under the conditions of their natural occurrence (filling, pumping, etc.).

laboratory methods (granulometric composition, plasticity, natural humidity, porosity, degree of density, volumetric weight, soil diagram, etc.).

When studying rocks, their condition is studied (fractures, weathering, crack filler, compressive strength, etc.). The classification of the strength properties of rocks is given in Table. 9.

Table 9

Classification of rocks according to compressive strength 60-100

100-150

150-230

230-350

350-520

520-800

800-1200

1200-1800

1800-2700

>2700

The main engineering-geological properties of rocks include the following indicators:

1. The granulometric composition of non-cohesive (determined by sieve analysis) and cohesive rocks is determined by the hydrometric method - based on different settling rates of particles in water). The settling rate is determined by Stokes. The coefficient of heterogeneity and particle diameters, less than which a given rock contains 60 and 10% of particles, respectively. When K > 3, rocks are called heterogeneous.

2. Rock density - the ratio of the mass of solid particles to their volume (the density of sand rocks is usually 2.5-2.8 g/cm³).

3. Rock porosity - the ratio of the volume of all pores to the total volume of the rock: .

4. For sands and gravel, the angle of repose is determined. This is the angle formed by the surface of a sand cone with a horizontal plane when sand is freely poured onto the plane in an air-dry state.

5. Plasticity - the ability of a rock to change shape under the influence of external forces without destruction or rupture. Determined in the humidity range. The upper limit of plasticity is humidity, with an increase in which the rock loses its plastic properties.

Technical reclamation of rocks consists of regulating and transforming the state and properties of rocks in a given direction, changing the granulometric composition, the structure of the crystal lattice, and the degree of solidity. Certain methods of technical reclamation produce such profound and radical changes that they completely lose their natural properties. As a result of two-solution silicization, sands turn into monolithic rocks. Clay rocks turn to stone after firing, freezing, cementation.

Methods of rock reclamation: strengthening with granulometric additives, mechanical compaction (vibration compaction), rolling, seismic compaction, water reduction, etc.

Literature

Main

Vsevolozhsky V.A. Fundamentals of hydrogeology: Textbook. - 2nd ed. M: Moscow State University Publishing House, 2007. 448 p.

Bogomolov G.V. Hydrogeology with basics of engineering geology. M.: Publishing house "Higher School", 1966. 316 p.

Additional

Abdrakhmanov R.F. Hydrogeoecology of Bashkortostan. Ufa: Informreklama, 2005. 344 p.

Abdrakhmanov R.F. Methodological instructions for performing practical exercises in the course “Hydrogeology”. Ufa, IG UC RAS, 2008. 44 p.

Abdrakhmanov R.F., Martin V.I., Popov V.G. and others. Karst of Bashkortostan. Ufa: Informreklama, 2002. 383 p.

Abdrakhmanov R.F., Chalov Yu.N., Abdrakhmanova E.R. Fresh underground waters of Bashkortostan. Ufa: Informreklama, 2007. 184 p. pdf The book summarizes the results of research in the field of using geothermal methods to solve theoretical and applied problems...

Strokova L.A. (comp.) Engineering structures

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• added 03/12/2011

Tutorial. – Tomsk: Publishing house. TPU, 1999. – 114 p.

The textbook is devoted to the consideration of various types of engineering structures (civil and industrial, hydraulic, linear).
The manual was prepared at the Department of Hydrogeology and Engineering Geology of Tomsk Polytechnic University and is intended for students...

Topic: Hydrogeology as a science. Water in nature.

1. Hydrogeology. Stages of development of hydrogeology.

Let us recall the definition of the science of hydrogeology. Hydrogeology- the science of groundwater, studying its origin, conditions of occurrence and distribution, laws of movement, interaction with water-bearing rocks, formation of chemical composition, etc.

Let us briefly consider the history of the development of this science.

1.1 Stages of development of hydrogeology

In the history of groundwater studies in the USSR, there are 2 periods:

1) pre-revolutionary;

2) post-revolutionary.

In the pre-revolutionary period, three stages in the study of groundwater can be distinguished:

1. accumulation of experience in the use of groundwater (X - XVII centuries)

2. the first scientific generalized information about groundwater (XVII - mid-XIX centuries)

3. establishment of hydrogeology as a science (second half of the 19th century and beginning of the 20th century)

In 1914, the first department of hydrogeology in Russia was organized at the engineering faculty of the Moscow Agricultural Institute (now the Moscow Irrigation Institute).

The post-revolutionary period can be divided into 2 stages:

1. pre-war (1917-1941)

2. post-war

To train hydrogeological engineers, a hydrogeological specialty was established at the Moscow Mining Academy in 1920: a little later it was introduced at other institutes and universities. The most prominent hydrogeologists F.P. began teaching at the institutes. Savarensky, N.F. Pogrebov, A.N. Semikhatov, B.C. Ilyin et al.

By the beginning of the first five-year plan (1928), as well as during subsequent five-year plans, hydrogeological research was carried out in the Donbass, Eastern Transcaucasia, Central Asia, Northern Ukraine, Kazakhstan, Turkmenistan and many other regions of the country.

The First All-Union Hydrogeological Congress, held in 1931, was of great importance for the further development of hydrogeology. in Leningrad.

In the 1930s, summary maps (hydrogeological, mineral water, hydrogeological zoning) were compiled for the first time, which were of great importance for planning further hydrogeological research. At the same time, under the editorship of N.I. Tolstikhin, volumes “Hydrogeology of the USSR” began to be published. Before the Great Patriotic War, 12 issues of this multi-volume work were published.

The post-war stage is characterized by the accumulation of materials in deep-lying waters.

For a more in-depth scientific analysis and broad regional generalization of materials on groundwater, it was decided to prepare for publication 45 volumes of “Hydrogeology of the USSR”, and in addition, compile 5 consolidated volumes.

2. Water in nature. The water cycle in nature.

On the globe, water is found in the atmosphere, on the surface of the earth and in the earth's crust. In the atmosphere water is found in its lower layer - the troposphere - in various states:

1. vapor;

2. droplet liquid;

3. hard.

Superficial water is in liquid and solid state. In the earth's crust water is found in vapor, liquid, solid, and also in the form of hygroscopic and film water. Together, surface and groundwater make up the water shell - hydrosphere.

The underground hydrosphere is limited from above by the surface of the earth; its lower boundary has not been reliably studied.

There are large, internal and small gyres. During a large cycle, moisture evaporates from the surface of the oceans, is transported in the form of water vapor by air currents to land, falls here on the surface in the form of precipitation, and then returns to the seas and oceans by surface and underground runoff.

With a small circulation, moisture evaporates from the surfaces of oceans and seas. It also falls here in the form of precipitation.

The process of the cycle in nature in quantitative terms is characterized water balance, the equation of which the share of a closed river basin has the form for a long-term period:

X = y+Z-W (according to Velikanov),

where x is precipitation per catchment area, mm

y - river flow, mm

Z - evaporation minus condensation, mm

W is the average long-term recharge of deep aquifers due to precipitation or the flow of groundwater to the surface within the river basin.

The internal circulation is provided by that part of the water that evaporates within the continents - from the water surface of rivers and lakes, from land and vegetation, and falls there in the form of precipitation.

3. Types of water in minerals and rocks.

One of the earliest classifications of water types in race rocks was proposed in 1936 by A.F. Lebedev. In subsequent years, a number of other classifications were proposed. Based on Lebedev’s classification, most scientists distinguish the following types of water:

1. Steamy water

Found in the form of water vapor in the air, present in the pores and cracks of rocks and in the soil, it moves along with air currents. Under certain conditions, it can transform into liquid form through condensation.

Vaporous water is the only type that can move in pores with little moisture.

2. Bound water

Present mainly in clayey rocks, it is held on the surface of particles by forces significantly exceeding the force of gravity.

A distinction is made between tightly bound and loosely bound water.

A) strongly bound water(hydroscopic) it is in the form of molecules in an absorbed state, held on the surface of particles by molecular and electrostatic forces. It has high density, viscosity and elasticity, is characteristic of finely dispersed rocks, is not capable of dissolving salts, and is not accessible to plants.

b) loosely knit(film) is located above tightly bound water, is held by molecular forces, is more mobile, the density is close to the density of free water, is able to move from particles to particles under the influence of sorption forces, the ability to dissolve salts is reduced.

3. Capillary water

It is located in the capillary pores of rocks, where it is held and moved under the influence of capillary (meniscus) forces acting at the boundary of water and air located in the pores. It is divided into 3 types:

A) actual capillary water is located in the pores in the form of moisture from the capillary floodplain above the groundwater level. The thickness of the capillary floodplain depends on the granulometric composition. It varies from zero in pebbles to 4-5 m in clayey rocks. Capillary water itself is available to plants.

b) suspended capillary water is located predominantly in the upper horizon of the rock or in the soil and is not in direct connection with the groundwater level. When the moisture content of the rock increases above the minimum moisture capacity, water flows into the underlying layers. This water is available to plants.

V) pore corner water is held by capillary forces in the pores of sand and clay rocks at the points of contact of their particles. This water is not used by plants; when humidity increases, it can turn into suspended water or into capillary water itself.

4. Gravity water

Submits to gravity. The movement of water occurs under the influence of this force and transmits hydrostatic pressure. It is divided into 2 types:

A) seeping- free gravitational water in a state of downward movement in the form of separate streams in the aeration zone. The movement of water occurs under the influence of gravity.

b) aquifer moisture, which saturates the aquifers to PV. Moisture is retained due to the waterproofness of the waterproof layer (further discussion refers to the topic “Gravitational water”).

5. Water of crystallization

It is part of the crystal lattice of a mineral, such as gypsum (CaS0 4 2H 2 O), and retains its molecular shape.

6. Solid water in the form of ice

In addition to the above six species, there are chemically bound water, which participates in the structure of the crystal lattice of minerals in the form of H +, OH ions,” i.e., does not retain its molecular form.

4. The concept of porosity and porosity.

One of the most important hydrogeological indicators of rocks is their porosity. In sandy rocks there are steam porosity, and in strong ones - cracked.

Groundwater fills pores and cracks in rocks. The volume of all voids in rock is called duty cycle. Naturally, the greater the porosity, the more water the rock can hold.

The size of voids is of great importance for the movement of groundwater in rocks. In small pores and cracks, the area of ​​contact of water with the walls of the voids is greater. These walls provide significant resistance to the movement of water, so its movement in fine sand, even with significant pressure, is difficult.

The porosity of rocks is distinguished: capillary(porosity) and non-capillary.

To capillary duty cycle include small voids where water moves mainly under the influence of surface tension and electrical forces.

To non-capillary duty cycle include large voids devoid of capillary properties, in which water moves only under the influence of gravity and pressure difference.

Small voids in rocks are called porosity.

There are 3 types of porosity:

2. open

3. dynamic

Total porosity is quantitatively determined by the ratio of the volume of all small voids (including those not communicating with each other) to the entire volume of the sample. Expressed in fractions of a unit or as a percentage.

Or

where V n is the volume of pores in the rock sample

V – sample volume

Total porosity is characterized by the porosity coefficient e.

Porosity coefficient e is expressed by the ratio of the volume of all pores in the rock to the volume of the solid part of the rock (skeleton) V c, expressed in fractions of unity.

This coefficient is widely used especially in research

clay soils. This is due to the fact that clay soils swell when moistened. Therefore, it is preferable to express clay porosity through e.

The porosity ratio can be expressed as follows

, dividing the numerator and denominator by V c we get

The value of total porosity is always less than 1 (100%), and the value e may be equal to 1 or greater than 1. For plastic clays e ranges from 0.4 to 16.

Porosity depends on the nature of the composition of particles (grains).

Non-capillary porosity includes large pores in coarse clastic rocks, cracks, channels, caves and other large voids. Cracks and pores can communicate with each other or be torn.

Open porosity characterized by the ratio of the volume of interconnected open pores to the entire volume of the sample.

For granular, unconsolidated rocks, the open porosity is close in value to the total.

Dynamic porosity is expressed as the ratio to the entire sample volume of only that part of the pore volume through which liquid (water) can move.

Studies have shown that water does not move throughout the entire volume of open pores. Part of the open pores (especially at the junction of particles) is often occupied by a thin film of water, which is firmly held by capillary and molecular forces and does not participate in movement.

Dynamic porosity, unlike open porosity, does not take into account the volume of pores occupied by capillary-bound water. Typically, dynamic porosity is less than open porosity.

Thus, the fundamental difference between the characterized types of porosity lies (quantitatively) in the fact that in cemented rocks the total porosity is more open, and the open porosity is more dynamic.

Control questions:

1. What does the science of hydrogeology study?

2. How does the water cycle work in nature?

3. Name the types of water found in minerals and rocks.

4. What is porosity? What are its types? How is porosity determined?

5. What do I mean by duty cycle? Name and describe its types.

Hydrogeology (from Greek. kshog- water and geology- Earth science) is the science of groundwater, studying its composition and properties, origin, patterns of distribution and movement, as well as interaction with rocks. Hydrogeology is closely related to hydrology, geology (including engineering geology), meteorology, geochemistry, geophysics and other earth sciences. It relies on data from mathematics, physics, and chemistry and makes extensive use of their research methods.

Historical reference. The accumulation of practical knowledge about groundwater, which began in ancient times, accelerated with the advent of cities and irrigated agriculture. The art of constructing dug wells several tens of meters deep was known 2-3 thousand years BC. e. in Egypt, Central Asia, India, China and other countries. There is information about treatment with mineral waters during the same period.

In the 1st millennium BC. e. the beginnings of scientific ideas about the properties of natural waters, their origin, conditions of accumulation and water cycle on Earth appeared (in Ancient Greece - Thales (VII-VI centuries BC), Aristotle (IV centuries BC); in Ancient Rome - Lucretius, Vitruvius (1st century BC), etc.).

The study of groundwater was facilitated by the expansion of work related to water supply, the construction of capture structures (for example, kariz among the peoples of the Caucasus and Central Asia), and the extraction of salt water for evaporation of salt by digging wells and then drilling (territory of Russia, XII-XVII centuries). The concepts of non-pressure, pressure (rising from the bottom up) and self-flowing waters arose. The latter received in the 12th century. name artesian (from the province of Artois in France). During the Renaissance and later, the works of Western European scientists Agricola, Palissy, Steno and others were devoted to groundwater and its role in natural processes. In Russia, the first scientific ideas about groundwater as natural solutions, their formation through the infiltration of atmospheric precipitation and the geological activity of groundwater were expressed by M. V. Lomonosov in his essay “On the Layers of the Earth” (1763). At the end of the 19th - beginning of the 20th centuries. patterns of distribution of groundwater were identified (V.V. Dokuchaev, P.V. Ototsky) and a map of groundwater zonation in the European part of Russia was compiled. Until the middle of the 19th century. The study of groundwater developed as an integral part of geology. Then it is isolated into a separate discipline, which subsequently becomes more and more differentiated. In the formation of hydrogeology, a major role was played by French engineers L. Darcy, J. Dupuis, Chezy, German scientists E. Prinz, K. Keilhack, H. Hoefer and others, US scientists A. Hazen, C. Slichter, O. Meinzer, A. Lane and others, Russian geologists S.P. Nikitin, I.V. Mushketov, etc. Systematic geological surveying carried out by the Geological Committee played a major role in the development of hydrogeology in Russia. Subsequently, hydrogeological research became widespread. The study of groundwater became systematic, a network of hydrogeological institutions was created, and training of hydrogeological specialists was organized. The industrialization of the country gave impetus to the development of hydrogeological research for centralized water supply to new cities, large plants and factories. Over the following years, hydrogeology has developed into a multifaceted field of geological knowledge, in which numerous branches began to develop:

• - general hydrogeology;
• - groundwater dynamics;
• - the doctrine of the regime and balance of groundwater;
• - hydrogeochemistry;
• - the doctrine of mineral, industrial and thermal waters;
• - the doctrine of search and exploration of groundwater;
• - reclamation hydrogeology;
• - hydrogeology of mineral deposits;
• - regional hydrogeology.

General hydrogeology studies the origin of groundwater, its physical and chemical properties, and interaction with host rocks. Creative contributions to this area of ​​hydrogeology were made by Soviet scientists A. F. Lebedev, A. N. Buneev, V. I. Vernadsky and others, the Austrian geologist E. Suess, the US scientist A. Lane, the German hydrogeologist X. Höfer and others. The study of groundwater in connection with the history of tectonic movements, processes of sedimentation and diagenesis made it possible to clarify the history of their formation and contributed to the appearance in the 30-40s. XX century new branch of general hydrogeology - paleohydrogeology(the study of underground waters of past geological eras).

Hydrogeochemistry studies the processes of formation of the chemical composition of groundwater and the patterns of migration of chemical elements in it. Theoretical premises are based on modern ideas about the structure of natural waters, the prevalence of chemical elements in the earth’s crust and rocks, the concept of clarks, factors of migration, accumulation, sedimentation and dispersion of various elements and their isotopes in natural waters, the gas composition of groundwater and other characteristics. The foundations of hydrogeochemistry were laid by the works of V.I. Vernadsky in the 30s. XX century This industry finally took shape in the 40s. XX century

Groundwater dynamics is a branch of hydrogeology that considers the theoretical foundations and methods of studying the quantitative patterns of the regime and balance of groundwater. From the point of view of methodological constructions based on the theory of filtration, this branch is inextricably linked with hydraulics and hydromechanics. In foreign literature, the concept of groundwater dynamics is often absent; most of the issues related to it are considered by groundwater hydrology.

A major role in the development of the theory of groundwater dynamics was played in our country by N. E. Zhukovsky, N. N. Pavlovsky, G. N. Kamensky and others, and abroad by J. Dupuis and L. Darcy (France), A. Till (Germany), F. Forchheimer (Austria), C. Slichter, C. Hayes, M. Masket, R. de Uist (USA).

Many principles of groundwater dynamics, relating mainly to hydromechanical problems, were laid down in the second half of the 19th - early 20th centuries. researchers working in the field of hydraulics and theoretical mechanics - French scientists D. Darcy and J. Dupuis, who established the linear law of filtration, Russian scientist N. E. Zhukovsky, who worked on the theory of groundwater movement, etc. Modern foundations of the theory and practice of underground dynamics waters were laid down mainly by Soviet scientists who carried out research in the 20-30s. XX century research on solving problems of hydraulic engineering. N. N. Pavlovsky identified problems of groundwater dynamics in connection with hydraulic engineering construction, G. N. Kamensky studied the problems of connecting groundwater dynamics with geological conditions, issues of groundwater movement in heterogeneous layers, developed a method for calculating groundwater backwaters, etc. For In the development of groundwater dynamics, the study of issues of underground petroleum hydraulics (gas-hydrodynamics), begun in our country by L. S. Leibenzon, is of great importance.

In the modern period:

• - characterized by the active use of hydrodynamic calculations and forecasting based on them in almost all hydrogeological studies;
• - the development of a methodology for calculating stationary filtration has been completed and the theoretical basis for forecasting groundwater backwater in areas of hydraulic structures and irrigated areas has been developed;
• - methods for assessing operational groundwater reserves are substantiated;
• - the main directions of research into the regional dynamics of deep and interacting aquifers are formulated.

The impact of human economic activity on groundwater leads to the need to consider complex calculation schemes, therefore, in addition to analytical calculation methods, methods of mathematical modeling on a computer are widely used. This allows hydrogeological calculations to be carried out with the fullest possible account of the natural situation and all operating factors.

Along with the solution of direct hydrogeodynamic problems, in which a forecast of the regime and balance of groundwater is given, in the dynamics of groundwater, solutions to inverse problems are considered - restoration of the parameters of the filtration scheme based on data on the regime of groundwater (for example, during long-term operation of large groundwater intakes, in areas of reservoirs , quarries). A new direction that studies the physico-chemical processes that occur during the interaction of groundwater with the host rocks is becoming important for the study of groundwater pollution and the substantiation of hydrogeochemical methods for searching for minerals.

In the middle of the 20th century. stood out as an independent direction radiohydrogeology- study of migration of radioactive elements in groundwater (works by A.P. Vinogradov, A.V. Shcherbakov).

The doctrine of mineral, industrial and thermal waters.

The study of mineral waters examines the issues of the chemical composition and origin of mineral waters, their classification into main genetic types, creates an idea of ​​the deposits and resources of mineral waters and solves the problems of their practical use (mainly for resort and sanatorium treatment). Waters with a high content of various elements (iodine, bromine, boron, strontium, lithium, radium, etc.), called industrial, are studied to extract the specified elements from them. The study, search and exploration of deposits of thermal and superheated waters are carried out in order to use them for district heating of cities and towns.

The study of search and exploration of groundwater is associated with the development of methods for identifying deposits of groundwater suitable for organizing water supply, irrigation and other practical purposes; their quantitative and qualitative assessment; solving problems arising during the construction of engineering structures, drainage and irrigation. The methodology for hydrogeological research was developed in connection with the search and exploration of groundwater.

Reclamation hydrogeology develops methods for improving the hydrogeological conditions of irrigated and drained territories for the purpose of their most rational agricultural development. Issues of reclamation hydrogeology (determining irrigation norms, providing water to agricultural crops, forecasting the groundwater regime, combating soil salinization, etc.) are important for the vast territory of the arid zone of the globe.

Hydrogeology of mineral deposits deals with the study of groundwater in relation to the tasks of geological and industrial assessment of deposits, their development and development. Two directions are being developed: hydrogeology of solid mineral deposits And hydrogeology of oil and gas fields, which is explained by the specifics of exploration, development and production of these minerals. Stands out mine hydrogeology, developing measures to combat groundwater.

Regional hydrogeology studies the patterns of distribution of groundwater in various natural conditions in connection with geological structures. It is developed on the basis of hydrogeological mapping of various scales - from 1:500,000 to 1:10,000, based on geological surveys. Along with maps of individual regions, consolidated hydrogeological maps of the territory of our country are compiled. As a result of regional studies, numerous general and special maps are created (Fig. 43, 44). On the basis of regional hydrogeology, the doctrine of horizontal and vertical zoning was developed.

Rice. 43.

Groundwater is water found in the rock strata of the upper part of the earth's crust in liquid, solid and vapor states. Depending on the nature of the voids of the water-bearing rocks, groundwater is divided into pore water - in sands, pebbles and other clastic rocks, fissure (vein) - in rocks (granites, sandstones) and karst (fissure-karst) - in soluble rocks (limestones, dolomites , plaster, etc.).

Groundwater that moves under the influence of gravity is called gravitational, or free, in contrast to waters bound and held by molecular forces - hygroscopic, film, capillary And crystallization. Layers of rocks saturated with gravitational water form aquifers, or strata. Groundwater has varying degrees of permeability and yield (the ability to flow out of aquifers under the influence of gravity). The first permanently existing unconfined aquifer from the Earth's surface is called groundwater horizon. Directly above their surface - groundwater table- capillary waters are common, which can be suspended, that is, not communicating with him. The entire space from the surface of the Earth to the groundwater table is called aeration zone, in which it takes place

22 21 20 19 18 17 16 15 14 13 12 1 1 Yu 9 8 7 6 5 4 3 2

2 4 6 8 10 12 14 16 18

Rice. 44. Map of the depth of the groundwater surface, constructed using GIS technology.

seepage of water from the surface. In this zone, temporary accumulations of groundwater are formed, which are called high water. Aquifers lying below groundwater are separated from them by layers of waterproof ( waterproof) or low-permeability rocks and are called horizons of interstratal waters. They are usually under hydrostatic pressure (artesian waters), less often they have a free surface and are free of pressure (free-flowing waters). The area of ​​recharge of interstratal waters is located in places where water-bearing rocks reach the surface (or in places where they are shallow); recharge also occurs through the flow of water from other aquifers.

Groundwater is a natural solution containing over 60 chemical elements (in the largest quantities - K, N3, Ca, IU, Fe, Al, Cl, 8, C, 81, Li, O, H), as well as microorganisms (oxidizing and reducing various substances). As a rule, groundwater is saturated with gases (CCb, Cb, N2, C2H2, etc.). According to the degree of mineralization, groundwater is divided (according to V.I. Vernadsky) into fresh (up to 1 g/l), brackish (from 1 to 10 g/l), saline (from 10 to 50 g/l) and underground brines (over 50 g/l). In later classifications, underground brines include waters with a mineralization of more than 36 g/l. According to temperature data, they distinguish between supercooled (below 0 °C), very cold (from 0 to -4 °C), cold (from -4 to -20 °C), warm (from 4 to 37 °C), hot (from 37 up to 50 ° C), very hot (from 50 to 100 ° C) and overheated (over 100 ° C) groundwater.

Based on their origin, there are several types of groundwater.

Infiltration waters are formed due to the seepage of rain, melt and river waters from the Earth's surface. In composition they are predominantly hydrocarbonate-calcium And magnesium When gypsum-bearing rocks are leached, calcium sulfate, and during the dissolution of salt-bearing minerals - sodium chloride waters.

Condensation groundwater is formed as a result of the condensation of water vapor in the pores or cracks of rocks.

Sedimentation waters are formed in the process of geological sedimentation and usually represent modified buried waters of marine origin - sodium chloride, calcium-sodium chloride, etc. These also include buried brines of salt basins, as well as ultra-fresh waters of sand lenses in moraine deposits. Waters formed from magma during its crystallization and during metamorphism of rocks are called magmatogenic, or juvenile(according to the terminology of E. Suess).

One of the indicators of the natural conditions for the formation of groundwater is the composition of gases dissolved in them and freely released. The upper aquifers with an oxidizing environment are characterized by the presence of oxygen and nitrogen; the lower parts of the section, where a reducing environment predominates, gases of biochemical origin (hydrogen sulfide, methane) are typical. In tectonically active areas, waters saturated with carbon dioxide are common (carbon dioxide waters of the Caucasus, Pamirs, Transbaikalia). Perhaps the saturation of waters with carbon dioxide is associated with thermometamorphism, which releases CO2. Near the craters of volcanoes there are acidic sulfate waters (so-called fumarolic baths).

In many water-pressure systems, which are often large artesian basins, three zones are distinguished, differing in the intensity of water exchange with surface waters and the composition of groundwater. The upper and marginal parts of the basins are usually occupied by infiltrating fresh waters. There are zones of active water exchange (according to N.K. Ignatovich), or active circulation. In the central deep parts of the basins there is a zone of very slow water exchange, or stagnation, where highly mineralized waters are common. In the intermediate zone of relatively slow or difficult water exchange, mixed waters of various compositions are developed.

The distribution patterns of groundwater depend on many geological and physical-geographical factors. Artesian basins and slopes are developed within platforms and marginal troughs (for example, the West Siberian, Moscow and Baltic artesian basins). On the platforms there are large areas with a highly elevated Precambrian crystalline foundation, characterized by the development of fissure waters (Ukrainian crystalline massif, Anabar massif, etc.), in folded mountain areas - fissure-type groundwater.

Peculiar hydrogeological conditions that determine the nature of circulation and the composition of groundwater are created in areas of development of permafrost rocks, where supra-permafrost, inter-permafrost and sub-permafrost waters are formed.

Groundwater is part of the Earth's water resources. The total reserves of groundwater on land are over 60 million km3. They are considered as a mineral resource. Unlike other types of minerals, groundwater reserves are renewable during exploitation. Areas of aquifers or their complexes, within which there are conditions for the selection of groundwater of a certain composition that meets established standards, in quantities sufficient for their economically feasible use, are called groundwater deposits.

Based on the nature of their use, groundwater is divided in Russia into household, drinking, technical, industrial, mineral waters And thermal waters. Groundwater of the domestic and drinking type includes fresh water that meets the conditions (with certain taste qualities and does not contain substances and microorganisms harmful to human health). Industrial waters with a high content of individual chemical elements (I, Br, B, 1L, etc.) are of interest to various industries. Groundwater containing specific components (gases, microcomponents) is used for medicinal purposes and as table drinks.

In some cases, groundwater causes swamping and flooding of territories, landslides, subsidence of soil under engineering structures, and complicates mining operations and mining operations in mines and quarries. To reduce the influx of groundwater into the area of ​​industrial facilities, they use drainage, drainage And drainage of deposits.

Many qualitative and quantitative indicators of groundwater parameters (level, pressure, flow, chemical And gas compositions, temperatures etc.) are subject to short-term, seasonal, long-term and secular changes that determine the regime of groundwater. The latter reflects the process of formation of groundwater in time and within a certain space under the influence of various natural regime-forming factors: climatic, hydrological, geological, hydrogeological and factors created as a result of human activity.

The greatest fluctuations in regime elements are observed in shallow groundwater.

In Russia, forecasts of the groundwater regime for the pre-spring minimum, maximum and autumn water levels in the zone of intensive water exchange are compiled annually. Forecasts are issued in the form of maps that show changes in groundwater levels.

Sources of groundwater - springs, springs and natural outlets of groundwater on the earth's surface (on land or under water). The formation of sources can be caused by various factors: the intersection of aquifers with negative forms of modern relief (for example, river valleys, ravines, ravines and lake basins), geological and structural features of the area (the presence of cracks, zones of tectonic disturbances, contacts of igneous and sedimentary rocks), filtration heterogeneity of water-bearing rocks, etc.

In particular, on the territory of the city of Penza and its environs, several actively living neotectonic zones were found, identified by the authors (Klimov, Klimova, 1997, 2006). These zones are developed in areas of relief bends and are traced by spring outlets along the entire length of the fault. The length of these discontinuous structures ranges from several meters to 15 km. The latter structure is stretched along the Bezymyanny stream in the north of Penza and is visible on the satellite image from infiltration evaporation from the soil. The maximum flow rate of springs in Penza is 4 l/s (Samovarnik spring). The depth of occurrence of near-surface faults is no more than 50 m, less often - deeper, for example, along the bed of the Staraya Sura River, as indicated by the presence of mineralized waters in Akhuny, lifted by a well from a depth of several hundred meters.

There are several classifications of sources. According to the classification of the domestic hydrogeologist A. M. Ovchinnikov, three groups of sources are distinguished according to the type of groundwater supply.

• 1. Springs fed by perched waters are usually located in the aeration zone and have sharp fluctuations in flow rate (up to complete disappearance in the dry season), chemical composition and water temperature.
• 2. Sources fed by groundwater are characterized by great constancy over time, but are also subject to seasonal fluctuations in flow rate, composition and temperature; they are divided into erosional (appearing as a result of deepening of the river network and opening of aquifers), contact (associated with contacts of rocks of different permeability) and overflow (usually ascending, associated with facies variability of layers or tectonic disturbances).
• 3. Sources of artesian waters are distinguished by the greatest constancy of the regime; they are located in discharge areas of artesian basins.

According to the mode features, all sources can be divided into constantly, seasonally And rhythmically acting. Studying the regime of sources is of great practical importance when using them for drinking and medicinal water supply.

According to hydrodynamic characteristics, springs are divided into two types: descending, fed by free-flow waters, and ascending, fed by pressure (artesian) waters.

Sources associated with porous rocks are distributed more or less evenly in places where the aquifer reaches the surface. Springs in fractured rocks are located at the intersection of fractures with the Earth's surface. The sources of karst areas are characterized by significant fluctuations in the regime associated with the amount of precipitation.

The temperature of the water in the sources depends on the depth of the groundwater, the nature of the supply channels, the geographical and hypsometric position of the source and the temperature regime of the substrate in which the groundwater is contained. In the area of ​​development of permafrost rocks, there are springs with a temperature of about 0 °C. In areas of young volcanism, hot springs are common, often with a pulsating regime.

The chemical and gas composition of spring water is very diverse; it is determined mainly by the composition of the discharged groundwater and the general hydrogeological conditions of the area. Registration of the natural outlet of water from various sources is called their capture.

Water permeability of rocks is the ability of rocks to pass water. The degree of water permeability depends on the size and number of interconnected pores and cracks, as well as on the location of rock grains. Well-permeable rocks include pebbles, gravel, coarse sands, intensely karst and fractured rocks. Almost impermeable (waterproof) rocks are clays, dense loams, non-fractured crystalline, metamorphic and dense sedimentary rocks.

The water permeability of rocks can be determined by the filtration rate equal to the amount of water flowing through a unit cross-sectional area of ​​the filter rock. This dependence is expressed by the Darcy formula:

where V is the filtration speed; To- filtration coefficient; / -pressure gradient equal to the pressure drop ratio N to the filtration path length b

I = Иь.

The filtration coefficient has the dimension of speed (cm/s, m/day). Thus, the filtration rate with a pressure gradient equal to unity is identical to the filtration coefficient.

Due to the fact that water in rocks can move under the influence of various reasons (hydraulic pressure, gravity, capillary, adsorption, capillary-osmotic forces, temperature gradient, etc.), the quantitative characteristics of the water permeability of rocks can be expressed not only by the filtration coefficient, but also coefficients water conductivity And piezoelectric conductivity. In hydrogeological studies and calculations, the water conductivity coefficient (the product of the filtration coefficient and the thickness of the aquifer) is an indicator of the filtration capacity of the rock.

Depending on the geological structure, aquifers in filtration terms can be isotropic, when water conductivity is the same in any direction, and anisotropic, characterized by a natural change in water permeability in different directions.

The study of the water permeability of rocks is necessary when searching and exploring groundwater for water supply, when constructing hydraulic structures, exploiting various types of groundwater, when calculating permissible drops in water levels and radii of influence of water wells, when designing and implementing drainage and irrigation measures.

An aquifer is a layer or several layers of permeable rocks whose pores, cracks or other voids are filled with underground water. Several aquifers, hydraulically connected to each other, form an aquifer complex.

Verkhovodka is free-flowing groundwater that lies closest to the earth's surface and does not have a continuous distribution. Perched water is formed due to the infiltration of atmospheric and surface waters retained by impermeable or weakly permeable pinch out layers and lenses, as well as as a result of condensation of water vapor in rocks. Such groundwater is characterized by seasonal existence: in dry times they often disappear, and in periods of rain and intense snowmelt they appear again; are subject to sharp fluctuations depending on hydrometeorological conditions (amount of precipitation, air humidity, temperature, etc.). High water is also water that temporarily appears in swamp formations due to excess nutrition of swamps. Often, perched water occurs as a result of water leaks from water supply systems, sewers, swimming pools and other water-carrying devices, which can result in swamping of the area, flooding of foundations and basements. In the area of ​​distribution of permafrost rocks, perched water belongs to supra-permafrost waters.

The waters of the perched water are usually fresh, slightly mineralized, but are often contaminated with organic substances and have a high content of iron and silicic acid. Verkhodka, as a rule, cannot serve as a good source of water supply. However, if necessary, measures are taken to artificially preserve perched water: constructing ponds; diversions from rivers that provide constant power to operating wells; planting vegetation that delays snowmelt; creation of waterproof bridges, etc. In desert areas, by constructing grooves in clayey areas - takyrs, atmospheric waters are diverted to the adjacent area of ​​sand, where a lens of perched water is created, containing a certain supply of fresh water.

Gravity water - water in ground reservoirs, watercourses and pipes when they are not completely filled, as well as underground water that has a free surface (water mirror). Underground free-flow waters are either located in the first permeable layer from the earth's surface, forming perched water and groundwater, or they saturate the permeable layer of rocks located between water-resistant rocks (layers), without reaching its waterproof roof - the so-called interlayer free-flow waters. For practice, it is important that the level of free-flow water in underground mine workings (boreholes, wells, pits, etc.) without pumping is established at the depth of appearance of groundwater, in contrast to pressure water, the level of which is established below the point where the aquifer is opened.

Artesian waters (from the name of the French province of Artois (lat. AMeBsht), where these waters have long been used) - underground water enclosed between aquifer layers and under hydraulic pressure. They occur mainly in pre-anthropogenic deposits, within large geological structures, forming artesian basins.

Artesian waters opened artificially rise above the roof of the aquifer. With sufficient pressure, they pour out onto the surface of the earth, and sometimes even fountain. The line connecting the marks of the steady pressure level in the wells forms a piezometric level.

Unlike groundwater, which participates in modern water exchange with the earth's surface, many artesian waters are ancient, and their chemical composition usually reflects the conditions of formation. Initially, artesian waters were associated with trough-like structures. However, the conditions under which these waters were formed are very diverse; They can often be found in flexure-like asymmetric monoclinal bedding of strata. In many areas, artesian waters are confined to a complex system of cracks and faults.

Within the artesian basin, three areas are distinguished: supply, pressure and discharge (Fig. 45, 1). In the recharge area, the aquifer is usually elevated and drained, so the waters here have a free surface; in the pressure region, the level to which water can rise is located above the roof of the aquifer. The vertical distance from the top of the aquifer to this level is called the head.

Straight relief

Aquifers

horizons

Waterproof

Water level

Rice. 45. Artesian pool:

1 - diagram of the structure of the artesian basin: A- limits of distribution of artesian waters: A- food area, b- pressure area, V- unloading area; B- limits of groundwater distribution; N- pressure level above the ground surface; // 2 - pressure level below the surface of the earth; 2 - types of artesian basins (BSE).

Unlike the recharge area, where the thickness of the aquifer varies depending on meteorological factors, in the pressure area the thickness of the artesian horizon is constant over time. At the boundary between the recharge area and the pressure area, depending on the amount of incoming atmospheric water in different seasons, a temporary transition of water with a free surface into pressure water may occur. In the area of ​​discharge, water reaches the earth's surface in the form of rising springs. If there are several aquifers, each of them can have its own level, determined by the conditions of recharge and water flow. When the synclinal occurrence of layers corresponds to relief depressions, pressures in the lower horizons increase; when the relief rises, the piezometric levels of the lower horizons are located at lower elevations (see Fig. 45, 2). If two aquifers are connected through a borehole or a well, then with reversed relief, artesian water flows from the upper horizon to the lower one.

There is an artesian basin and an artesian slope (Fig. 46). In an artesian basin, the recharge area is adjacent to the pressure area; further along the direction of the underground flow there is an area of ​​discharge of the pressure horizon. In an artesian slope, the latter is located next to the feeding area.

Unloading area

Aquiferous

Hydroisohypses ---Hydroisopiesis -

Direction of water movement

Rice. 46. Artesian slope diagram (ASS).

Each large artesian basin contains waters of different chemical composition: from highly mineralized brines chloride type to fresh, slightly mineralized waters of the hydrocarbonate type. The former usually lie in the deep parts of the basin, the latter - in the upper layers. Fresh waters of the upper aquifers are formed as a result of infiltration of atmospheric precipitation and rock leaching processes. Deep, highly mineralized artesian waters are associated with altered waters of ancient marine basins.

Due to the wide variety of hydrogeological conditions, artesian basins are sometimes called water-pressure systems. The largest water pumping system in our country is the West Siberian artesian basin with an area of ​​3 million km."

Artesian basin - a basin of groundwater within one or more geological structures containing confined aquifers. The largest artesian basins in Russia are the West Siberian, Moscow, Caspian, etc.; abroad - Australian. Large basins of pressurized water exist in North Africa, as well as in the eastern part of Australia.

Moscow artesian basin- artesian basin located in the center of the East European Plain. In geostructural terms, it belongs to the southwestern part of the Moscow syneclise. The basin area is about 360 thousand km.” Aquifer complexes are confined to the thickness of carbonate-terrigenous rocks from Early Cambrian to Quaternary age, lying on a folded crystalline basement; in accordance with the general subsidence of the foundation from southwest to northeast, the thickness of sedimentary deposits varies from 100-300 to 4000-4500 m. The Moscow artesian basin is characterized by the presence of three vertical zones, differing in the characteristics of hydrodynamic and hydrochemical conditions.

The upper zone - a zone of intensive water exchange (intensive underground flow) - is characterized by good conditions for the infiltration of atmospheric waters, the interaction of individual aquifers, and the hydraulic connection of groundwater with surface watercourses and reservoirs. The conditions of nutrition, flow, discharge and formation of groundwater resources are closely related to the characteristics of the topography, climate, and the drainage effect of the river network. This zone with a thickness of 250-300 m contains predominantly fresh (up to 1 g/l) waters of the hydrocarbonate class.

Below there is a zone of difficult water exchange, where the movement of groundwater is very slow due to the great depth, weak influence of river drains, and slight fracturing of rocks. The removal of salts is difficult; sulfates and chlorides predominate in the water composition. The waters are brackish and salty with a mineralization from 5-10 to 50 g/l. The thickness of the zone is 300-400 m.

In the deepest parts of the artesian basin there is a zone of very slow water exchange. The speed of water movement and the processes of washing rocks here are negligible, brines of high concentration are developed - from 50 to 270 g/l, the composition of the water is chloride, sodium, the thickness varies from 400-500 to 1600-2000 m in the most sagging parts of the basin.

The fresh groundwater of the basin has long been one of the sources of water supply for Moscow and the entire Central Industrial Region of the European part of Russia. Groundwater resources of the Moscow artesian basin account for up to 40% of the total water resources of the basin. 15-20% of precipitation is used to feed aquifers. The greatest resources are found in coal aquifers, which are widely used for drinking and industrial purposes.

Salt waters and brines from zones of difficult and slow water exchange, related primarily to Devonian and Permian deposits, are used for medicinal and balneological purposes (Staraya Russa, Kashin, etc.). Low-mineralized waters (4 g/l) of the Upper Devonian horizons in the Moscow region are known as “Moscow mineral water”.

Underground brines - groundwater containing dissolved minerals in high concentrations. According to some classifications, underground brines include waters with a mineralization of over 50 g/l, according to others - over 36 g/l (based on the salinity of the waters of the World Ocean). Underground brines are widespread in sedimentary basins, where they usually lie below fresh and salt waters and are confined to the thickest part of the sedimentary cover. For example, in the basins of the East European Platform, the thickness of the zone of fresh groundwater varies from 25 to 350 m, salt water - from 50 to 600 m, brines - from 400 to 3000 m. Underground brines have also been identified in sedimentary strata lying under the bottom of some seas (Red and Caspian, Gulf of Mexico, etc.) and within the shelves (for example, near the Florida Peninsula), as well as in the zone of hypergene fracturing of crystalline shields (Baltic, Ukrainian, Canadian). In arid regions, underground brines saturate the bottom sediments of internal drainage reservoirs (for example, the Inder salt lakes) and salty sea bays and lagoons (Kara Bogaz Gol, Bocana de Verila in Peru, sebkhas on the Mediterranean coast of Africa and Arabia).

According to the predominant anion, chloride, sulfate and hydrocarbonate underground brines are distinguished. Of these, only chloride (sodium, calcium and magnesium) are widespread. In salt-bearing sedimentation basins, according to the conditions of occurrence, supra-salt, intra-salt and sub-salt underground brines are distinguished (pre-salt underground brines are predominantly sodium, their salinity does not exceed 300-320 g/l, intra-salt and sub-salt underground brines are usually multi-component, their salinity is up to 600 g/l l).

Underground brines are used to obtain table salt, iodine, bromine, lithium; are potential raw materials for the extraction of rubidium, cesium, boron, and strontium. Some underground brines are used for medicinal purposes in the form of brine baths.

Thermal waters (French) thermal- warm, from Greek. thermo- heat, heat) - underground waters of the earth's crust with a temperature of 20 ° C and above. The depth of the 20 °C isotherm in the earth's crust is from 1500-2000 m in areas of permafrost to 100 m or less in subtropical areas; at the border with the tropics, the 20 °C isotherm reaches the surface. In artesian basins at a depth of 2000-3000 m, wells tap water with a temperature of 70-100 °C or more. In mountainous countries (for example, the Alps, Caucasus, Tien Shan, Pamir), thermal waters come to the surface in the form of numerous hot springs (temperatures up to 50-90 ° C), and in areas of modern volcanism they manifest themselves in the form of geysers and steam jets ( here, wells at a depth of 500-1000 m reveal waters with a temperature of 150-250 ° C), which produce steam-water mixtures and vapors when they reach the surface (Pauzhetka in Kamchatka, Big Geysers in the USA, Wairakei in New Zealand, Larderello in Italy, geysers in Iceland and etc.).

The chemical, gas composition and mineralization of thermal waters are varied: from fresh and brackish hydrocarbonate and hydro-carbonate-sulfate, calcium, sodium, nitrogen, carbon dioxide and hydrogen sulfide to salt and brine chloride, sodium and calcium-sodium, nitrogen-methane and methane, in some places hydrogen sulfide.

Since ancient times, thermal waters have been used for medicinal purposes (Roman, Tajikistan, Tbilisi baths). In Russia, fresh nitrogen thermal baths, rich in silicic acid, are used by famous resorts - Belokurikha in Altai, Kuldur in the Khabarovsk Territory, etc.; carbon dioxide thermal waters - the resorts of the Caucasian Mineral Waters (Pyatigorsk, Zheleznovodsk, Essentuki), hydrogen sulfide - the So-chi-Matsesta resort (Sochi). In balneology, thermal waters are divided into warm (subthermal) 20-37 °C, thermal 37-42 °C and hyperthermal - over 42 °C.

In areas of modern and recent volcanism in Italy, Iceland, Mexico, Russia, the USA, and Japan, a number of power plants operate that use superheated thermal waters with temperatures above 100 °C. In Russia and other countries (Bulgaria, Hungary, Iceland, New Zealand, USA), thermal waters are also used for heating residential and industrial buildings, heating greenhouse complexes, swimming pools and for technological purposes (Reykjavik is completely heated by the heat of thermal waters). In Russia, heat supply has been organized for the microdistricts of the cities of Kizlyar, Makhachkala, Cherkessk; heating of greenhouse complexes in Kamchatka and the Caucasus. In heat supply, thermal waters are divided into low-thermal - 20-50 °C, thermal - 50-75 °C, high-thermal - 75-100 °C.

Mineral waters are underground (sometimes surface) waters characterized by a high content of biologically active mineral (less often organic) components and (or) possessing specific physical and chemical properties (chemical composition, temperature, radioactivity, etc.), due to which they have an effect on the human body therapeutic effect. Depending on the chemical composition and physical properties, mineral waters are used as an external or internal remedy.

Patterns of formation and distribution of mineral underground waters. The process of formation of mineral waters has not yet been sufficiently studied. When characterizing their genesis, the origin of the underground water itself, the gases present in it and the ion-salt composition are distinguished.

The formation of mineral waters involves the processes of infiltration of surface water, burial of sea water during sedimentation, release of constitutional water during regional and contact metamorphism of rocks, and volcanic processes. The composition of mineral waters is determined by the history of geological development, the nature of tectonic structures, lithology, geothermal conditions and other features of the territory. The most powerful factors shaping the gas composition of mineral waters are metamorphic and volcanic processes. The volatile products released during these processes (CCL, HC1, etc.) enter the groundwater and make it highly aggressive, promoting leaching of the host rocks and the formation of the chemical composition, mineralization and gas saturation of the water. The ion-salt composition of mineral waters is formed with the participation of processes of dissolution of salt-bearing and carbonate deposits, cation exchange, etc.

Gases dissolved in mineral waters serve as indicators of the geochemical conditions in which the formation of this mineral water took place. In the upper zone of the earth's crust, where oxidative processes predominate, mineral waters contain gases of air origin - nitrogen, oxygen, carbon dioxide (in small volumes). Hydrocarbon gases and hydrogen sulfide indicate a reducing chemical environment characteristic of the deep interior of the Earth; the high concentration of carbon dioxide allows us to consider the water to have formed under metamorphic conditions.

On the surface of the Earth, mineral waters appear in the form of springs, and are also removed from the depths by boreholes (the depth can reach several kilometers). For practical development, deposits of underground mineral waters with strictly defined operational reserves are identified.

On the territory of our country and foreign countries, provinces of mineral waters are distinguished, each of which is distinguished by hydrogeological conditions, features of geological development, origin and physical and chemical characteristics of mineral waters.

Quite isolated reservoir systems of artesian basins are provinces of salt and brine waters of varied ionic composition with mineralization up to 300-400 g/l (sometimes up to 600 g/l); they contain reducing gases (hydrocarbons, hydrogen sulfide, nitrogen). Folded regions and areas of rejuvenated platforms correspond to provinces of carbon dioxide mineral waters (cold and thermal) of varying degrees of mineralization. The areas of manifestation of the latest tectonic movements belong to the province of nitrogen, weakly mineralized alkaline, often siliceous thermal waters, etc. The territory of Russia is especially rich in carbon dioxide mineral waters (Caucasian, Transbaikal, Primorsky, Kamchatka and other provinces).

Depending on the structural location and associated hydrodynamic and hydrogeochemical conditions in our country, the following types of mineral water deposits are distinguished: deposits of platform artesian basins (Kashinskoye, Starorusskoye, Tyumenskoye, Sestroretskoye, etc.); foothill and intermountain artesian basins and slopes (Chartak, Nalchik, etc.); artesian basins associated with zones of ascending discharge of mineral waters (Nagutskoye, Essentukskoye); fissure vein waters of hydrogeological massifs (Belokurikhinskoye, etc.); hydrogeological massifs associated with zones of ascending discharge of mineral waters into groundwater horizons (Darasunskoye, Shivandinskoye, Shmakovskoye, etc.); ground mineral waters (Marcial waters, Uvildinskoye, Kisegachskoye, Borovoe, etc.).

Therapeutic effect of mineral waters. Mineral waters have a therapeutic effect on the human body through the entire complex of substances dissolved in them, and the presence of specific biologically active components (CO2, NgB, Ab, etc.) and special properties often determine the methods of their medicinal use. The main criteria for assessing the healing properties of mineral waters in balneology are the features of their chemical composition and physical properties.

Mineralization of mineral waters, i.e. the sum of all water-soluble substances - ions, biologically active elements (excluding gases), is expressed in grams per 1 liter of water. According to mineralization there are different

They have low-mineralized mineral waters (1-2 g/l), low (2-5 g/l), medium (5-15 g/l), high (15-30 g/l) mineralization, brine mineral waters (35- 150 g/l) and strong brine (150 g/l and above). For internal use, mineral waters with a mineralization of 2 to 20 g/l are usually used.

According to their ionic composition, mineral waters are divided into chloride (CH), hydrocarbonate (HCO3~), sulfate (EO/ -), sodium (14a), calcium (Ca -), magnesium (M^) in various combinations of anions and cations. Based on the presence of gases and specific elements, carbon dioxide, sulfide (hydrogen sulfide), nitrogen, bromide, iodide, ferrous, arsenic, silicon, radioactive (radon), etc. are distinguished. Based on temperature, cold (up to 20 ° C), warm (20-37 ° C) are distinguished. C), hot (thermal, 37-42 °C), very hot (high thermal, 42 °C and above) mineral waters. In medical practice, great importance is attached to the content of organic substances in low-mineralized waters, since these substances determine the specific properties of mineral waters. The content of these substances above 40 mg/l makes mineral waters unsuitable for internal use.

Special standards have been developed that make it possible to assess the suitability of natural waters for treatment (Table 40).

Table 40

Standards for classifying water as mineral

Mineral waters are used at resorts for drinking treatment, baths, swimming in therapeutic pools, all kinds of showers, as well as for inhalation and gargling for diseases of the throat and upper respiratory tract, for irrigation for gynecological diseases, etc. Mineral waters are also used externally.

Mineral waters are used internally and in non-resort settings, when imported bottled waters are used. Now in our country there are countless factories and workshops for bottling mineral water. Bottled water is saturated with carbon dioxide to preserve its chemical properties and taste. The water should be colorless and absolutely clean. Treatment with bottled mineral water must be combined with adherence to a certain regimen, diet and the use of additional therapeutic factors (physiotherapy, drug treatment, hormonal therapy, etc.).

Mineral waters, predominantly of low mineralization, and also containing calcium ions, have a pronounced diuretic (diuretic) effect and promote the removal of bacteria, mucus, sand and even small stones from the kidneys, renal pelvis and bladder. The use of mineral water is contraindicated, for example, in case of narrowing of the esophagus and pylorus of the stomach, sudden prolapse of the stomach, cardiovascular diseases accompanied by edema, impaired excretory ability of the kidneys, etc. Treatment with mineral waters should be carried out as prescribed by a doctor and under medical supervision.

Artificial mineral waters are made from chemically pure salts, the composition of which coincides with the composition of natural ones. However, complete identity of the composition of artificial and natural mineral waters is not achieved. Particular difficulties arise in simulating the composition of dissolved gases and the properties of colloids. Of the artificial mineral waters, only carbonic, hydrogen sulfide and nitrogen waters, which are used mainly for baths, are widely used. The Central Institute of Balneology and Physiotherapy (Moscow) has proposed methods for preparing some drinking mineral waters that have high therapeutic value (Essentuki No. 4 and 17, Borjomi, Batalinskaya). Every year the number of balneological drinking resorts and boreholes producing mineral waters increases.

Some mineral waters are used as a refreshing, thirst-quenching table drink that increases appetite and is consumed instead of fresh water, without any medical indications. In a number of regions of Russia, ordinary drinking water is quite highly mineralized and is quite reasonably used as a table drink. Groundwater of the sodium chloride type with a mineralization of no higher than 4-4.5 g/l (for hydrocarbonate waters - about 6 g/l) can be used as table mineral waters.