Natural sand slope. Determination of the angle of repose of sandy soil

REPUBLICAN BUILDING CODES

ENGINEERING SURVEYS FOR CONSTRUCTION.
PRODUCTION OF LABORATORY RESEARCH
PHYSICAL AND MECHANICAL PROPERTIES OF SOILS

RSN 51-84

Gosstroy RSFSR

RSFSR STATE COMMITTEE ON AFFAIRS
CONSTRUCTION

Developed by the trusts of engineering and construction surveys MosTsTISIZ, UralTISIZ, TulaTISIZ of the Production Association for Engineering and Construction Surveys ("Stroyiziskaniya") of the State Construction Committee of the RSFSR.

Performers: I.N. Shishelov, Ph.D. those. Sciences Yu.V. Syrokomsky, I.B. Kogos, T.D. Beloglazova, R.A. Menshikova, L.I. Podkorytova, A.S. Romanova.

Submitted and prepared for approval Production Association for engineering and construction surveys (“Stroyiziskaniya”) of the State Construction Committee of the RSFSR.

Introduced for the first time.

These Republican building standards apply to organizations performing soil studies during engineering surveys for the construction of industrial, residential, civil and agricultural facilities and establish the basic requirements for laboratory studies of the physical and mechanical properties of soils.

1. GENERAL PROVISIONS

1.1. Laboratory soil tests should be carried out in accordance with the requirements state standards, building codes and rules, as well as these Republican building codes.

1.2. The composition of laboratory soil tests must be established in accordance with the requirements of current regulatory documents and programs for survey work.

1.3. Laboratory studies of soils should be carried out using progressive methods, modern instruments and equipment that ensure high quality soil testing, highest labor productivity and reduced duration of laboratory work.

1.4. When carrying out laboratory soil studies, measures should be taken to save materials and electricity, as well as ensure careful handling of equipment, instruments, tools and inventory.

1.5. The cost of laboratory work is determined according to the Collection of prices for survey work for capital construction.

1.6. When carrying out laboratory work, it is necessary to comply with the requirements stipulated by the rules and instructions on labor protection and safety.

2. ORGANIZATION OF LABORATORY WORK

2.1. Laboratory works should be carried out in accordance with the schedule and tasks for their implementation.

The schedule is drawn up by the head of the laboratory and agreed upon with the head of engineering and geological production departments - customers of laboratory soil studies.

Back an e on laboratory and soil investigations is compiled customer department these x works. The assignment must be signed by the head of the department and the chief geologist m production customer department.

2.2. Quality control of laboratory soil studies - input, operational, acceptance - should be carried out in accordance with the enterprise standard of an integrated quality management system for engineering surveys in construction (K SUKIIS) at all stages of work.

Input control should be carried out on soil samples received for research, customer orders, and newly received equipment, instruments, and instruments. Incoming control must be continuous and carried out by the head of the laboratory and or a specially authorized employee.

Operation and this control should be carried out in the process of conducting laboratory studies of soils and maintaining primary documentation. The following work processes are subject to special control: taking an average sample, cutting out soil samples, maintaining the temperature at a certain humidity, periodic calibration of the hydrometer when determining granulometric composition, calculation of loads when determining shear resistance.

Op Rational control of devices should be carried out in accordance with the requirements. Performers must carry out continuous operational control (self-control), the head of the laboratory or a specially authorized employee is selective.

At The results of laboratory soil tests, prepared for transfer to the customer, should be subjected to strict control. Acceptance control must be continuous and carried out head of the laboratory.

2.3. Re The results of laboratory and soil research are provided to the customer in the form machine-oriented statements when processing data on a computer or in the form of statements of passports of results and soil investigations.

2.4. Inform The head of the laboratory immediately transmits information about deviations from the standards during laboratory soil studies to the customer of the laboratory work.

3. EQUIPMENT, DEVICES, PREMISES

3. 1. Laboratory and soil research must be provided with equipment, instruments, tools and supplies in accordance with the equipment sheets from survey and research equipment design and survey organizations devices, equipment m, vehicles, camp equipment and communications equipment.

3.2. For metrological assurance of laboratory research of the physical and mechanical properties of soils, the equipment and instruments of the soil laboratory must be tested within the prescribed time frame in accordance with the requirements of GOST 8.002-71 and the standards of the KSUKIIS enterprise.

3.3. To ensure constant operational readiness of equipment and devices, the system should be applied in a planned manner. - warning repairs, providing for complex x precautionary measures aimed at eliminating progressive purl wasps.

3. 4. Maintenance, providing supervision, care, checking the condition of equipment and devices, with the exception of electrical equipment, should be carried out co to the new schedule by the staff py ntova laboratories - preparators, laboratory assistants, technicians and engineers.

3 .5. Routine repair of equipment and devices, providing for the replacement or restoration of parts and assemblies, troubleshooting operations, and maintenance of electrical equipment must be carried out by a mechanical repair service from a survey organization.

3.6. In the premises of the research laboratory soil equipment should be grouped based on the need for it to work together, as well as on the principle of equal impact on environment(emission of dust, heat, vapors; noise, etc.) and environmental influences (vibration, temperature, humidity).

3.7. The composition of laboratory premises and soil research is established depending on the composition, properties, and condition of soils; composition and quantity of equipment. The minimum and maximum compositions of premises are given in.

3.6. The sequence of location of the premises is established according to the routes of soil movement according to the analyzes.

3.9. The area of ​​the premises is determined depending on the composition and quantity of equipment, the size of the passages between the equipment, and the number of employees.

3.10. Special requirements The planning of soil research laboratories is given in .

3.11. Special requirements for water supply, sewerage, ventilation, and power supply for the soil research laboratory are given in.

4. STORAGE, TRANSPORTATION AND PREPARATION OF SOIL SAMPLES FOR ANALYSIS

4.1. Acceptance and storage soil samples in the laboratory Soil studies should be carried out in accordance with with the requirements of GOST 12071-72.

To the customer department With le blows d leave and lay out and the shelves stored laboratory samples in the order in which he and outside the hay in the task.

N ach alni ku l laboratories and li spe cially authorized employee in in the presence of a geologist in charge of the object, the safety of the samples should be checked, no mechanical damage packaging, sufficiency and suitability of samples for production provided for by specifying the composition of the definitions.

4.2. Horizontal transportation soil in the laboratory premises should be carried out using manual transport trolleys, vertical transport - freight elevators or special lifts.

4.3. Study physical and mechanical properties of soils when opened samples should be start with visual examination and description of samples. The description should contain information about the composition , lithological especially nn ostya x and condition of the samples.

4.4. Cutting samples and preparing soils for analyzes should be carried out usually with the help of mechanisms.

5. METHODS OF SOIL STUDY

5.1. Soil classification should be carried out in accordance with the requirements of GOST 25100-82.

5.2. Granulometric and microaggregate composition should be determined in accordance with the requirements of GOST 12536-79. Screening soils should be produced using mechanical systems, shaking - using a mechanical agitator.

5.3 . Density should be determined in accordance with the requirements of GOST 5180 - 75.

5.4. Soil density should be determined in accordance with the requirements of GOST 5182-78. The density of soil in loose and dense states should be determined in accordance with the requirements.

5.5. The density of soil particles should be determined in accordance with the requirements of GOST 5181-78.

5.6. The density of rock particles should be determined in accordance with the requirements.

5.7. The limits of yield and rolling should be determined in accordance with the requirements of GOST 5183-77.

5.8. When determining the yield boundary, mechanized methods of lowering the cone (without additional force) and automated methods of counting experimental time intervals should be used.

5.9. The maximum molecular moisture capacity should be determined in accordance with the requirements.

5.10. Swelling and shrinkage characteristics should be determined in accordance with the requirements of GOST 24143-80.

5.11. Soakability should be determined in accordance with the requirements.

5.12. Subsidence characteristics should be determined in accordance with the requirements of GOST 23161-78.

5.13. Resistivity penetration should be determined in accordance with the requirements.

5.14. The maximum density should be determined in accordance with the requirements of GOST 22733-77. A mechanized method of lifting the load and an automated method of turning off the device after a cycle of impacts should be used.

The angle of repose should be determined in accordance with the requirements.

The filtration coefficient should be determined in accordance with the requirements of GOST 25584-83. Automated methods should be used to count the time when the liquid decreases by a given amount.

5.17. Suffusion compressibility should be determined according to GOST 25585-83.

5.18. Compressibility should be determined in accordance with the requirements of GOST 23908-79.

5.19. The compressibility of eluvial soils should be determined in accordance with the requirements.

5.20. Shear resistance should be determined in accordance with the requirements of GOST 12248-78. In devices with a constant cutting speed, mechanized devices for moving the carriage and automated means of fixing the maximum force of the dynamometer in the sample deformation area of ​​0-5 mm and turning off the device when the deformation reaches 5 mm should be used.

5.21. Ultimate strength of rocky soils from reduced to very low strength under uniaxial compression of samples correct form should be determined in accordance with the requirements of GOST 17245-79.

5.22. The tensile strength of rocky soils from very strong to low strength under uniaxial compression of samples from the right company should be determined in accordance with the requirements of GOST 21153.0-75 * and GOST 21153.2 -75.

5.23. Ultimate strength of rock soil samples free form should be determined in accordance with the requirements of GOST 21941-81.

5.24. The weathering coefficient should be determined in accordance with the requirements.

5.25. Corrosive activity should be determined in accordance with the requirements of GOST 9.015-74.

5 .26. The relative content of plant residues and the degree of decomposition of peat soils should be determined in accordance with requirements GOST 23740-79.

6. LABORATORY DOCUMENTATION

6.1. workers Logbooks, output statements, passports and other laboratory documents should be prepared in accordance with the requirements state standards and “Manuals for the preparation and execution of documentation of engineering surveys for construction.”

6.2. Ter Mines and definitions used in laboratory documentation must correspond to those given in the state standard.

6.3. Units and units of physical quantities, the name and designation of these units used in laboratory documentation must correspond to the units given in GOST 8.417-81 and in CH 528-80.

OPERATIONAL CONTROL OF DEVICES

This control method applies to: balancing cone, sieves, scales, compression and shear devices, pre-compaction devices. A general control requirement is external inspection. It is established that there are no bends, dents, nicks, or soil particles on the device parts. Control is divided into shift and quarterly. For each device, the first subclause of this methodology contains the requirements for shift monitoring, and the second – quarterly monitoring. Devices that do not meet the requirements of the methodology are not allowed for use.

1. Balance cone

The tip of the cone should not be blunt.

Measure with a depth gauge (vernier caliper) the distance from the top to the base of the cone (25 mm) with an accuracy of 0.1 mm. Check the readings with those obtained when putting the cone into operation. The discrepancy between readings should not exceed 0.2 mm. The cone must be firmly connected to the arc, and the arc to the weights.

2. Sieves for sifting soils

Examine the sieve meshes to light. The meshes should not have any irregularities in weaving, displacement or breakage of wires, or breaks at the points of attachment to the body.

View under a microscope with a forty-fold magnification of a sieve No. 0.1; 0.25; 0.5 in five places along the radius of the sieve. The holes should be square in shape. Determine the size of the holes using the Huygen eyepiece scale. The results should not differ from the nominal values ​​by more than 20%.

Determine the dimensions 5 holes in sieves No. 1 and 2 along the radius of each sieve. Using a caliper, measure five holes along the radius of each sieves No. 5 and 10. The sizes of the mesh holes should not differ from the nominal ones by more than 10%.

Press your hand sequentially on the hoop, the drilled screen disk, and the bottom disk. Parts should not wobble when pressed.

3. Quadrant laboratory scales

3.1. Check the position of the air bubble on the scale level. Move the bubble to the center of the control circle by rotating the legs of the scale.

Align the zero mark on the scale with the zero mark on the screen. Place a standard weight on the scale, the mass of which corresponds to the mass measurement range on the scale. Repeat the operations until the required weighing limit is reached. The difference in readings should not exceed the permissible weighing error.

3.2. Check the clarity of the scale image on the screen, achieve clarity by moving the scale illumination lamp.

4. Compression device

4.1. When preparing the device for the experiment, hold the bottom and stamp to the light. All openings must allow light to pass through.

The compression mechanism ropes must lie in the machined grooves.

3.5. It is allowed to use air-dry soils adjusted for hygroscopic humidity in accordance with GOST 5181-78.

3 .6. Distilled water is boiled for 1 hour and stored in a sealed bottle.

3.7. Compile a table of masses of pycnometers with distilled water at various temperatures. The masses of pycnometers with distilled water at different temperatures are calculated according to GOST 5181-78.

4. Carrying out the test

Complies with GOST 5181-78.

5. Processing the results

Complies with GOST 5181-78.

ME TOD OPR DIVISION OF MAXIMUM MOLECULAR MOISTURE CAPACITY

Infusion This technique applies to silty-clayey and sandy soils and establishes a method for laboratory determination of the maximum molecular moisture capacity.

1. General provisions

1.1. The molecular moisture capacity of soil is the ability of soil particles to hold this or that amount of water on their surface by molecular attraction.

1.2. The maximum molecular moisture capacity should be determined as the moisture content of the soil paste after pressing it until the soil loses water.

1.3. The maximum molecular moisture capacity of silty clay soils is determined using samples with natural moisture.

1.4. The determination of the maximum molecular moisture capacity is carried out with two repetitions.

2. Equipment

1.4. Weighings are carried out with precision ± 1 g

1.5. Calculation results To VK must have an error of no more than 0.01.

2. Equipment

Shelf drum with a rotation speed of 50-70 rpm.

Sieve with mesh No. 2 according to GOST 3584-73 with a tray.

Laboratory scales with a weighing limit of 5 kg according to GOST 19491-74.

3. Preparation for testing

3.1. Take an average sample weighing 2-2.5 kg, avoiding “round” values ​​of 2 or 2.5 kg.

3.2. The soil is separated into fine earth and debris by sifting through sieve No. 2.

3.3. Set the mass of fine earth T 1 and debris T 2 .

4. Testing

4.1. The sample is loaded into the shelf drum.

4.2. Tests are carried out in cycles of drum rotation for 2 minutes, each time establishing the mass of fine earth by sifting; the natural degree of destruction is taken to be the ratio t 1 to t 2 after a four-minute test in the drum.

4.6. If the yield of fine earth increases by more than 25% per TO take the value established before the start of the test.

4.7. The obtained values ​​of the masses of fine earth and debris, corresponding to various cycles, are recorded in a log.

5. Processing of results

5.1. TO calculated using the formula ( ).

5.2. Name of coarse soils according to the degree of weathering depending on To VK given in table. 1.

Table 1

Name of coarse soils according to the degree of weathering

General provisions

Purpose and types of earthworks

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

The following main types of earthworks are distinguished::

Site layout;

pits and trenches;

Roadbeds;

Dams;

Channels, etc.

Earthen structures are divided into:

Permanent;

Temporary.

Permanent ones include pits, trenches, embankments, and excavations.

There are requirements for permanent earthworks:

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

Sustainable;

Good resistance to atmospheric influences;

Good resistance to erosion;

Must be sediment-free.

Basic construction properties and classification of soils

Soil is the rock that lies in upper layers earth's crust. These include: plant soil, sand, sandy loam, gravel, clay, loess-like loam, peat, various rocky soils and quicksand.

Based on the size of mineral particles and their mutual connection, the following soils are distinguished: :

Cohesive – clayey;

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

Rock – igneous, metamorphic and sedimentary rocks with rigid connections between grains.

The main properties of soils that influence production technology, labor intensity and cost of excavation work include:

Volumetric mass;

Humidity;

Blurability

Clutch;

Looseness;

Angle of repose;

Volumetric mass is the mass of 1 m3 of soil in its natural state in a dense body.

The volumetric mass of sandy and clayey soils is 1.5 - 2 t/m3, rocky soils that are not loosened up to 3 t/m3.

Humidity - the degree of saturation of soil pores with water

g b – g c – mass of soil before and after drying.



When humidity is up to 5%, soils are called dry. With a humidity of 5 to 15%, soils are called low-moisture soils. When the humidity is from 15 to 30%, the soils are called wet.
When the humidity is more than 30%, the soils are called wet.

Cohesion is the initial shear resistance of soil.

Soil adhesion force: - sandy soils 0.03 – 0.05 MP; clay soils 0.05 – 0.3 MP; semi-rocky soils 0.3 – 4 MPa; rocky soils more than 4 MPa.

IN frozen soils the adhesion force is much greater.

Loosening ability– this is the ability of soil to increase in volume during development, due to the loss of connection between particles. The increase in soil volume is characterized by the loosening coefficient K r. After compaction, the loosened soil is called residual loosening K or.

Angle of repose characterized physical properties soil. The magnitude 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 equal to angle 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 foundation m – slope coefficient.

Angles of natural repose of soils and the ratio of slope height to foundation

Soils The value of the angles of natural repose and the ratio of the height of the slope to its foundation at different soil moisture levels
Dry Wet Wet
Angle in degrees Angle in degrees Height to lay ratio Angle in degrees Height to lay ratio
Clay 1: 1 1: 1,5 1: 3,75
Medium loam 1: 0,75 1: 1,25 1: 1,75
Light loam 1: 1,25 1: 1,75 1: 2,75
Fine sand 1: 2,25 1: 1,75 1: 2,75
Sand medium-grained 1: 2 1: 1,5 1: 2,25
Coarse sand 1: 1,75 1: 1,6 1: 2
Vegetable soil 1: 1,25 1: 1,5 1: 2,25
Bulk soil 1: 1,5 1: 1 1: 2
Gravel 1: 1,25 1: 1,25 1: 1,5
Pebbles 1: 1,5 1: 1 1: 2,25

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

Laboratory work 1. Determination of the magnitude of the pouring angle and the angle of repose of granular-lumpy material

Goal of the work.Determine the values ​​of the angle of repose and the angle of pouring of granular-lumpy material.

Theoretical provisions . Granular-lumpy material lying on an inclined plane (for example, on an inclined plane of a bunker, on an inclined belt conveyor, etc.), at a certain angle of inclination of this plane to the horizon, begins to pour down it. This maximum angle of inclination is called the pouring angle.

Depending on the shape of the pieces, two types of movement of the piece of material along the pouring plane can be observed: sliding and rolling. Sliding is observed in pieces with developed flat edges; the movement of the pieces here is prevented by sliding friction between the edges of the pieces and the plane of the pouring. Rolling is observed when the pieces are shaped close to a ball. In this case, the movement of the piece occurs as it rolls, with rolling friction resistance.

The limiting state of rest of a layer of lump material on an inclined plane occurs when the friction force F equal to the projection M gravity G to this plane (Figure 1). On the other hand, the same friction force is proportional to the normal pressure of the piece of material on the inclined plane

F= M= fN,

whence f = M / N = tanα

Where f –friction coefficient, determined by the properties of the material itself, equal to tga ;

α – angle of pouring of granular-lumpy material.

Picture 1

If we consider the entire layer of bulk material that moves along a smooth inclined plane, then here, even in the case of spherical pieces, the material slides along the plane rather than rolling, since the entire material “flows” as a continuous mass.


The pouring angle depends on the coefficient of friction of the material on the pouring plane, on the shape and size of the pieces, on the structure of the surface on which the pouring occurs (the surface can be smooth, rough, ribbed, etc.), as well as the moisture content of the piece of material itself.

If you pour granular-lumpy material onto a horizontal plane, it is located on it in the form of a cone. The angle between the generatrix of this cone and the horizontal plane is called the angle of repose of the granular-lumpy material.

The angle of repose is always greater than the angle of shedding (for the same material), since the presence of irregularities on the surface of the material prevents rolling, and even more so, sliding of pieces. The angle of repose largely depends on the fractional composition of the lump material, because the latter determines general structure cone surface. This heterogeneity in the size of the pieces causes at the same time the preferential rolling of large pieces of material onto the edge of the heap being poured, due to the fact that surface irregularities provide less resistance to rolling of large pieces.y pieces than small ones (Figure 2). The uneven distribution of pieces by size must be taken into account when loading packed absorbers, shaft furnaces, etc., since in the locations of large pieces, i.e. on the periphery, a larger cross-section of channels is obtained and the gas will flow predominantly through these channels, which have a smaller hydraulic resistance.

Finely ground materials have a larger angle of repose, i.e., less flowability, due to a more developed friction surface.

Figure 2

The angle of repose significantly depends on the moisture content of the material, because water, located on the surface of the pieces, causes them to stick together and thereby impedes the movement of individual pieces. The smaller the pieces of material, the greater the effect of humidity; but excessive moisture leads to an increase in the layer-by-layer fluidity of the liquid between pieces of material, and the angle of repose again decreases (Table 1).

Table 1

Breed

Angle of repose, degrees, for rock

dry

wet

wet

Coarse sand

30 – 35

32 – 40

25 – 27

Sand medium

28 – 30

Fine sand

30 – 35

15 – 20

Gravel

35 – 40

The angle of repose and the shedding angle decrease sharply with the movement of the material and the plane on which it lies. During shocks or vibrations, the material intensively crumbles, spreads, trying to take a horizontal position, since vibrations at certain moments reduce mutual friction along the surface of contact of the pieces with each other and the pieces with the plane. This is the basis for the use of vibration conveying devices, vibrators to facilitate the unloading of bins, dump trucks and dosing devices.

Knowledge of the angles of repose and fall is necessary when designing storage facilities, conveyors, shaft furnaces, where they deal with bulk materials. The impossibility of theoretically taking into account all the factors that determine the magnitude of these angles leads to the need for their experimental determination.


Description of installation. To determine the angle of repose, a smooth horizontal plane with divisions in centimeters marked on it and a short metal cylinder are used; to determine the pouring angle - a device consisting of a shaft 1 on which the cord is screwed, a bracket 2 through which the cord is connected to the lifting board 3, and an inclinometer 4 installed at the axis of rotation of the lifting board. The lifting board is equipped with a pointer that shows the angle of its rise on the protractor (Figure 3). A box was placed to collect the spilled mass. The work also uses a ruler, scales and a rectangular metal frame.


Figure 3

Conducting experiments and recording observations. When determining the angles of repose and dumping, bulk material of two or three sizes is used.

A. Determination of the angle of repose

1. Place the metal cylinder in the center of the horizontal plane,

2. Scoop up the bulk material and pour it into the cylinder.

3. Slowly lift the cylinder, allowing the material to scatter freely along the plane.

B. Determination of the pouring angle

1. Place a rectangular metal frame on the lifting board and completely fill it with bulk material.

2. Remove the rectangular frame and, slowly rotating the shaft, bring the lifting board into an inclined position.

3. When the material begins to crumble, stop lifting the board and record the angle of its inclination. Transfer all the material from the lifting board and its stand to a sheet of paper, weigh the material, add a certain amount of water (assigned by the teacher), mix thoroughly and make the same determinations with the wet material (steps A, 1 - 4 and B,

Enter the experimental results in Table 2.

table 2

Name of the material being studied

Angle of repose

Dumping angle

dry material

wet material

Dry material

Wet material

tan α

tan α

Processing the results of the experiment. Using the ratio, determine the value tan α and use the tables to find the corresponding value of α.

font-size:14.0pt; font-family:" times new roman>where α is the angle of repose, degrees;

H – height of the pile of material, cm;

D – diameter of the pile of material, cm;

font-size:14.0pt; font-family:" times new novel>– radius of the heap of material, cm,

1) Brief summary of the theory and purpose of the work.

2) Installation diagram.

3) Table 2.

4) Conclusion on the work.

Laboratory preparation assignment .

1) Grinding hard materials and their classification.

2) Grinding, screening and dosing solids.

Control questions .

1) Explain the concept of “rolling angle”.

2) Types of movement of lump material along the pouring plane.

3) Name the factors on which the angle of pouring of granular-lumpy material depends.

4) Explain the concept of “angle of repose of granular lump material”.

5) Name the factors on which the angle of repose depends.

6) Tell me which value is greater - the angle of shedding or the angle of repose, explain why.

7) How do the values ​​of the shedding angle and the angle of repose change with the movement of the material and the plane on which it lies?

8) How does the angle of repose depend on humidity?

9) does finely or coarsely ground material have a greater angle of repose?

10) Why is it necessary to know the angles of repose and fall?

When building foundations or laying communications in the ground, it is necessary to dig pits and trenches. Excavation work must be accompanied by safety measures. They determine the rules for securing the sides and bottom. To determine the slope angle of the pit, a table is used. Its use makes it possible to select the desired level of inclination of the walls of the dug recess to its bottom for the soil at the construction site, so that collapse does not occur.

Types of earthworks

The construction of buildings and communication structures involves labor-intensive excavation work. They mean the development of soil when digging pits and trenches, its transportation, and storage.

Earthen structures are embankments and excavations. They can be permanent or temporary. The first ones are made for long-term use. 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 noticeably in size. They are necessary for constructing foundations for buildings.

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

According to the requirements of GOST 23407-78, digging pits and trenches in populated areas, areas of traffic or people must be accompanied by the creation of protective fences. They are installed around the perimeter of the work area. Warning signs and inscriptions are placed on them, and even signal lighting is used at night. Bridges are also specially equipped for the movement of people.

Slopes are the inclined side walls of excavations or embankments. Important characteristic their is the slope (steepness). The horizontal surfaces surrounding the slopes are called berms.

The bottom of the recess is understood as its lower, flat part. The edge is the upper edge of the created slope, and the bottom is the lower part.


When operating earthen structures, they must not:

  • change its outlines and linear dimensions;
  • to sag;
  • eroded by water or susceptible to precipitation.

The laying of water pipelines, underground power lines, sewerage, and the construction of foundations for buildings cannot be done 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.

Types of pits

Digging holes for the foundation of a structure is a responsible task that requires a lot of time, money, and labor. Today, pits are usually divided according to the following criteria:

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

The walls of the pits can be:

  • vertical;
  • inclined;
  • stepped.

In order to carry out excavation work correctly, research is first carried out at 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 excavation depth;
  • establishing the presence of old communications;
  • determining the depth of groundwater;
  • analysis of local weather conditions.

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

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

If you plan to construct a shallow foundation of a strip or columnar type, then the soil can be developed without the involvement of machinery, manually. When it is necessary to build a house with a basement, or ground floor, then the work will need to use earth-moving mechanisms.

To extract the bulk of the soil from the excavation, various types of excavators equipped with a backhoe or a straight shovel are often used. Work related to digging a pit should be carried out without disturbing the density of the soil at the bottom of the foundation. This requirement is implemented in practice by its shortfall, the value of which ranges from 5 to 20 cm.

Workers clear the earth from the sides and bottom of the excavation to the planned level manually. In this case, you should definitely ensure that its walls are strengthened with the help of slopes, or through the installation of special structures. Precipitation and rise groundwater spring, summer, exposure to 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 soil water.

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

Types and purpose of trenches

Laying trenches for various communications is the most common type of excavation work. Digging them by hand is slow and expensive, so they often use equipment that they buy or rent.

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

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

There are 3 types of trench design:

  • rectangular;
  • trapezoidal;
  • mixed.

Inside trenches without sloped side walls, spacers are installed to increase the level of safety for people. Strengthening the slopes is not required, because they are made for the purpose of protection against landslides. Trenches intended for laying communications are dug at varying depths using different techniques.

Soil: groups and types

Due to the fact that earthworks are created in soils, you should definitely know their basic characteristics. It directly depends on them suitable type foundation. The choice is made taking into account achieving the highest possible level of reliability and durability of the foundation being built.

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

  • shape, size, strength, arrangement of particles included in its composition;
  • the degree of relationship between them;
  • the ability of constituent substances to solubilize and absorb moisture.

Soil is characterized using the following coefficients:

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

The classification involves dividing soils according to various criteria. There are the following types:

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

Depending on the water content, soil is distinguished:

  • 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.

CategoryIncluded soil varieties
1 sandy loam, sand, light loam (wet), peat, plant layer soil
2 light damp clay, fine to medium gravel, loam
3 dense loam, medium and heavy (loose) clay
4 frozen soils (clayey, loamy, peat, sandy, sandy loam, plant layer), heavy clay
5 fragile limestone and sandstone, strong clayey shale, permafrost (with admixtures of crushed stone, pebbles, boulders, gravel up to 10%), moraine and river (with large sizes boulders and pebbles up to 30%)
6 strong shales, clayey sandstone, marly limestone, fragile serpentine and dolomite, fluvial and moraine (inclusions of boulders and pebbles - up to 50%), permafrost (with a share of gravel, boulders, pebbles, crushed stone - up to 20%)
7 hard limestone and sandstone, dolomite, serpentine, mica and silicified schists, marble, permafrost (stone components account for up to 70% of the volume)

Soils are also divided into the following types:
  • quicksand;
  • soft;
  • average;
  • strong.

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

Excavation plan, requirements for them

Excavation work takes place in a number of stages. They are prescribed in SNiP 3.02.01-87. The main stages of the process are as follows:

  • carrying out preparatory activities;
  • experimental production part;
  • creating a pit or trench;
  • carrying out control activities;
  • acceptance of completed work.

SNiP 3.02.01-87 provides the following requirements:

  • developing a working draft is allowed only by specialists who have the necessary qualifications and experience;
  • communication and coordination of actions in matters of design, construction, and engineering solutions must be ensured between them;
  • It is constantly necessary to monitor the quality of construction work on site;
  • the project must be implemented by personnel with appropriate qualifications;
  • the erected structure may only be used for its intended purpose in accordance with the design;
  • activities for maintenance the structure and accompanying utilities must maintain it in a safe, working condition at all times during operation.

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

  • rules for organizing their construction;
  • standards for conducting geodetic work;
  • labor protection standards;
  • sections of the rules fire safety relating to construction work.

Earthen structures must be created strictly according to the current design.

Carrying out work with explosives requires compliance with appropriate safety rules during their production.

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

The following types of control during excavation work are distinguished:

  • input;
  • operating;
  • acceptance

Control is carried out in accordance with SP 48.13330.

Acceptance of work occurs with registration necessary documentation(acts) confirming their implementation.

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

Safety measures when digging pits

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

In order to prevent crumbling and reduce the possibility of material losses to a minimum, it is necessary to correctly calculate, at the design stage, in accordance with SNiP 111-4-80, the steepness of the slopes of the excavation being created.

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

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

  • prevent the possibility of collapses;
  • perform the optimal amount of excavation work;
  • will eliminate the cost of altering slopes during construction work.

Landslide prevention is a major safety concern for personnel.

Slope compliance optimal angles slope for this type of soil minimizes monetary and labor costs for backfilling and rework.

Before starting work, geological and hydrological surveys of the building site are carried out. In the presence of soil water, unstable soils, or if it is necessary to dig a 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, vertical side walls can be left when digging trenches or pits. In this case, there should be no structures near the excavations and no groundwater. The permissible depth of excavations for different soils with vertical walls is for:

  • gravel, sand – 1 m;
  • sandy loam – 1.25 m;
  • clayey and loamy - no more than 1.5 m;
  • very 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, flights of stairs are used.

The side surfaces of pits can be strengthened with construction. If there is a possibility of additional loads or slopes being washed out, they are covered with film or shotcrete is carried out (concreting with a thin layer).

Slope table

When you need to dig a hole at least 1.5 m deep, then you should take the slope angle of the pit 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 construction literature, standards, and rules, the steepness of an excavation slope is measured in degrees (angle), or as the ratio of its height to the foundation.

A table of slope steepness 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 soil mass under the influence of the weight of the equipment involved. Therefore, the distance from the parking lot of cars to their sole is also regulated by SNiP.

When there is soil on the construction site different types, 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 using an excavator to prevent the possibility of landslides and collapses.

The walls of excavations up to 3 m deep are secured according to design instructions.

If the cohesion of the soil 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 lesser steepness, or with indents.

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

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

Pit pits or trenches dug in autumn or winter frosts, during spring thaws, they must inspect and determine the stability of their slopes.

With the slope angles discussed in the table for each type of soil and pit depth, workers can be in the excavation without the need to secure the slopes. If the slopes have been moistened, then before starting work they are inspected for cracks and peeling.

Methods of excavation work, mechanisms used

Depending on the soil, when constructing trenches and foundation pits, it is used different equipment, apply various methods conducting development of construction sites. They differ in labor intensity and level of required material costs. According to SNiP 111-4-80, the following methods are identified:

  • hydromechanical;
  • mechanical;
  • carrying out blasting operations.

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

The hydromechanical method is based on eroding the soil mass with a jet of water from a hydraulic monitor. Then the resulting solution is sucked into the dredge.

Blasting works are used mainly when carrying out suburban construction. First, holes (wells) are drilled in the ground. Then they put explosives in them and detonate them. The resulting loose mass is removed using machinery.


The mechanical method consists of a number of stages:

  • loosening the soil;
  • development of rock mass;
  • its transportation;
  • leveling, compacting side slopes and bottom.

Work on creating recesses using a hydromechanical method takes place in the following sequence:

  • designate the work site area using fences, inscriptions, and warning signs;
  • according to the standards, a hydraulic monitor is installed, manually controlled by the operator: the distance from its nozzle to the wall of the pit must be no less than the height of the excavation, and to the nearest overhead power line - at least two intervals over which a stream of water can be supplied by this equipment;
  • Slurry pipelines and water conduits are placed behind the security perimeter of power lines;
  • protect the dumping areas of the reclaimed earth mass;
  • produce erosion and excavation.

It is prohibited to operate the hydraulic monitor during a thunderstorm.

Conducting blasting operations is regulated by relevant rules.

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

Any equipment must be located during operation in accordance with current standards and rules. Deviation from them often causes accidents.

Soil stabilization technologies

Depending on the geological characteristics of the construction site and climatic features terrain, excavation depth, features of the building being constructed or reconstructed are used in practice various ways consolidation of soils. Technologies can improve their resistance to destruction. SNiP111-4-80 highlights following methods fastenings:

  • thermal;
  • cement;
  • using cement mortar.

Very often used different kinds mechanical fastenings. Based on their design, the following types are distinguished:

  • braced;
  • cantilever-spacer;
  • spacer;
  • cantilever-anchor;
  • console

The choice of fastening type is made based on the above factors affecting correct execution works

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

  • stationary;
  • inventory;
  • with 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 carried out from top to bottom during the excavation of earth masses, and disassembly is carried out in the opposite direction when backfilling.

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

  • shields;
  • screw spacers or frames;
  • racks

The side surfaces of the trenches are secured immediately after their excavation.

On weak, wet soils, cantilever-spacer or cantilever types of fastenings are used. The depth of the excavations should be within 3 m.

A type of cantilever-type fastenings are tongue-and-groove fastenings. They secure the walls of deep pits, where there is great pressure from the sides and difficult hydrogeological conditions.

Strut fences are rarely used because they make work difficult.

The method of fastening is determined project documentation. If these measures are necessary during individual development, you can rent various fasteners, or make metal or wooden analogues of factory-made products yourself. Determining the choice in favor of one or another fastening option depends on the conditions at the construction site.

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


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


Giving stability to the side surfaces of pits is the first requirement that is presented when creating them. In order to ensure safe conditions labor, prevention of landslides and compliance with construction technology, excavations with slopes of the required steepness are 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, but for hard rocks it is left vertical walls excavations and when deepening up to 2 m. The slopes of pits are formed according to SNiP tables if the depth is up to 5 m. After exceeding this value, special calculations are performed.


The angle of natural repose of the soil is the greatest value of the angle that the surface of the soil, filled without shocks, forms with the horizontal plane; shaking and vibrations.
The angle of repose depends on the shear resistance of the soil. To establish this relationship, let us imagine a soil body dissected by a plane a - a, inclined to the horizon at an angle a (Fig. 22).

The part of the soil above the plane a - a, considered as a single mass, can remain at rest or move under the influence of the force P - its own weight and the influence of the structure erected on it.
Let us decompose P into two forces: N = P cos a, directed normal to the a - a plane and the force T = P sin a, parallel to the a - a plane. The force T tends to move the cut off part, which is held by the forces of adhesion and friction in the a - a plane.
In a state of limit equilibrium, when the shear force is balanced by the resistance of friction and adhesion, but when there is no shear yet, equality 26 is satisfied, i.e. T = N tg f + CF.
IN clay soils shear is primarily resisted by adhesion.


In dry sand there is almost no cohesion and the state of limiting equilibrium is characterized by the relation T = N tg f. Substituting the values ​​of N and T, we obtain P sin a = P cos a tan f or tg a = tan f and a = f, i.e. angle a corresponds to the angle of internal friction of the soil f in the state of limit equilibrium of a mass of non-cohesive soil.
Determination of the angle of repose of sand is shown in Fig. 23. The angle of repose of sand is determined twice - for the condition natural humidity and underwater. To do this, sandy soil is poured into a glass rectangular vessel, as shown in Fig. 23, a. Then the vessel is tilted at an angle of at least 45° and carefully returned to its previous position (Fig. 23, b). Next, the angle a between the resulting sandy soil slope and the horizontal is determined; the magnitude of the angle a can be judged by the ratio hl equal to tan a.

IN last years To determine the shear resistance characteristics of soils, a number of new methods have been proposed: according to soil testing in stabilometers (see Fig. 11), by pressing a ball stamp into the soil (Fig. 24), similar to the determination of hardness according to Brinell et al.
Testing soil using the ball test method (Fig. 24) consists of measuring the settlement of a ball S under the action of a constant load p.
The value of equivalent soil adhesion is determined by the following formula:


where P is the full load on
D - ball diameter, cm;
S - ball draft, cm.

The magnitude of adhesion ssh takes into account not only the adhesion forces of the soil, but also internal friction.
To determine the specific adhesion c, the value of csh is multiplied by the coefficient K, which depends on the angle of internal friction f (deg).

In recent years, the ball test method has begun to be used in field conditions. In this case, hemispherical stamps up to 1 m in size are used (Fig. 25).
The shear characteristics f and c are called strength characteristics and the accuracy of their determination is great importance when calculating the foundations of structures for strength and stability.