Determination of the angle of repose of sandy soil in dry and wet conditions. Construction earthworks Angle of repose clay

Angle of repose

Angle of repose

Angle of repose - the angle formed by the free surface of a loose rock mass or other bulk material with a horizontal plane. Sometimes the term "angle of internal friction" can be used.

Particles of material located on the free surface of the embankment experience a state of critical (limiting) equilibrium. The angle of repose is related to the coefficient of friction and depends on the roughness of the grains, the degree of their moisture, particle size distribution and shape, as well as on the specific gravity of the material.

At the angles of natural slope, the maximum permissible angles of the slopes of ledges and sides of open pits, embankments, dumps and piles are determined. angle of repose from various materials

A list of the various materials and their angle of repose. Data are approximate.

see also

Notes

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See what "Angle of repose" is in other dictionaries:

angle of repose - The limiting angle formed by the free slope of loose soil with a horizontal plane, at which there is no violation of the stable state [Terminological dictionary for construction in 12 languages \u200b\u200b(VNIIIS Gosstroy USSR)] angle ... ... Technical translator's guide

The maximum angle of inclination of the slope, folded by the g. P., At which they are in equilibrium, that is, do not crumble, do not slide. Depends on the composition and condition of the g. P., Composing the slope, their water content, and for clay p. And the height of the slope. Geological ... Geological encyclopedia

Angle of (natural) slope - (Böschungswinkel) - the angle relative to the horizontal formed when pouring bulk material. [STB EN1991 1 1 20071.4] Term heading: General, placeholders Encyclopedia headings: Abrasive equipment, Abrasives, Highways ... Encyclopedia of terms, definitions and explanations of building materials

angle of repose - The extreme steepness of the slope, at which the loose deposits composing it are in equilibrium (do not crumble). Syn .: natural slope ... Geography Dictionary

angle of repose - 3.25 angle of repose: The angle formed by the generatrix of a slope with a horizontal surface when filling bulk material (soil) and close to the value of its angle of internal friction. Source … Dictionary-reference book of terms of normative and technical documentation

ANGLE OF NATURAL SLOPE - the angle at which the unreinforced sandy slope still maintains equilibrium, or the angle at which free sand is located. U. e. O. determined in air dry state and under water ... Dictionary of Hydrogeology and Engineering Geology

angle of repose - the angle at the base of the cone, formed when free pouring bulk material on a horizontal plane; characterizes the flowability of this material; See also: Angle contact angle contact angle ... Encyclopedic Dictionary of Metallurgy

The limiting angle formed by the free slope of loose soil with a horizontal plane, at which there is no disturbance of the stable state (Bulgarian; Български) ъгъл on the natural slope (Czech; Čeština) úhel přirozeného ... ... Construction dictionary

Ecological Dictionary

ANGLE OF NATURAL SOIL SLOPE - (soil) the largest possible angle, which forms a stable slope with a horizontal surface of an embankment of dry soil (soil), or wet soil (soil) under water. Ecological Dictionary, 2001 Angle of natural slope of the soil (ground) ... ... Ecological Dictionary

Angle of repose or angle of rest - This is the angle between the plane of the base of the stack and the generatrix, which depends on the type and condition of the cargo. Angle of repose - the maximum angle of inclination of the slope of granular material that does not possess adhesion, i.e., free-flowing material. Loose and porous bulk cargoes have a greater rest angle than solid bulk cargoes. The angle of rest increases with increasing humidity, and during long-term storage of many bulk cargo, the angle of rest increases due to compaction and caking. Distinguish between the angle of repose at rest and in motion. At rest, the angle of repose is 10 - 18 ° greater than when in motion (eg on a conveyor belt).

The value of the angle of repose of the cargo depends on the shape, size, roughness and uniformity of the cargo

particles, moisture mass of the cargo, method of filling it, initial state and material of the supporting surface.

Are applied different methods determining the value of the angle of repose; the most common are methods of filling and caving.

The experimental determination of the shear resistance and the main parameters of the load is usually performed by the methods of direct shear, uniaxial and triaxial compression. Testing the properties of a load using direct shear methods is applicable to both ideal and cohesive bulk solids. The test method for uniaxial (simple) compression - crushing is applicable only to assess the total shear resistance of cohesive bulk bodies under the conditional assumption that a uniform stress state is maintained at all points of the test specimen. The most reliable test results for the characteristics of a cohesive bulk body are provided by the triaxial compression method, which allows one to study the strength of a load sample under all-round compression.

Determination of the angle of repose of fine-grained substances (particle size less than 10 mm) is carried out using an "inclined box". The angle of repose in this case is the angle formed by the horizontal plane and the upper edge of the test box at the moment when the mass shedding of the substance in the box just begins

The ship's method for determining the angle of repose of a substance is used in the absence of a tilt box.

ka ". In this case, the angle of repose is the angle between the generatrix of the load cone and the horizontal

plane.

Angle of repose. Methods for determination in natural conditions

Angle of reposeor rest angle - uhthen the angle between the plane of the base of the stack and the generatrix, which depends on the type and condition of the cargo. Angle of repose - the maximum angle of inclination of the slope of granular material that does not possess adhesion, i.e., free-flowing material.

In practice, data on angle of reposeare used when determining the area of \u200b\u200bstacking cargo, the amount of cargo in the stack, the volume of intra-bilge trimming, when calculating the pressure values \u200b\u200bof the cargo on the walls enclosing it

Various methods are used to determine the angle of repose; the most common methods are fillingsand collapse.

Experimental definition shear resistanceand the main parameters of the cargo is usually made by methods straight cut, uniaxialand triaxial compression.

Determination of the angle of repose fine-grained substances(particle size less than 10 mm) is produced using " tilting box". The angle of repose in this case is the angle formed by the horizontal plane and the top edge of the test box at the moment when the bulk of the substance in the box begins to fall.

Ship methoddetermination of the angle of repose of the substance is used in the absence of a "tilt box". In this case, the angle of repose is the angle between the generatrix of the load cone and the horizontal plane.

The practice of measuring the angles of repose in natural conditions shows that their value is somewhat changesdepending on the filling methodcargo (jet or rain), massesinvestigated cargo, heights, with which the experimental filling is performed.

Convenient for quick measurements mohs way, in which the grain is poured into a rectangular box with glass walls measuring 100x200x300 mm at 1/3 of its height. The box is carefully rotated 90 ° and the angle between the surface of the grain and the horizontal (after turning) wall is measured.

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1. General Provisions

Purpose and types of earthworks

The volume of earthworks is very large, it is available during the construction of any building and structure. Excavation works account for 10% of the total labor intensity in construction.

The following main types of earthworks are distinguished:

Site layout;

Pits and trenches;

Road beds;

Dams;

Dams;

Channels, etc.

Earthen structures are divided into:

Permanent;

Temporary.

The permanent ones include pits, trenches, embankments, and excavations.

Requirements are imposed on permanent earthen structures:

Must be durable, i.e. resist temporary and permanent loads;

Sustainable;

Good resistance to atmospheric influences;

It is good to resist erosion actions;

They must have no settling.

Temporary earthworks are carried out for subsequent construction and installation work. These are trenches, pits, lintels, etc.

Basic construction properties and soil classification

Soil is called the rocks that occur in the upper layers. crust... These include: vegetative soil, sand, sandy loam, gravel, clay, loess-like loam, peat, various rocky soils and quicksands.

The following soils are distinguished by the size of mineral particles and their mutual connection :

Connected - clay;

Disjointed - sandy and loose (in a dry state), coarse unconsolidated soils containing more than 50% (by mass) fragments of crystalline rocks larger than 2 mm;

Rocky - igneous, metamorphic and sedimentary rocks with a rigid bond between grains.

The main properties of soils that affect the production technology, labor intensity and cost of earthworks include:

Bulk weight;

Humidity;

Erasability

Clutch;

Looseness;

Angle of repose;

The bulk mass is the mass of 1 m3 of soil in its natural state in a dense body.
The bulk mass of sandy and clayey soils is 1.5 - 2 t / m3, rocky not loosened up to 3 t / m3.
Moisture - the degree of saturation of soil pores with water

g b - g c - soil mass before and after drying.

With a moisture content of up to 5%, soils are called dry.

With a moisture content of 5 to 15%, soils are called low-moisture.

With a moisture content of 15 to 30%, soils are called wet.

With a moisture content of more than 30%, soils are called wet.

Adhesion is the initial shear resistance of the soil.

Adhesion of soils:

Sandy soils 0.03 - 0.05 MP

Clay soils 0.05 - 0.3 MP

Semi-rocky soils 0.3 - 4 MPa

Rocky over 4 MPa.

In frozen soils, the adhesive force is much higher.

Looseness - this is the ability of the soil to increase in volume during development, due to the loss of communication between particles. The increase in the volume of the soil is characterized by the coefficient of loosening K p.

After compaction, the loosened soil is called the residual loosenedness K op.

Angle of repose characterized by physical properties soil.

The value of the angle of repose depends on the angle of internal friction, adhesion force and pressure of the overlying layers.

In the absence of adhesion forces, the limiting angle of repose is equal to the angle of internal friction.

The steepness of the slope depends on the angle of repose. The steepness of the slopes of excavations and embankments is characterized by the ratio of height to placement m - slope coefficient.

Angles of repose of soils and the ratio of the height of the slope to the laying

Soil erosion - entrainment of particles by flowing water. For fine sands, the highest water speed should not exceed 0.5-0.6 m / s, for coarse sands 1-2 m / s, for clayey soils, 1.5 m / s.

According to production standards, all soils are grouped and classified according to the degree of difficulty of development by various earth-moving machines and by hand:

For single-bucket excavators - 6 groups;

For bucket excavators - 2 groups;

For manual development - 7 groups, etc.

Counting the volume of earthworks

In the practice of construction, it is necessary mainly to calculate the volume of work on the vertical layout of sites, the volume of excavations and the volume of linear structures (trenches, road beds, embankments, etc.).

The volume is calculated in the working drawings and specified in the work production project.

Earthworks projects should include a cartogram of earthworks, a bill of volumes of embankments and excavations and a general soil balance

The project should contain the volume and direction of movement of the soil masses in the form of a statement or cartogram.

The technology of development, soil transportation, backfilling and compaction must be thought out.

The project should include a calendar schedule of earthworks, human and material resources and the choice of a set of machines should be indicated.

When calculating the volume of excavation of pits, trenches, excavations of embankments, they use all the known geometry formulas.

With complex shapes of cuts and embankments, they are divided into a number of simpler geometric bodies, which are then summed up.

Determination of the volume of soil masses in the development of pits

In most cases, the pit is a truncated rectangular pyramid, the volume of which is determined by the formula :

The entrance trench is determined by the formula:

Determination of the volume of soil masses when constructing linear structures

The volume of earthworks for linear structures of embankments, excavations, trenches can be calculated using the formula:

With a slope not exceeding 0.1, you can use the F.F. Murzo formula:

m is the slope factor.

If the slope exceeds 0.1, then use the formula

Calculation of volume on curves (Tulden's formula):

r - radius of curves

α - central angle of rotation

Calculation of the volume of earthworks when planning sites

It is most expedient to design the site layout so that the zero balance of earth masses is observed, i.e. redistribution of earth masses on the site itself, without delivery or removal of soil.

The volume of earthworks is determined based on the cartogram.

The site plan is divided into squares with sides from 10 to 50 m, depending on the terrain. For more complex terrain, the squares are divided into triangles.

The average elevation of the site surface, when dividing it into squares, is determined by the formula:

ΣH 1 - the sum of the marks of the points where there is one vertex of the square;

ΣH 2 - the sum of the marks of the points where there are two vertices of the square;

ΣH 4 - the sum of the marks of the points where there are four vertices of the square;

n - The number of squares.

When broken down into triangles, using the formula:

ΣH 1 - the sum of the marks of the points where there is one vertex of the triangle;

ΣH 2 - the sum of the marks of the points where there are two vertices of the triangle;

ΣH 3 - the sum of the marks of the points where there are three vertices of the triangle;

ΣH 6 - the sum of the marks of the points where there are six vertices of the triangle;
n - the number of squares.

As a rule, additional earthworks in the form of embankments and recesses are always erected on the planned site.

To ensure a zero balance of earthworks, the construction of these structures is taken into account by introducing an amendment to the average planning mark and the coefficient of residual soil loosening.

Distribution of earth masses at the site.

After the volume of earthworks has been calculated, they begin to distribute the earth masses. From which site to where to transport the land.

Before that, you need to draw up a balance of earthworks. How many recesses will be, how many embankments.

When distributing earth masses, it is necessary to take into account the profile volume of earthworks and the working volume of earthworks. The worker is larger, he takes into account the slopes.

Distribution of earth masses in a linear structure

Taken into account:

Longitudinal transport of soil;

Transverse transportation of soil.

Which way to accept can be solved using inequality:

S VK + S nr ≤ S ext

С VK - the cost of excavation and laying of soil into the cavalier;

С Нр - the cost of filling in the embankment from the reserve;

With vn - the cost of soil development and filling it into the embankment.

What matters is the correct calculation of the cost of transportation for certain distances.

To correctly determine the length of movement of the soil, the centers of gravity of the embankment and excavation are taken and this will be the average distance for transportation.

General information about machines for earthwork

Soils are developed by mechanical, hydromechanical, explosive, combined and other special methods.

Mechanical method - 80-85% is carried out by this method, by separating the soil by cutting with the help of earth-moving machines (single-bucket and multi-bucket excavators) working for transport or dump, or earth-moving machines: bulldozers, scrapers, graders, graders, elevators and trenchers.

Hydromechanical method - water monitors - they erode the soil, transport and lay or suck the soil from the bottom of the reservoir with dredgers.

Explosive way - based on the use of the force of a blast wave of various explosives laid in specially arranged wells, it is one of the powerful means of mechanizing labor-intensive and heavy work.

Combined method - combines mechanical with hydromechanical or mechanical with explosive.

Special methods - destroy the soil with ultrasound, high-frequency current, thermal installations, etc.

For preparatory work, brush cutters, grubbing machines, rippers, etc. are used.

The soil is transported by dump trucks, caravans, conveyors, railways. transport and hydraulics.

All kinds of rollers, ramming and vibrating machines are used to compact the soil.

Single bucket excavator - self-propelled earth-moving machine of cyclic action; attachments: front shovel, backhoe, dragline, grab, plow and backfill.

In addition, replaceable equipment is used: a crane, a pile driver, a ramming plate, a stump lifter, a concrete breaker, etc.

With a bucket capacity of 0.25; 0.3; 0.4; 0.5; 0.65; 1; 1.25; 2.5; 3; 4.5 m 3 - used in construction, and 40; 50; one hundred; 140 m 3 is used for stripping operations.

The maximum on a construction site is usually 2.5 m 3.

Bucket excavator - self-propelled earth-moving machine of continuous action. There are chain and rotary ones.

Bulldozer - the blade-blade is attached to the tractor. Tractor power 55 - 440 kW (75 to 60 hp).

Bulldozers are used for digging, moving and leveling the ground, as well as cleaning it in pits.

Scrapers - consist of a bucket and a running gear on a pneumatic drive. There are trailed scrapers with a bucket capacity of 2.25 - 15 m 3, self-propelled 4.5 - 60 m 3. Working speed of movement 10 - 35 km / h.

They are used for layer-by-layer digging, transportation and filling with layers of soil. (The cheapest in earthworks).

Road Graders - a self-propelled machine on the frame of which there is a blade with a cutting knife. Designed for planning and grading works with soil.

Graders-elevators - equipped disc plow... They are used for layer-by-layer cutting of soil and moving it to a dump or vehicles.

2. Arrangement of excavations and embankments

Construction of foundation pits

A pit is a recess intended for the construction of a part of a building or structure located below the surface of the earth for the construction of foundations.

Pits are available with vertical walls, with fastenings and with slopes.

According to SNiP, it is allowed to dig pits with vertical walls without fastenings in the ground natural moisture with an undisturbed structure, in the absence of groundwater and the depth of pits in bulk, sandy and gravelly soils no more than 1 m; in sandy loam and loam 1.25 m; in clayey 1.5 m and extra dense 2 m.

Mounts are:

brace anchor sheet pile

But it is better to perform a pit with slopes. The greatest permissible steepness of the slopes of the pits in soils of natural moisture and in the absence of groundwater is taken for excavations

Depth up to 1.5 m from 1: 0.25 to 1: 0;
depth of 1.3 - 3 m from 1: 1 to 1: 0.25;
depth 3 - 5 m from 1: 1.25 to 1: 1.5.

For deeper pits, slopes are calculated.

The development of the pit includes the following working steps:

Development of soil with unloading to the curb or loading into vehicles;

Transporting soil;

Layout of the bottom of the pit;

Backfill with trim and compaction.

Digging a pit is the leading process. The pits are developed using a single-bucket excavator, scraper, bulldozer and hydromechanical method.

Single bucket excavator is used:

During the construction of housing 0.3 - 1 m 3;

In industrial construction, 0.5 - 2.5 m 3, sometimes 4 m 3.

Trenching

Trenches are temporary excavations designed to be laid in them strip foundations or installation of pipelines and cables.

There are 3 types of trenches : with vertical walls, with slopes, and mixed trenches:

Trenches with vertical walls in most require fastening, which means additional consumption of materials, additional labor costs

Without fastening, you can dig from 1 to 2 m, depending on the density of the soil. But it is recommended immediately, to lay pipelines or build a foundation.

In viscous soils, rotary excavators dig up to 3 meters, laying pipelines (gas pipelines, oil pipelines, etc.), fastenings are performed where people descend.

When constructing trenches with slopes, the steepest slope is taken in accordance with the angle of repose and weather conditions.

Mixed trenches are arranged at great depths and the presence of groundwater, the level of which is above the bottom of the trench.

Trench fastenings are:

Horizontal or vertical;

With gaps or solid;

Inventory or non-inventory.

Inventory fences consist of collapsible frames and inventory panels, inventory spacers.

For the development of trenches, single-bucket excavators are used: a backhoe or dragline with a bucket capacity of 0.3 - 1 m 3.

The back shovel can be designed with vertical walls. Dragline with slopes and in the presence of groundwater.

If the trenches are not deep, then the dump is organized next to the trench (lateral or end movement).

If the trench is deep, then the blade is on both sides and the excavator moves in a zigzag pattern.

The bucket excavator is used in the excavation of pipeline trenches.

Operational shift performance of bucket excavator:

c - duration of the shift;

n 1 - the number of unloaded buckets per minute, depends on the speed of movement and the distance between them;

k1 -excavator utilization rate;

k3 -bucket loading factor;

g -bucket capacity.

If the soil in the trench is sorted out, then sand or fine gravel is laid and rammed (but not the soil). When developing trenches for foundations, the soil from under the excavator is usually taken away by dump trucks.

Sometimes in very cramped conditions or when pipelines pass through the road or other obstacles, they dig adits or perform a puncture (trenchless laying).

The fastening of trenches is dismantled from the bottom up, but they can also be left (for example, in quicksand).

Backfilling of trenches is carried out after geodetic survey of laid pipelines or other communications.

Backfill is performed in two stages: first, the pipe is sprinkled on 0.2 m with sand or small gravel, and then everything else with a layer-by-layer compaction.

The device of underwater trenches

Underwater trenches are arranged for laying siphons.

The trench is always developed with slopes, the steepness of which is taken for sandy soils from 1: 1.5 to 1: 3, for sandy sands and loams 1: 1 - 1: 2, for clays 1: 0.5 - 1: 1.
With the width of the development of trenches, the flow rate of the river is taken into account (for small rivers the channel is diverted).

The development of underwater trenches, depending on local conditions, is carried out by an excavator, a rope-scraper installation, dredgers, hydraulic monitors.

In some cases, the trenches are worked by hand.

Subgrade device

The subgrade is the base of the superstructure of highways and railways and consists of embankments and recesses.

The steepness of the slope is taken depending on the type of soil and the height of the embankment.

For non-cohesive soils with an embankment height of up to 6 m, a slope steepness of 1: 1.5 is recommended.

Embankments from 6 m and above should have slopes of a broken profile, more gentle in the lower part.

The process of subgrade construction consists of 2 works : preparatory and basic.

Preparatory - cleaning the track and breaking the road.

Main - development, movement, leveling and soil compaction.

At each section of the roadbed, the soil is worked out by machines of one or several types, which are selected taking into account the conditions of their use and ensuring the highest productivity.

Bulldozers used when making recesses up to 2 m and embankments with a height of 1 - 1.5 m with a movement length of 80 - 100 m.

Scrapers they are used for longitudinal movement of soil from recesses to the embankment at a displacement distance of more than 100 m, and also when embankments from lateral reserves are arranged.

Graders-elevators - it is advisable to use in the construction of low (up to 1 meter) embankments from reserves in the flat terrain. The front of the work of each machine should be within 1.2 - 3 km, the length of the capture is not less than 400 m.

Graders and graders They are mainly intended for leveling and profiling works, they can also be used as the main machines in the construction of subgrade with an embankment height of up to 0.75 m.

Excavators - a straight shovel or dragline is used where the concentrated mass of soil is at least as high as the normal face.

Hydromechanization means they are used if there are natural reservoirs and sources of electricity in the area of \u200b\u200bwork on the construction of the subgrade.

Fastening of slopes of permanent earthworks and banks

During the construction of the subgrade, canals, plumbing and other structures, it is necessary to carry out work on the fastening of slopes and shores.

The soil of slopes and shores is fixed with organic binders (bitumen), grass sowing, protective clothing in the form of a sod, as well as brushwood, stone, reinforced concrete slabs and special protective structures.

A stronger anchorage is paving or stonework in wicker cages ranging in size from 1 x 1 to 1.2 x 1.2 m.

3. Ancillary work in the production of earthworks

Drainage

Excavations in aquifers are developed using open drainage or artificially lowering the level of groundwater.

Drainage is used with a small flow of water.

Disadvantages of Drainage:

Blurs the walls of the grooves;

The influx of water makes it difficult to excavate;

The bottom of the pit is not always dry.

Therefore, they arrange an artificial lowering of the groundwater level.

Water reduction

Lowering the groundwater level is carried out : with the use of light wellpoint installations, providing a single-tiered lowering of the groundwater level to 4 - 5 m, and with a two-tiered one by 7 - 9 m; ejector wellpoints allowing a single-tier lowering of the groundwater level to 15 - 20 m; and tubular wells with deep pumps.

Lightweight needle filter systems consist of a complex of needle filters, an intake manifold and pumps.

The pipes are immersed hydraulically or by drilling. For deep pits, there may be 2 and 3 tiers.

For trenches, it is possible to arrange from one side.

Wellpoints with an ejector device are used to lower the groundwater level in one tier to a depth of 15 - 20 m.

Deep tubular wells carry out a single-tier lowering of groundwater to a depth of 60 m or more.

Submersible pumps are installed in pre-drilled filtered wells (casing pipes) d 200 - 400 mm.

Artesian pumps are also used.

Artificial fencing of excavations from groundwater

Excavations when driving layers with a significant inflow of water can be carried out under the protection of an ice watertight wall of frozen soil or using thixotropic impervious screens.

Artificial soil freezing is used in the development of cuts in quicksand in order to create a temporary waterproof ice wall

Thixotropic screens are made from bentonite clays or from simple clays mixed with cement 1: 2.

Clays absorb water 7 times more than their own mass and, after water saturation, thicken, acquiring water-repellent quality.

4. Features of the arrangement of earthworks in winter conditions

General information

In winter, the soil structure changes: mechanical strength as well as specific resistance to cutting and digging increases sharply (several times).

Therefore, earthworks are very different from summer ones.

But sometimes winter conditions are conducive to earthwork. For example, in swamps, during the development of silty soils, soils saturated with water.

Due to groundwater in the spring, the soil thaws from below. Therefore, at the moment of thawing, the groundwater rises.

The first ice crystals in groundwater appear at t \u003d -0.1 ° C. Soil freezing starts from -6 ° C and below.

In loose soils, sand, sandy loam, water freezes at t \u003d (- 2 ° С - 5 ° С), in clayey soils at t \u003d (- 7 ° С - 10 ° С).

The temperature inside the soil is distributed depending on the depth.

The depth of soil freezing depends on:

Humidity - the higher the humidity, the greater the depth. At a humidity of 30 - 40%, it leads to heaving of the soil;

Groundwater level - the closer the groundwater is to the surface, the less freezing;

The nature of winter and the time of snowfall. The sharper the fluctuations in the outside air, the greater the freezing depth.

The depth of freezing can be determined by the following formula (the soil is not covered with snow):

H - depth of freezing

k - coefficient taking into account the characteristics of the soil:

Clay - 1;

Loam - 1.06;

Sandy loam - 1.08;

Sand - 1.12.

z- the number of winter days before the calculated day.

t- the average outdoor temperature for the period from the beginning of winter to the settlement day.

In addition, the freezing depth can be determined from various graphs and tables. In general, the depth of freezing is determined in nature.

Freezing soil protection

In general, it is difficult to protect the soil from freezing.

The simplest is loosening: harrowing with a depth of 0.15 - 0.2 m, plowing 0.25 - 0.35 m, deep loosening with an excavator up to 1.5 m.

Provide drainage of autumn waters.

Arrange snow retention with a thickness of 0.5 - 1.0 m. For insulation, cover with dry peat, foliage, slag (sawdust is not allowed).

Water-air coating with foam from surface-active substances (SAS), arranged with the help of foam generators with a layer of 30 - 40 cm, reduces the depth of freezing by 10 times.

But soil insulation is advisable only in the first half of winter.

Loosening of frozen soil

When the soil freezes up to 0.1 m, it is developed without loosening.

Frozen the soil is loosened with explosive or mechanically.

The explosive method of loosening is beneficial when the freezing depth is more than 0.8 m (the method is cheap).

The volume is divided into captures, drill holes, lay explosives, explode and develop in the usual way.

Mechanized loosening at a depth of 0.25 - 0.4 m with a ripper or excavator with a bucket of 0.5 - 1 m 3.

If the depth of freezing is 0.5 - 0.7 m and the volume is not large, use free fall hammers, which have the shape of a wedge or a ball, concrete breakers based on a hydraulic excavator.

With a freezing depth of up to 1.3 m, it is better to use a diesel hammer with a wedge.

In addition, frozen soil can be cut into bars into blocks, which are then removed.

A small amount of work is performed with jackhammers.

Thawing frozen ground

This method is used for small volumes of work, usually in cramped conditions.

The soil can be thawed:

Hot water;

Ferry;

Electric shock;

By firing method;

Chemical method (quicklime).

Hot water or steam served through needles placed in pre-drilled holes.

Electric shock - electric needles, electric furnaces, heating elements, coaxial heaters, horizontal or clogged electrodes.

Firing method - burning of any fuel (peat, coal, firewood, wood chips, diesel fuel, etc.) under a metal box or pipe.

Excavation, backfill and embankment

In winter, the soil is developed in the usual way.

The development of the soil is carried out sequentially, quickly and lay the foundation while the soil is warm.

Shallow trenches (up to 1.5 m deep) under the foundations are insulated.

backfilling It is made in compliance with the following requirements: when filling in the sinuses of foundation pits and trenches, frozen clods should not exceed 15% of the volume of backfill; inside the building, it is covered only with thawed soil.

Pipelines for 0.5 m are covered with thawed soil.

Above, you can fill it with frozen soil that does not contain clods larger than 5-10 cm.

Construction of roadbed embankments in winter conditions: when constructing a road embankment, up to 20% of frozen soil is allowed, a railway embankment - up to 30%.

Clay soils in the embankment should be no more than 4.5 m.

The upper layer of the embankment is thawed soil 1 m thick.

When planning the site, up to 60% of frozen soil is allowed.

The base for foundations can be taken over frozen, but not in heaving soils.

5. Organization of a complex mechanized process of erection of earthworks

With comprehensive mechanization, all earthwork processes are performed mechanically: loosening, soil development, soil transportation, leveling, compaction.

The leading machine is selected, which is to be used most fully.

The rest of the set of cars is picked up to her.

The cost of 1 m 3 of the processed soil is determined and the set of machines is compared with another set.

With - unit costs per 1 m 3

From 0 - total cost of earthwork

V - overall volume

With m.sm. - the cost of machine changes in rubles.

T - the duration of the operation of the machine at this facility

C d - additional expenses associated with the organization of the production of earthwork, rubles (arrangement of roads, maintenance of roads, etc.)

3 - the salary of workers not included in the cost of machinery.

6. Quality control of earthworks and their acceptance

It is necessary to systematically check the performance of the design documentation and the requirements of SNiP 3.02.01-87 "Earthworks, foundations and foundations".

It is necessary to keep a journal of works that reflects the properties of the soil (plasticity, humidity, viscosity, etc.).

After the excavation is made, a tripartite act is drawn up (customer, contractor, geologist or designer) on the conformity of the base to the project for the possibility of further work.

When handing over earthen structures, the contractor must submit to the commission executive drawings, in which all changes, deviations from the project, acts hidden works, acts of soil testing, acts of geodetic surveys.

Grading. In practice, the nature and quality of rock destruction is clearly determined by its granulometric composition. It characterizes the loosened rock in terms of the percentage of particles of various sizes in it and can be depicted by a curve (Fig.2.1), if the abscissa axis is the particle diameter, mm, and the ordinate is the total content of particles with a diameter smaller than this, in percent.
To characterize the heterogeneity of loose rocks, the ratio d60 / d10 \u003d Kн is used, which is called the heterogeneity coefficient (d60, d10 are the maximum diameters of pieces that make up 60 and 10% of the total volume of loose rock, respectively).
Particularly important is the granulometric composition of the rock in the processes of hydromechanization. The specific water consumption for development and transportation, the smallest permissible slope of the bottom of the face and trays, and the critical water velocity depend on it.
The angle of repose φ is the maximum angle formed by the free surface of loose crushed rock with a horizontal plane. The rock particles located on this surface experience a state of ultimate equilibrium. If the weight of the particle is P (Fig. 2.2), then in the state of limiting equilibrium on the free surface the following forces act on the particle: Pn is the force of normal pressure, which presses the particle to the free surface; Рτ - force tending to move the particle down; Fт - friction force, depending on Рn and coefficient of friction fтр, R - support reaction. Since the particle is in equilibrium, we have

i.e.

When building foundations or laying communications in the ground, it is required to dig ditches and trenches. Earthworks must be accompanied by safety measures. They define the rules for securing the sides and bottom. To determine the slope of the pit, use the table. Its application allows for the soil at the construction site to select the desired level of inclination of the walls of the dug recess to its bottom so that collapse does not occur.

Types of earthworks

The construction of buildings and communication facilities is associated with labor-intensive earthworks. They mean the development of soil when digging pits and trenches, its transportation, storage.

Earthen structures are embankments, excavations. They can be of a permanent type or temporary. The first ones are made for long-term operation. These include:

• channels;
• dams;
• reservoirs;
• dams and other structures.

Temporary excavations are trenches and pits. They are intended for subsequent construction work.

A pit is a recess, the width and length of which practically do not differ significantly in size. They are necessary for the construction of foundations for buildings.

The trench is a long furrow compared to its cross section. It is intended for the installation of communication systems.

According to the requirements of GOST 23407-78, digging of pits, trenches in settlements, places of traffic, or people, must be accompanied by the creation of protective fences. They are installed around the perimeter of the work area. They are equipped with warning signs and inscriptions, and even signal lighting is used at night. Also specially equipped bridges for the movement of people.

Slopes are sloped sidewalls of cut or fill. An important characteristic their is bias (steepness). The horizontal slopes surrounding the slopes are called berm.

Under the bottom of the recess understand its lower, flat part. The brow is the top edge of the created slope and the sole is the bottom.

When operating earthworks, they must not:

• change their shape and linear dimensions;
• sit down;
• eroded by water or succumb to rain.

Laying water pipelines, underground power lines, sewerage systems, building foundations for buildings cannot do without digging trenches or foundation pits. In construction, special definitions have been adopted to designate structural elements of this type. All work must be carried out in strict compliance with safety rules in order to minimize the possibility of accidents.

Varieties of pits

Digging recesses for the base of a structure is a responsible business that requires a lot of time, money, and labor. It is customary to divide pits today according to the following criteria:

• the presence of slopes;
• the use of fasteners designed to prevent soil screes;
• type of side surfaces (walls).

The walls of the pits can be:

• vertical
• inclined;

• stepped.

In order to carry out earthwork correctly, first conduct research on the construction site. These activities include the following operations:

• analysis of soil properties: establishing its group and type;
• determination of loads from the building being erected;
• calculation of the depth of the excavation;
• establishing the presence of old communications;
• determination of the depth of groundwater;
• analysis of weather conditions of the area.

The choice of the method of work is determined depending on the following factors:

• type and dimensions of the structure being built;
• the depth of the foundation;
• volume of upcoming activities.

If it is planned to build a shallow base of a tape or columnar type, then the soil can be developed without involving equipment, manually. When it is necessary to build a house with a basement, or a basement, then earth-moving mechanisms will need to be involved in the work.

To extract the bulk of the soil from the excavation, excavators of various types are often used, equipped with a backward or forward shovel. Work associated with digging a foundation pit should be performed without disturbing the density of the soil at the bottom of the foundation. This requirement is implemented in practice through its shortage, the value of which ranges from 5 to 20 cm.

Cleaning of the earth from the sides and from the bottom of the excavation to the planned mark is done manually by workers. In this case, it is imperative to monitor the strengthening of its walls with the help of slopes, or through the installation of special structures. The fallout of precipitation and the rise of groundwater in spring and summer, the impact of frost in winter - all this contributes to the destruction of the pit.

The soil from the pit must be immediately removed or placed on the construction site no closer than 1 m from its edge. A drainage system is created to drain the soil water.

An important point when digging pits is the creation of a working space of the sizes required according to the rules. It should take at least half a meter from the foundation formwork to the bottom of the slope. The steepness of the slopes of the pit is selected according to the tables or graphs given in SNiP 3.02.01-87.

Types and purpose of trenches

Laying under various communications of trenches is the most common type of earthwork. Their manual digging is slow and expensive, so they often use the equipment they buy or rent.

According to the purpose, excavations of this type are divided into the following types:

• for grounding;
• plumbing;
• cable;
• gas pipelines;
• drainage (drainage);
• sewer.

By design, trenches are of 3 types:

• rectangular;
• trapezoidal;
• mixed.

Spacers are installed inside trenches without sidewall slopes to increase safety for people. Strengthening the slopes is not required, because they are made to protect against collapses. Trenches designed for laying communications, digging out various depths using different techniques.

Soil: groups and types

Due to the fact that earthen structures are created in soils, it is imperative to know their main characteristics. The suitable type of foundation directly depends on them. The choice is made taking into account the achievement of the highest possible level of reliability and durability of the erected base.

The main properties of the soil are determined by the following factors:

• shape, size, strength, arrangement of particles that make up its composition;
• the degree of interconnection between them;
• the ability of the constituent substances to solubility, moisture absorption.

The soil is characterized using such coefficients:

• compressibility;
• friction;
• plasticity;
• loosening.

The classification provides for the division of soils according to various criteria. There are the following types:

• sandy;
• dusty;
• clayey;
• rocky;
• clastic.

Depending on the water content, soil is released:

• dry (up to 5% moisture present);
• wet (5-30%);
• wet (contains more than 30% water).

The division into groups is presented in the table below.

• quicksand;
• soft
• medium;
• strong.

The structure and properties of the soil at the construction site play a major role in the calculations during the design of the foundation. This is due to the fact that depending on the type of soil is its bearing capacity. Also, each species reacts differently to weather conditions.

Excavation plan, requirements for them

Excavation is carried out in a number of stages. They are prescribed in SNiP 3.02.01-87. The main stages of the process are as follows:

• implementation of preparatory activities;
• experimental and production part;
• creation of a pit or trench;
• carrying out control measures;
• acceptance of work performed.

SNiP 3.02.01-87 provides for the following requirements:

• to develop a working draft is allowed only by specialists who have the necessary qualifications, experience;
• communication and coordination of actions in matters of design, construction, engineering solutions should be ensured between them;
• it is constantly necessary to control the quality of construction work on the site;
• the project must be carried out by appropriately qualified personnel;
• the erected structure is allowed to be used only for the purpose in accordance with the project;
• activities for maintenance structures and associated engineering communications must maintain it in a safe, working condition during the entire operation.

When digging pits and trenches, you must adhere to the instructions:

• rules for organizing their construction;
• norms for conducting geodetic works;
• labor protection standards;
• rule sections fire safetyconcerning the construction work.

Earthworks should be created strictly according to the current project.

Explosive work requires compliance with the relevant safety rules during their production.

The materials, structures, products used in the work must meet the requirements of the standards and the project. Their replacement is allowed only after prior agreement with the organization that developed the documentation, the customer.

There are the following types of control during excavation work:

• input;
• operating;
• acceptance.

Control is carried out in accordance with SP 48.13330.

Acceptance of work takes place with the preparation of the necessary documentation (acts) confirming their implementation.

The considered requirements in individual construction are greatly simplified. Small buildings are often erected without any projects, and the depth of the excavations does not exceed 1.5-2 m, but safety precautions must always be observed.

Safety measures when digging pits

Soil from the side walls of the pit or trench as a result of the action of gravity on them can move and fill the bottom of the excavation. Due to uncontrolled collapse of the earth masses, accidents with people are possible. Also, destruction leads to an increase in labor costs and means: it will be necessary to restore the planned contour of the excavation, to backfill the base with a large amount of soil.

To prevent shedding and reduce the possibility of material losses to a minimum, it is necessary to correctly calculate, at the design stage, according to SNiP 111-4-80, the steepness of the slopes of the excavation being created.

If the depth of the trench or pit, on average, exceeds 1.25 meters, then it is necessary to strengthen their walls in order to prevent possible collapse, earth slides. Along the contour of the dug structures, strips should remain free from the excavated ground mass, the minimum width of which is more than 0.6 m. The ground from the excavation should not roll back.

The parameters of the side slopes before excavating the pit must be determined correctly. This will allow:

• prevent the possibility of collapse;
• perform the optimal amount of earthwork;
• will save you from the cost of reworking slopes during construction work.

Landslide prevention is the main task of ensuring safety for personnel.

Compliance of the slopes with the optimal slope angles for a given type of soil minimizes the money and labor costs for backfilling and reworking.

Before starting work, geological and hydrological surveys of the development site are carried out. In the presence of soil water, unstable soils, or if it is necessary to dig an excavation more than 5 m deep, a project is created for the identified individual conditions.

According to SNiP 111-4-80, for non-moist soils with a uniform structure, it is possible to leave vertical ones when digging trenches or pits side walls. At the same time, there should be no structures near the excavations and groundwater. The permissible excavation depth for different soils with vertical walls is for:

• gravel, sandy - 1 m;
• sandy loam - 1.25 m;
• clay and loamy - no more than 1.5 m;
• highly dense - 2 m.

In pits with a depth of about 1.25 m, it is required to use stepladders that will rise above the ground to a height of at least 1 m. In deeper excavations, staircases are used.

The side surfaces of the pits are allowed to be strengthened with edging. If possible additional loads, or washing out the slopes, they are covered with a film or shotcrete (concreting with a thin layer).

Slope table

When you need to dig a hole from 1.5 m deep, then you should take the angle of the pit slope according to the table given in SNiP 111-4-80. It takes into account both the type of soil and the depth of the foundation.

In the construction literature, standards, and rules, the steepness of a slope of a excavation is measured in degrees (angle), or by the ratio of its height to the laying.

A table of the steepness of the slopes for pits of different depths and on different types of soil is presented below.

Despite the presence of slopes, there remains the possibility of collapse of the ground mass under the influence of the weight of the involved equipment. Therefore, the distance from the parking of cars to their soles is also regulated by SNiP.

When different types of soil are present at the construction site, then the steepness of the slopes is chosen according to its most unstable variety.
It is recommended to remove existing inclusions of boulders and stones with the help of an excavator to prevent the possibility of landslides and collapses.

The walls of the recesses up to 3 m deep are fixed in accordance with the design guidelines.

If the soil connectivity changes for the worse in the working area when water gets into it, during drying, under the influence of low temperatures, then it is recommended to equip slopes of less steepness, or with indents.

When the side surfaces of the pits up to 3 m deep are formed with steps, the width of the latter should be at least 1.5 m. In this case, the slopes should also be made.

If the design depth of the excavation exceeds 5 m, or the steepness of the pit wall is different from the tabulated value, then the stability of the slopes must be calculated.

Pits, or trenches dug in autumn or winter frosts, must be inspected during the spring thaws and determine the stability of their slopes.

With the slope angles considered in the table for each type of soil and the depth of the pit, workers can be in the excavation without the need to fix the slopes. If the slopes were wetted, then before starting work, they are inspected for cracks, delaminations.

Excavation methods, used mechanisms

Depending on the soil, it is used in the arrangement of trenches and pits different technique, various methods of development of plots for construction are applied. They differ in the complexity and level of required material costs. According to SNiP 111-4-80, the following methods are distinguished:

• hydromechanical;
• mechanical;
• blasting operations.

The mechanical method of excavating pits and trenches is the main one. Its essence lies in digging soil using earth-moving (excavators) machines, or earth-moving transport (scrapers, bulldozers, graders).

The hydromechanical method is based on the erosion of the soil mass by a jet of water from a water jet. Then the resulting solution is sucked by a dredger.

Blasting works are mainly used in suburban construction. Holes (wells) are drilled in the ground. Then explosives are placed in them and detonated. The resulting loose mass is taken out with the help of technology.

The mechanical method consists of a number of steps:

• loosening the soil;
• mining of rock;
• its transportation;
• alignment, compaction of side slopes and bottom.

Hydromechanical excavation works are carried out in the following sequence:

• designate with the help of fences, inscriptions, warning signs the area of \u200b\u200bthe working area;
• according to the norms, a hydraulic monitor is set that is manually controlled by the operator: the distance from its nozzle to the pit wall should be no less than the height of the excavation, and at least two intervals to which the water jet can be supplied by this technique to the nearest overhead power line;
• slurry pipelines and water conduits are placed outside the security perimeter of power lines;
• enclose places of dumps of reclaimed earth mass;
• erosion and excavation are performed.

Do not operate the jet monitor during a thunderstorm.

Blasting is regulated by the relevant rules.

When mechanical loosening of the earth mass is carried out by the shock method, then the workers should not be within a radius of 5 m from the place of loosening.

Any equipment must be positioned during work in accordance with applicable standards and rules. Departure from them often leads to accidents.

Soil consolidation technologies

Depending on geological characteristics building plot and climatic features of the area, the depth of the excavation, the features of the constructed or reconstructed buildings in practice are used various ways consolidation of soils. Technologies can improve them in terms of resistance to destruction. In SNiP111-4-80 the following methods of consolidation are distinguished:

• thermal;
• cement;
• using cement mortar.

Very often used different kinds mechanical fasteners. By design, the following types are distinguished:

• braced;
• cantilever-spacer;
• spacer;
• cantilever-anchor;
• cantilever.

The choice of the type of fastening is made on the basis of the above factors that affect the correct conduct of work.

According to the design and the possibility of quick installation and dismantling, the following types of fasteners are distinguished:

• stationary;
• inventory;
• at intervals;
• solid.

The upper part of the fasteners after their installation should rise above the edge of the pit or trench by more than 0.15 m. In this case, the installation itself is performed from top to bottom during excavation of earth masses, and disassembly in the opposite direction when backfilling.

The spacer type of fasteners is most widespread. Use this option if the depth of the trench does not exceed 3 m. The structure consists of the following elements:

• shields;
• screw spacers or frames;
• racks.

The fixing of the side surfaces of the trenches is carried out immediately after fragments thereof.

On weak, wet soils, console-spacer or console types of fasteners are used. In this case, the depth of the grooves should be within 3 m.

A variety of cantilever mounts are sheet pile. They fix the walls of deep pits, where there is a lot of pressure from the sides and difficult hydrogeological conditions.

Braces are rarely used because they make work difficult.

The fixing method is determined by the project documentation. If you need these measures during individual development, you can rent various fasteners, or make metal or wooden analogues of factory products yourself. Determining the choice in favor of one or another option of fasteners is required depending on the conditions at the construction site.

The videos below show the various methods of securing the soil on the slopes of the pit.


The process of forming a slope with an excavator is demonstrated in the following videos.


Giving stability to the side surfaces of the pits is the first requirement that is presented when creating them. In order to ensure safe working conditions, prevent talus and comply with construction technology, excavations with slopes of the required steepness are being erected.

If the depth of the pit does not exceed 1 m, then on any type of soil, the slope on the side surfaces is not made, and for hard rocks, vertical walls of the excavation are left even at depths of up to 2 m.The slopes of the pits are formed according to the SNiP tables, if the depth is up to 5 m.After exceeding of this value - perform special calculations.