Detrital sedimentary rock. Chemical sedimentary rock. Clastic sedimentary rocks From which clastic rocks are formed

Clastic rocks

clastic rocks, sedimentary rocks, consisting entirely or preim. from fragments of various rocks (igneous, metamorphic or sedimentary) and minerals (quartz, feldspars, mica, sometimes glauconite, volcanic glass, etc.). Distinguish O. of the item cemented and uncemented, loose. In cemented O. g., Carbonates (calcite, dolomite), silicon oxides (opal, chalcedony, quartz), iron oxides (limonite, goethite, etc.), clay minerals, and a number of other O. G. p. often contain organic remains: shells of mollusks, etc., trunks and branches of trees, etc. The classification of o. g. P. Is based on a structural feature - the size of the debris. Coarse-detrital rocks, or Psephites, with a fragment size of more than 1 mm (unconsolidated - lumps, boulders, pebbles, crushed stone, gruss, gravel; cemented - Conglomerates, breccias (See Breccias), Gravelites, etc.); sandy rocks, or psammites, with a particle size of 1-0.05 mm (sands and sandstones); silty rocks, or aleurites, with a particle size of 0.05-0.005 mm (siltstones and siltstones); clayey rocks, or Pelites, with a particle size less than 0.005 mm (clays, mudstones, etc.). Sometimes the boundary between aleurites and pelites is drawn by a particle size of 0.001 mm... Clay rocks can be of both chemical and detrital origin. O. g. Of mixed composition are also distinguished, composed of fragments of various dimensions - sandy, silty, and clayey. These include widespread, especially among modern continental deposits, various loams and sandy loams. A further subdivision of the ore plant within the structural subtypes is made according to the mineral composition of the fragments and other signs. The O. g. Also includes products of volcanic eruptions: volcanic rubble, ash - loose rocks and their cemented varieties - tuffs, tuff breccias, and rocks transitional between clastic and volcanic rocks - tuffites and tuffaceous rocks (see Volcanic-sedimentary rocks).

With a dissected relief and high dynamics of the environment, coarse-detrital rocks are formed, in conditions of a flat relief and a low speed of water and air flows - sandy, silty and clayey rocks. Clay particles are deposited mainly in calm water. In the coastal part of the seas and oceans, pebbles and gravel are deposited on the beach and in shallow waters; as they move deeper into the basin, they are replaced by sands, silts and, finally, clayey silts at a depth below the level of waves and currents. However, there are pebbles and sands at great depths - the result of the action of various bottom currents and turbidity flows (See. Turbidity flows).

O. g. P. Is used as a building material, sands - in the glass and metallurgical industries. In river and sea sands there are placers of gold, platinum, precious stones, minerals titanium, tin, tungsten, rare and radioactive elements.

Lit .: Logvinenko NV, Petrography of sedimentary rocks (With the basics of research methods), 2nd ed., M., 1974; Rukhin L.B., Fundamentals of lithology, 3rd ed., L., 1969.

N.V. Logvinenko.

Great Soviet Encyclopedia. - M .: Soviet encyclopedia. 1969-1978 .

See what "Clastic rocks" is in other dictionaries:

Clastic rocks (a. Clastic rock, fragmented rock, detrital rock; n. Klastische Gesteine, Trummergesteine; f. Roches detritiques, roches clastiques, roches agregees; and. Rocas detriticas, rocas clasticas), sedimentary forges. breeds ... Geological encyclopedia

Rocks composed of fragments of older rocks and minerals. By the size of the fragments, coarse-clastic (psephites), sandy (psamites), silty (silts, siltstones) and clayey (pelites) rocks are distinguished ... Big Encyclopedic Dictionary

Rocks composed of fragments of older rocks and minerals. By the size of the fragments, coarse-detrital (psephites), sandy (psamites), silty (silts, siltstones) and clay (pelites) rocks are distinguished. * * * DECK ROCKS ... ... encyclopedic Dictionary

Rocks composed of fragments of older forges. rocks and minerals. By the size of the fragments, coarse-clastic (psephites), sandy (psamites), silty (silts, siltstones) and clay (pelites) rocks are distinguished ... Natural science. encyclopedic Dictionary

A type of sedimentary rock, consisting of fragments of other rocks and minerals (usually quartz, feldspars, mica, sometimes glauconite, volcanic glass). There are cemented rocks (conglomerates and breccias), in which ... ... Geographical encyclopedia

Natural aggregates of minerals of more or less constant composition, forming independent geological bodies that make up the earth's crust. The term "G. P." for the first time in the modern sense was used (1798) by the Russian mineralogist and chemist V.M. Severgin ... Great Soviet Encyclopedia

Rocks formed by the accumulation of mineral substances, mainly from the aquatic environment, during their compaction and cementation. Distinguish: chemical sediments (gypsum, rock salt), detrital (gravel, sand, clayey rocks), cemented ... ... Construction vocabulary

The solid crust of the globe and its entire solid framework are composed of mineral aggregates. G. rocks are those of these aggregates that play an essential role in the composition of the lithosphere, revealing in the main features the constancy of composition and structure in ... Encyclopedic Dictionary of F.A. Brockhaus and I.A. Efron

Accumulations of products of destruction of sedimentary rocks of various petrographic composition and various sizes, formed from loose or cemented fragments. Loose rocks varieties (mechanical deposits) sedimentary (boulders, ... ... Construction vocabulary

Rocks formed by sedimentation of matter in the aquatic environment, less often from the air and as a result of the activity of glaciers. Sedimentation occurs mechanically, chemically and biogenic. Sedimentary rocks are divided into clastic, chemical and ... ... encyclopedic Dictionary

SEDIMENTARY CLOSE, SANDY, CLAYY AND MIXED (SANDY-CLAY) ROCKS

Clastic rocks and their classifications

These classes include well-known loose rocks - sand, crushed stone, pebble, gravel; cemented rocks, among which the most famous is sandstone, as well as clay rocks - clay, loam, sandy loam.

These rocks differ greatly from each other in composition and properties, but in nature, the transition from clastic to clayey rocks is very gradual, with a large number of mixed differences, which makes it necessary to consider these classes within one section.

Classification. The section considers five classes of rocks - coarse, sandy, fine, clay and mixed. For brevity, let us agree to call them all together clastic and clayey. As can be seen, they are all classified by size, debris shape, cementation and connectivity (Table 3.5).

Sedimentary clastic, clayey and mixed rocks

Table 3.5

Particle structure and size, mm	Breed name
	Texture
	Unconsolidated		Cemented
	Angular	Rounded	Angular	Rounded
1. Coarse grains: more than 1000			Blocky	Blocky conglomerate
	Uncut boulders (stones)		Boulder	Boulder conglomerate
		Pebble		Conglomerate
				Gravelite
2. Medium detrital - sandy (0.05-2):	Sands (by predominant fraction): gravelly (rough)		Sandstones (by predominant fraction): gravelly (rough)
	silty (thin)		silty (thin)
3. Fine-grained - dusty: 0.002 ... 0.05			Siltstone
4. Micrograin - clayey: less than 0.002 (0.005)			Argillite
5. Mixed	Silty-clayey sand with crushed stone and gravel, pebble with sandy gravel aggregate, etc.		Sandy conglomerate, sandy gravel, etc.		loam,

Composition. These rocks consist of the products of mechanical and chemical destruction and transformation of other rocks on the earth's surface. In the overwhelming majority of cases, they are the soil-forming material, most of the construction and other environmental management is carried out on them, they are often called the word "soil".

In the composition of clastic and clayey rocks, there are three main components - fragments, cement and clay material.

1. Debris - the main constituent part of clastic rocks is stone material in the composition of blocks, boulders, pebbles, gravel, crushed stone, grains of sand that form sand, quartz mineral dust. All this can be represented by various rocky or semi-rocky rocks, and the name of the original rock can only be mentioned - granite crushed stone, limestone pebble, quartz sand. Cobblestone, rubble, pebble, paving stones - natural or specially processed and selected stone tens of centimeters in size, used in construction for paving roads and laying foundations.

According to the shape, two main types of fragments are distinguished - angular and rounded; there are also several transitional types between them (Fig. 3.12).

Fig. 3.12. Stone fragments of various shapes: and - angular; b - rounded (rounded); in - semi-rounded

The widespread moraine is usually called rubble loam, while the stone inclusions in it are closer to rounded pebbles than to angular rubble.

1.1. The fragments are angular in shape. They are formed during weathering and breaking off of pieces from the bedrock monolithic rock.

In nature, this process is most intensively developed on the slopes; the resulting debris accumulates at the foot of the slopes, forming talus. With a horizontal relief, angular fragments remain in place, and the weathering process rapidly fades with depth. This is how weathering crusts are formed (Fig. 3.13).

Fig. 3.13.

The rocks of talus and weathering crusts, depending on the size of the debris, are called lumps, gravel, grit, cartilage. They can serve as a building material in the places of their distribution, although crushed stone, blocks, etc. actually used in construction. much more often they are artificially crushed stones, mined in quarries by means of explosions. On their basis, it is possible to obtain more durable materials for construction than when using weathered and fissured natural stone, especially since the majority of the population of Russia lives in flat areas, where these taluses and weathering crusts are practically absent.

• 1.2. Rounded (rounded) wreckage acquire this form as a result of water treatment (sea surf, rivers, glacial streams), less often - by the wind. Boulders are formed from angular boulders, pebbles are formed from crushed stone, and gravel is formed from grit (fine crushed stone). The smaller the debris, the more often they are rounded. For example, sands with angular debris are found in nature, but extremely rare. Dusty fraction - quartz fragments 0.002-0.05 mm in size are always round. Due to their small size, they begin to demonstrate colloidal properties - they easily stick together, and when turbid, they slowly settle in water.
• 2. Cement. Some rocks in nature resemble in their constitution such well-known artificial materials as hardened cement mortar or concrete, in that they consist of stone fragments held together by cement. It is possible that the idea of \u200b\u200bcreating concrete was borrowed by people in nature. Natural cement is similar in composition to some chemical sedimentary rocks. It can be carbonate, siliceous, sulfate, ferruginous and clayey - then it is called clay aggregate. Carbonate cement is similar in composition to chemical limestone and is determined by reaction with an acid. Siliceous - the most durable and hardest of cements, sometimes it has a greasy sheen, does not react with acid. Sulfate is not strong, it is scratched with a fingernail, sometimes sugar-like crystals are visible on it. Ferrous cement is recognized by its rusty color. Clay cement is scratched with a fingernail, soaked in water.

Cement formation is possible in two ways:

• 1) under sea conditions with the simultaneous accumulation of chemical sediment together with debris;
• 2) due to the precipitation of chemical material from groundwater inside the clastic strata after its accumulation.

Rocks with the most common types of cementation are shown in Fig. 3.14.

Fig. 3.14. Rocks with different types of cement: and - basal cement; b - pore cement; in - contact

3. Clay minerals. In coarse rocks, clay minerals can act as a filler between stone particles and actually act as cement. When clay minerals are mixed with sandy and fine-grained material, so-called clay rocks are formed - loams, sandy loams and natural clays. Clay minerals at the same time acquire the role of the main component, giving the entire mixture the properties of clay rocks, the main of which are moisture capacity, water resistance and cohesion - the ability to become plastic when wet and solid when dry.

Structure, granulometric and mineral composition. These characteristics are closely related. The structure of the material is determined depending on the size of the particles. Particles of a certain size are usually called fractions. Fraction boundaries are taken according to GOST 25100-2011 "Soils", with very slight changes they repeat the boundaries adopted in geological literature, only the names of the fractions differ; geological ones are given in brackets (Table 3.6).

Table 3.6

Structures and approximate composition of clastic, clayey and mixed rocks

Structure and fraction - particle size	Approximate composition
1. Coarse-grained (psephites) - larger than 2 mm	Fragments of any rock
2. Medium detrital - sandy (psammites) - 0.05-2 mm	Quartz predominates, feldspar may be present, there are very few other minerals
3. Fine-grained - silty (silt) - 0.002-0.05 mm	Quartz - almost the entire faction
4. Micro-grained - clayey (pelites) - less than 0.002 mm (less than 0.005 mm)	Kaolinite, montmorillonite, glauconite and other clay minerals, quartz, limonite
5. Mixed - clastic-sandy, sandy-clayey, etc.	Various mixtures of particles of 1-4th fractions

It is known that the finer the material is crushed, the faster it dissolves and enters into chemical reactions. Therefore, among large fragments (blocks, boulders, rubble, pebbles), almost all rocks are found, with the exception of the most soluble ones - gypsum, anhydrite, rock and other salts. Among the fragments of medium size, quartz is found mainly - the most resistant to weathering mineral, less often feldspar, and even less often other minerals. Medium detrital rocks are sands.

Among the fine-grained (dusty) particles, there are almost no other minerals, except for quartz. Rocks - loess, silt, siltstone.

Micro-grained rocks are composed of kaolinite, montmorillonite, hydromica and other clay minerals. The rocks are pure clays.

Mixed rocks - most often a mixture of sandy, silty and clayey fractions - these are clays, loams and sandy loams. The terms "sandy-clayey" and "clayey rocks" are widely used, which are used synonymously.

The percentage by weight of particles of different fractions is called particle size distribution (by the grantees). To determine it, a soil sample is passed through a set of sieves with further weighing of each fraction. Further, according to a small set of rules, the breed is given a formally correct name (Table 3.7). This applies to unconsolidated coarse, sandy and partly some clayey rocks, which will be discussed below.

Table 3.7

Subdivision of coarse and sandy soils

The correct assignment of the name to sandy and clayey soils is an important task in geology and soil science. The type of soil (in fact, the name) determines the various tabular values \u200b\u200bof the parameters included in the calculations of the foundations, which is important for designers. Therefore, the particle size distribution, along with other laboratory properties of soils, is one of the most important indicators of properties and is massively determined during surveys.

The origin of clastic rocks shown schematically in Fig. 3.15.

As you can see, everything begins in mountainous conditions with weathering, collapses and crumbling of angular stone fragments - this is how natural lumps and crushed stone. In the process of weathering (chemical), also clay minerals, which are easily carried away by water, and if granites and gneisses, which are very common in nature, are destroyed, then detrital quartz with particles of sandy and dusty size is also formed.

Fig. 3.15.

Due to the force of gravity, slope processes, temporary water flows and rivers, angular debris reaches the sea coast. Here, material is added to it, formed due to the destruction of the coast by waves. In the surf zone, the stone material is additionally crushed, the debris is rounded, boulders, pebbles, gravel, sand and quartz dust- material aleurites. Some of the material dissolves. By waves and sea currents, sediments are carried to a great depth, where, possibly, cementation and transformation into cemented analogs take place - conglomerates, gravelstones, sandstones, siltstones.

Similar processes on a smaller scale can occur due to the geological work of mountain rivers, glaciers and glacial streams. If there is no rounding phase, then during carburizing of angular material, sedimentary breccias.

Tectonic breccias are formed in zones of tectonic faults. Clastic material is obtained by the movement of tectonic blocks along the planes of faults, and cementation is due to the release of chemical sediment from groundwater, which easily circulates through the fragmented zone.

Artificial pebble, artificial beach. If it is necessary to increase the area of \u200b\u200bthe natural pebble beach on the coast, rubble is brought in and dumped into the surf zone. The rounding speed of the wreckage depends on the strength of the original rock and is usually several months, after which the beach is ready for use again. The artificial beach must be regularly replenished with rubble and protected from erosion, since in nature there are constantly processes of rubbing pebbles and carrying them away by sea currents. Building up sandy beaches is done in a similar way, but protecting them from erosion is even more difficult.

The texture of clastic, sandy and mixed rocks. The rocks of this group have a wide variety of textures and constitution due to the diversity of the rocks themselves (Table 3.8).

In terms of density, rocks can be dense, porous, micro- and macroporous, fractured and weathered. Only well-cemented breccias, conglomerates, gravelstones, sandstones, and siltstones have dense textures among the rocks of this group. All unconsolidated rocks - boulders, pebbles, crushed stone, gravel, sand, silt, etc. are porous due to the gaps between debris and particles. Microporous - all clay rocks due to micropores invisible to the naked eye.

The porosity of unconsolidated clastic and clayey rocks can be 20-35% and exceed 50% for loess. Commonly used terms (dense clay, dense sand, etc.) are relative and denote the minimum porosity of these rocks, which is 10-25% by volume. For sandy and clayey rocks, porosity is measured during exploration and is an indicator by which the compression of these rocks at the base of structures is calculated.

According to the mutual arrangement of particles, clastic rocks, like most sedimentary rocks, are layered and non-layered. Severely compacted bedded varieties are sometimes called schisty because of their resemblance to the metamorphic schist group. In contrast, shale sedimentary rocks are soaked.

By the bonds between particles (this characteristic can also be attributed to the structure), clastic rocks are defined as unconsolidated (free-flowing, loose), cemented and cohesive (loose). The term "connected" is used in relation to sandy Table 3.8

Textures and some features of the composition of sedimentary clastic, clayey and mixed (clastic-clayey) rocks

Texture type	Characteristic
1. Texture determined by the density of addition
1.1. Dense	No pores are visible, no water is absorbed into a dry sample - cemented clastic rocks
1.2. Microporous	Inherent in clayey rocks. The exact porosity is determined in the laboratory. Some samples are light
1.3. Porous, fine-pored, cavernous	The pores are visible to the naked eye. This is inherent in poorly cemented and uncemented rocks.
1.4. Macroporous	The term is used only in relation to loesses that have not only microporosity, but also visible to the naked eye pores with a diameter of about 1 mm, called macropores.
1.5. Fissured	There are cracks in the rock
1.6. You are windy aya	Cracks and voids in the rock are expanded as a result of weathering processes. The breed is weakened
2. Textures determined by the relative position of particles in the rock
2.1. Layered: a) macro-layered	Visible only in the outcrop by the change in color, composition, and rock constitution
b) finely layered	Can be seen in samples
c) slate	Thin fine lamination of clayey rocks with a refractory and hard consistency. Samples are broken into platy blocks by bedding
2.2. Non-layered	The rocks are not layered - loess, moraine
3. Textures determined by bonds between particles
3.1. Cemented	Rock particles are bonded together with cement
3.2. Unconsolidated (loose, loose)	Particles of rock are not bonded to each other
3.3. Connected (loose)	Inherent in clayey rocks. The rock is connected by colloidal bonds between particles. The rock is plastic when soaked, it becomes hard when it dries, but it is neither monolithic nor free-flowing material

clayey rocks. They are neither rocky nor loose material. They are pliable and flowable when wet and become almost hard when dry.

Hydrogeological and engineering-geological properties of cemented clastic rocks. Cemented rocks can be both dense impermeable and porous, permeable to water - it all depends on the ratio of the intervals between the fragments and the amount of cement. They can also be fractured, and if the cemented rock contains carbonate or sulfate components, the development of karst is possible, which further increases the permeability. These rocks have the usual rock and semi-rock properties. As a base, they are quite strong and incompressible. Only sandstones and siltstones are widely used as material for crushing into crushed stone, although coarse-grained rocks can also be used. To obtain beautiful facing tiles, marble breccias are used, to obtain tiles laid on the floor - sandstones and siltstones. Strong, well-cemented sandstone is even used for making steps, as it gives a good rough surface. Thin-layered sandstone varieties do not need to be sawed - they produce irregularly shaped natural tiles and are suitable for laying on walkways.

Hydrogeological and engineering-geological properties of unconsolidated clastic rocks. All unconsolidated rocks have good permeability, water availability, form aquifers, suitable and convenient for exploitation. The larger the fragments, the greater the permeability, the greater the filtration coefficients (see Part II, Table 8.1). Pebbles, crushed stone, gravel in their permeability are second only to highly porous, fractured and karst rocks.

Sands are also permeable rocks. The sizes of grains of sand vary from 0.05 to 2 mm. Also, the filtration coefficient varies dozens of times - it is maximum in gravelly sands and minimum in silty sands.

Sands are the most common among unconsolidated clastic rocks. They often occur on the surface to form groundwater aquifers. Sands are often found in the section, and, being overlain by clayey rocks, form interstratal freshwater aquifers. For the purposes of construction design, coarse soils and sands in accordance with GOST 25100-2011 are classified according to particle size distribution, degree of water saturation, porosity and some other indicators determined by laboratory.

The presence of clay or organic aggregate greatly reduces the permeability of unconsolidated rocks. Pebbles with clay aggregate turn, in fact, into poorly permeable rocks. The permeability of clayey sands with organic matter decreases tenfold compared to similar rocks without aggregate. As the base and environment of structures, unconsolidated rocks are usually not difficult, with the exception of dusty and fine sands capable of showing quicksand properties and frost heaving. Boulders, boulders, pebbles, crushed stone, gravel - a weakly compressible base.

Clastic rocks.They consist of fragments of destroyed bedrock or minerals, sometimes with the remains of shattered fossil shells. Their classification is based on the size, degree of roundness and consolidation of fragments (Tables 13 and 14), which depend on the strength and resistance of the bedrock (destroyed) rocks to weathering processes, as well as the stage of rock development: weathering, denudation, accumulation, or diagenesis. So loose rocks from angular loose debris are products (result) of physical weathering; from rounded - weathering, transfer (denudation) and accumulation (sedimentation) of loose sediments. Cemented clastic rocks passed through the stage of diagenesis in their development, during which carbonate or siliceous minerals were formed between the clasts, or fine-clastic minerals - clays - were deposited. Loose rocks are usually young, Quaternary in age and lie close to the surface, while cemented rocks are older in age. Most of the cemented dense clastic rocks accumulate at the bottom of the seas and oceans, where many weathering products are ultimately transported, and therefore such rocks are also called terrigenous(demolished from the continents - land). For detrital rocks, the concept of "structure" is often confused with "texture", so it is possible to characterize simply the structure of rocks.

Crushed stone and grit consist of unrolled fragments of various most durable rocks and minerals and differ in the size of the fragments. They have eluvial (weathering products of rocks that remain in the place of their formation) and deluvial (formed when moving and accumulating rock debris on the slopes and at the foot of hills and

Table 12

Characterization of widespread sedimentary rocks and soils

Name and class (debris, chemical, biochemical)	Mineral composition (rock-forming) and chemical composition	Structure		Color and other distinctive properties	Class and varieties of soils (in terms of particle size distribution, water permeability, strength and compressibility, softening, plasticity, salinity, solubility, etc.)
		Texture	Structure
Sand, clastic Sandstone Conglomerate Limestones of different texture Diatomite Rock salt Anhydrite

Completed Checked

Table 13

Sedimentary clastic rocks (key)

To size debris, mm				Cemented			minerals		Structure
	Acute-angled	Rounded	Acute-angled		Rounded	Structure			Texture
clastic -> 2…>100	Lumps > 100 Crushed stone - Dresva -				Conglomerate	Various of the most durable breeds		Cemented rock structure is determined by cement		Loose, rounded or not rounded, debris or cement
debris,				Sandstone			Quartz, olivine, feldspars, pomegranate, etc.
debris,				Siltstones			Dust particles of quartz, etc.
clastic				Mudstones			Kaolinite, montmorillonite, etc.

Table 14

Basic structures of cemented clastic rocks

Name of structure groups	Name of the main structures	Features	Influence on the property of rocks
Psephitic	Pebble Gravel Crushed stone Grit	Typical for conglomerates: rounded debris 10 ... 100 mm in size Typical for gravel stones: rounded debris ranging in size from 2 ... 10 mm It is observed in breccias and gesso. Characteristic is the non-rounded form of fragments with a diameter of 10 ... 100 mm (crushed stone) and 2 ... 10 mm (grit)	Properties and stability, in addition to the size of the fragments, depend on their mineral composition, the nature and type of cement
Psamite	Coarse-grained Medium-grained Fine-grained	Observed in sandstones at grain size	The properties and stability of rocks, in addition to the size of the fragments, depend on the mineral composition of the fragments, the nature and type of cement.
Aleurite	siltstone siltstone	Typical for grain size siltstones 0.1 ... 0.05 mm Typical for siltstones with a grain size of 0.05 ... 0.005 mm	Unstable to weathering: dry - solid, moist become soft, swell in water, sometimes soak until complete loss of cohesion
	Pelite	Typical for mudstones and compacted clays less than 0.005 mm

mountains) origin, lie in the idea of \u200b\u200bthin covers and trails at the foot, covering almost the entire earth's surface. Since the most durable bedrocks are preserved in the form of crushed stone and gruss, these deposits have an average strength coefficient of 1.5.

Pebbles and gravel They differ from crushed stone and gruss in the roundness of the fragments, which occurs during prolonged transport over considerable distances. The degree of rounding and sorting is extremely varied. They are divided into river, lacustrine, sea and glacial sediments, which are deposited in the form of layers and lenses. The voids between pebbles and gravel are large enough. Pebble and gravel grains practically do not have the ability to capillary rise of water, but they are well permeable and easily give off water.

Pebbles and gravel are of great practical importance as building material that can be easily sorted and processed. They are used for the preparation of concrete, in road construction and when installing filters in hydraulic structures.

Sands - loose rock, consisting of rounded or acute-angled grains of various minerals and rocks of different colors. Quartz sands predominate, but it is not uncommon for it to contain grains of feldspars, micas, magnetite and other minerals. Sometimes sands are found, consisting almost exclusively of grains of dolomite, magnetite, shale, fragments of shells or rocks. According to the conditions of formation, sands can be river, lacustrine, sea, glacial and dune sands, differ in layering, roundness, mineral composition and other properties.

The porosity of sands is significantly less than the porosity of other clastic rocks (loess, clay); it is usually equal to 30 ... 40%. The very important properties of sand include its peculiarity not to change the volume when drying and moistening and the ability not to absorb, pass through itself and give up water. Sand saturated with water can flow and create quicksands on the slopes. Sand that is saturated with water but is unable to move and erode can be a reliable base. Sands have a small capillary rise of water. The strength factor is 0.5 ... 0.6. Filtration coefficient 1 ... 1400 cm / h.

Sands are of great practical importance as a material for construction purposes, for the manufacture of faience, porcelain and glass; as a material for filtration in plumbing installations and other purposes.

Loess - yellowish-white, light, porous rock, a mixture of the smallest grains (0.05 ... 0.005 mm) of quartz, clay particles and calcite, heavily atomized, partly in the form of shelllike tiny balls, when rubbed turns into powder. Differs in high adhesion of particles and can form steep multi-meter cliffs. The loess contains many thin vertical tubes with traces of plant roots; many calcareous nodules (cranes or loess pupae) of bizarre shape. Typical loess is characterized by the absence of bedding. It is widespread on the earth's surface and occupies about 4% of the land. Most scientists consider a typical loess to be an eolian formation, however, there are hypotheses about its soil-eluvial, deluvial, proluvial, and even lacustrine-glacial origin. Loess belongs to specific soils due to its engineering and geological characteristics: in dry form, it can serve as a base for structures, but when moistened, it is subject to strong compaction, as a result of which significant subsidence is obtained. The subsidence of loess is a consequence of its high porosity and the action of water, which changes the structure of the loess. Strength coefficient 0.8, for liquefied loess 0.3. Dust filtration coefficient 0.51 ... 1.62 cm / h.

Clays - finely dispersed rocks, which include mainly clay minerals - products of chemical decomposition (hydrolysis) of silicates, mainly feldspars. Along with clay minerals

- kaolinite, montmorillonite and others, clays contain impurities in larger or smaller amounts of particles of quartz, feldspars and other minerals, including iron hydroxides - brown limonite. Clay rocks are the most common on the earth's surface and among sedimentary rocks, accounting for 50% of their total volume.

Clays are divided into fatty and skinny... The first ones are greasy to the touch, their color is most often gray, light gray, greenish gray. The content of kaolinite in them is high - more than 40 ... 70%. These clays are highly resistant at high temperatures. The second - skinny clays - are less greasy to the touch, and consist of the smallest particles of feldspars and quartz, as well as kaolinite in an amount of less than 40 ... 10%. They are painted mainly in yellow, yellow-brown, red-brown colors of various shades with iron oxides.

According to the conditions of formation, clays are divided into primary, or residual, and secondary, or sedimentary clays. Residual clays are products of hydrolysis of silicates and mainly feldspars. Secondary clays were formed at the expense of primary clays by moving them in a horizontal direction and re-deposition into reservoirs and depressions, they are distinguished by better sorting and fat content.

Clays in the dry state are hard and constitute a dense, pulverized rock. They have significant porosity; dry clays vigorously absorb water and, having become plastic, give up this water very slowly (see Table 9). At the same time, they noticeably increase in volume - they swell. Clays are distinguished by high water absorption - they are able to hold up to 70% of their volume of water, by capillary rise (up to 3 ... 7 meters) and, being saturated with water, are waterproof (waterproof). They contribute to the development of landslides when the slopes are sufficiently steep; as cover layers, they provide artesian (pressure) waters. Under external loading, unconsolidated clays are strongly compressed, but this compression is very slow and can last for hundreds of years. Heavy buildings built on such clays can produce significant and often uneven rainfall.

Clay soils include sandy loam, loam and clay. Sandy loam is a transitional rock from sands to clays. The amount of clay particles in them is 3 ... 10%. Wet sandy loam crumbles when rolled in hands. The filtration coefficient of sandy loam is 0.01 ... 36 cm / h. Loam contains more clay particles - 10 ... 30%, resembles clay in its properties, however, wet loam cracks when rolling and bending in hands. Loam filtration coefficient 0.06 ... 5.0 cm / h. Clay contains clay particles of more than 30%, due to which a tourniquet made of wet clay can be rolled into a steering wheel. Clay strength coefficient 1.0. Filtration coefficient 0.000002 ... 0.001 cm / h. Clay rocks are interbedded with each other and quickly pinch out over the area of \u200b\u200bdistribution.

Kaolin clays are used in the porcelain and stationery industries, oily clays are used as refractory materials, and thinner clays are used for brick, tile and pottery production. Cloth clays, characterized by their ability to absorb fats and oils, are used for cleaning wool, cloth, etc. Glauconite clays produce a good green mineral paint, from ferruginous clays - red paints, umber, sienna, ocher.

Argillite (or shale) Is a very compacted fine-clastic clayey rock with pronounced lamination, passing in places into schistosity. It consists of the smallest particles of kaolinite, flakes of muscovite, chlorite, the smallest grains of quartz with an admixture of carbonaceous particles and iron hydroxides, therefore it often has a color that is dark to black or with brown shades. Argillaceous shales occur in the form of layers, horizontal or crumpled into folds, broken by faults.

Clay shales are widespread, usually in folded areas: in the Caucasus, the Urals, etc. Varieties of dark gray color, which have thin platy jointing, are called roofing shales. Slates are black due to the presence of carbonaceous matter. Bituminous and oil shales are sheet rocks of black and dark gray color, rich in bitumen.

Shale with good thin-slab jointing is used as a very resistant roofing material. They are used for making stair treads, plinths, floor tiles, window sills, panels, table boards, washbasins. Slates, which do not contain any admixture of ore minerals, are used in electrical engineering instead of marble. Waste from roofing and shale production is used to make asphalt and artificial road stones.

Engineering-geological characteristics - shales differ from clays by a much higher hardness. The strength coefficient of strong clay shale is 4. Ultimate compressive strength 60 ... 200 MPa.

Sandstone - cemented dense-bedded sands of varying strength, formed as a result of diagenesis, compaction of loose sediments under the weight of overlying sediments. According to the absolute size, coarse-grained, medium-grained and fine-grained sandstones are distinguished. They consist predominantly of the most abundant and physically and chemically resistant quartz. Depending on the mineralogical composition of the cement, sandstones are subdivided into siliceous, calcareous, clayey, ferruginous, and gypsum (see Tables 9, 13 and 14). They occur in the form of layers and lenses.

Sandstones are widespread in Karelia, in the central regions of Russia, in the Volga region, in the Urals. Sandstones differ in the mineral composition of sand grains: monomineral (usually quartz), polymineral arkose (consist of quartz, feldspars and mica) and graywacke (consist of fragments of various rocks, amphiboles, quartz, feldspars and mica), as well as cement (see Table 9).

Sandstone is widely used as a building material, especially where other stone building materials are not available. Silica-rich (at least 97%) varieties of sandstones are used as valuable dinas raw materials. Sandstones with siliceous cement are widely used in construction as a rubble material, some varieties are successfully used for the manufacture of millstones.

Depending on the porosity, moisture content, cementing agent, as well as on the structure and size of grains, the mechanical strength of sandstones varies within wide limits (see Table 9). Porous sandstones often contain artesian waters, oil, and combustible gases. Compressive strength ranges from 40 to 140 MPa. Strength factor 2 ... 15.

Breccia and conglomerate - cemented rocks, consisting, respectively, of non-rounded acute-angled and rounded fragments of rocks (see Table 13) and finer cementing substance. The composition of fragments of breccias, in comparison with conglomerates, is less complex, since the area of \u200b\u200bdemolition of fragments that compose breccias is much smaller than that of fragments that make up conglomerates. Fragments usually belong to one or a few rock types. Debris in conglomerates was transported over long distances from many places for a long time. The composition of the cement can be different: lime, siliceous, ferruginous, clayey. Breccias are characterized by a heterogeneous composition of cement as opposed to a homogeneous composition of fragments.

Breccia is formed during tectonic and landslide processes by the accumulation of products of destruction (debris) of rocks at the foot of the slopes. Volcanic breccias are formed by cementation of coarse volcanic ejections; tuff breccias - a significant amount of ash. Conglomerates - from debris that accumulated along the shores of seas, mountain rivers and lakes. The fragments are cemented by various chemical compounds (lime, etc.) falling out of the water and settling fine clay particles. They occur in the form of layers of low thickness - tens, sometimes the first hundreds of meters. Distributed mainly in folded areas: in the Urals, the Caucasus, as well as in landslide zones. Due to the angular shape of the fragments, breccias are stronger than conglomerates and are more suitable as building stones. As a facing stone, it is prized for the beauty of breccia.

Thus, clastic rocks are very diverse in composition, structure, and forms of occurrence; pinch out and replace each other both along the strike of the rocks (in area) and at depth. Continental modern clastic usually loose rocks have a thickness of the first meters up to hundreds of meters, covering the entire earth's surface. It is in these rocks, among the alternation and pinching out of clastic and clayey rocks, that builders often have to carry out their work. Marine terrigenous clastic rocks, extending over large areas, have a thickness of hundreds and even thousands of meters, as well as more ancient age. On flat areas within platforms, they lie under a cover of continental sediments, in folded areas they often lie close to the earth's surface and fall into the field of engineering activities.

Table 15

Chemogenic and biogenic rocks (key)

Chemical composition	Name	Main rock-forming minerals	Structure	Texture
	Rock salt Sylvinite		Crystalline	Massive Striped Layered
Sulphates	Anhydrite	Anhydrite
Carbonates	Limestone	Clay minerals (40-50%)
			Biomorphic Biosomatic Fine - fine - grainy	Densely layered, Fine pore Biogenic
Siliceous rocks	Diatomite	(a. clastic rock, fragmented rock, detrital rock; n. klastische Gesteine, Trummergesteine; f. roches detritiques, roches clastiques, roches agregees; and. rocas detriticas, rocas clasticas), - sedimentary rocks, consisting entirely or mainly of fragments various rocks (igneous, metamorphic or sedimentary) and minerals (feldspars, micas, sometimes glauconite, volcanic glass, etc.). Distinguish between cemented and unconsolidated (loose) detrital rocks. In cemented clastic rocks, carbonates (calcite, dolomite), silicon oxides (opal, chalcedony, quartz), iron oxides (limonite, goethite, etc.), clay minerals, and a number of others serve as a binder. Facing rocks often contain organic remains: whole shells or their fragments - molluscs, corals, crinoids and others, tree trunks and branches, etc. The classification of facing rocks is based on a structural feature - the size of the fragments. The following are distinguished: coarse-detrital rocks, or psephites, with fragments of more than 1 mm (unconsolidated - lumps, boulders, pebbles, crushed stone, gruss, gravel; cemented - conglomerates, breccias, gravelites, etc.); sandy rocks, or psammites, with a particle size of 1-0.05 mm, according to another classification, 1-0.1 (2-0.05 mm) (sands and sandstones); silty rocks, or silts, with a particle size of 0.05-0.005 mm (silts and siltstones); clayey rocks, or pelites, with a particle size of less than 0.005 mm (clays, mudstones, etc.). The boundary between aleurites and pelites is drawn by a particle size of 0.005 (0.01 in other classifications) mm. Clay rocks can be both chemical and clastic origin. Clastic rocks of mixed composition are also distinguished, composed of fragments of various dimensions - sandy, silty and clayey. These include widespread, especially among modern continental deposits, various loams and sandy loams. Further subdivision of clastic rocks within structural subtypes is carried out according to the mineral composition of fragments and other characteristics. The clastic rocks also include the products of volcanic eruptions: volcanic rubble, ash (loose rocks and their cemented varieties - tuffs), tuff breccias and rocks that are transitional between clastic and volcanic rocks - tuffites and tuffaceous rocks (see volcanic-sedimentary rocks). With a dissected relief and high dynamics of the environment, coarse-detrital rocks are formed, in conditions of a flat relief and a low speed of water and air flows - sandy, silty and clayey rocks. Clay particles settle mainly in calm water. In the coastal part of the seas and oceans, pebbles and gravel are deposited on the beach and shallow water, as they move deeper into the basin, they are replaced Sedimentary rocks occupy an impressive area of \u200b\u200bthe globe. These include most of all the minerals that our planet is so rich in. Most of the sedimentary rocks are located on the mainland, continental slope and shelf, and only a small part - at the bottom of the seas and oceans. Origin of sedimentary rocks Under the destructive influence of sunlight, temperature fluctuations, water, solid igneous rocks are weathering. They form fragments of various sizes, which gradually disintegrate to the smallest particles. Wind and water carry these particles, which at some stage begin to settle, thereby forming loose accumulations on the surface of the land and at the bottom of water bodies. Over time, they harden, thicken, acquire their own structure. This is how sedimentary rocks are formed. Fig. 1. Sedimentary rocks Like metamorphic rocks, sedimentary rocks are secondary rocks. They lie only on the surface of the earth's crust, occupying about 3/4 of the area of \u200b\u200bthe entire planet. Since almost all construction work is carried out on sedimentary rocks, it is very important to know perfectly the properties, composition and "behavior" of this type of rocks. These and many other issues are dealt with by the science of engineering geology. The main feature of sedimentary rocks is layering, which is unique for each natural compound. As a result of shifts in the earth's crust, the original forms of bedding of sedimentary rocks are disturbed: all kinds of breaks, cracks, faults, folds appear. TOP-4 articleswho read along with this Fig. 2. Layering of sedimentary rocks Classification of rocks The deposition process can take place in various ways. Depending on its specificity, several main groups of sedimentary rocks are distinguished: clastic - are formed under the influence of weathering and further transfer of igneous rock particles; chemogenic - the result of the separation and precipitation of substances that are formed from saturated aqueous solutions; biochemical - are formed as a result of chemical reactions with the participation of living organisms; biogenic - the result of decomposition of the remains of plant and animal organisms. In nature, mixed groups of sedimentary rocks are often found, the formation of which was influenced by several factors at once. So, one of the striking examples of mixed sedimentary rocks is limestone, which can equally be of chemogenic, organogenic, biochemical or clastic origin. Fig. 3. Limestone What have we learned? Sedimentary rocks occupy vast areas of the Earth's surface. They can be located both on land and at the bottom of the seas and oceans. Any sedimentary rock is formed from destroyed and altered igneous rocks. The classification of rocks is based on the features of the sedimentation process, which can occur under the influence of many factors. Test by topic Assessment of the report Average rating: 4.3. Total ratings received: 331.   It might be useful to read: Materials management systems in production logistics; Analysis of the material flow management system of the production enterprise ojsc corporation vsmpo-avisma; Chemical sedimentary rock; Social poster stages of building a social poster; Features of making and implementing management decisions - abstract; Protection of honor, dignity and business reputation Dignity and business reputation; The main directions of financial management of the enterprise; Strong company copy - what's important and how to write it;