Values ​​for angles of repose for sands. Earthworks in construction

General provisions

angle of repose a is called the angle at which an unreinforced slope of sandy soil maintains balance, or the angle at which freely poured sand and other bulk materials are located.

Angle of repose a is determined in an air-dry state and under water using a disk having a vertical calibration rod

1. To determine the angle of repose in an air-dry state, the disc is placed in a glass jar, a casing is placed on the disc.

2. Sand is poured into the casing in a naturally dry state.

3. The casing is smoothly removed from the disk, and the excess sand falls off, and a cone of sand remains on the disk, the top of which, at the point of contact with the rod, shows the value of the slope angle.

4. To determine the angle of repose under water, the disc is placed in a glass jar, and a casing is placed on the disc.

5. Sand is poured into the casing in a naturally dry state.

6. The jar is filled with water to the top of the casing.

7. Sand that has settled in the casing is filled up to the top.

Angle of repose or rest angle - 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 is the maximum slope angle of granular non-cohesive material, i.e. free-flowing material. Loose and porous bulk cargoes have a greater angle of rest than solid lump cargoes. With increasing humidity, the angle of rest increases. During long-term storage of many bulk cargoes, 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 in motion (for example, on a conveyor belt).

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

particles, humidity of the mass of the cargo, method of its dumping, initial state and material of the supporting surface.

Various methods are used to determine the magnitude of the angle of repose; the most common methods are filling and caving.

Experimental determination of the shear resistance and the main parameters of the load is usually carried out by direct shear, uniaxial and triaxial compression methods. Tests of cargo properties by direct shear methods are 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 granular bodies under the conditional assumption that a uniform stress state is maintained at all points of the test sample. The most reliable results of testing the characteristics of a coherent granular body are obtained by the triaxial compression method, which makes it possible to investigate the strength of a load sample under all-round compression.

Determination of the angle of repose of fine-grained substances (particle sizes less than 10 mm) is carried out using a "tilted 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 mass shedding of the substance in the box begins.

The ship 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 repose or rest angle - e then the angle between the plane of the base of the stack and the generatrix, which depends on the type and condition of the cargo. The angle of repose is the maximum slope angle of non-cohesive granular material, i.e. free-flowing material.

In practice, data on angle of repose are used in determining the area of ​​cargo stacking, the amount of cargo in the stack, the volume of intra-hold stowage work, when calculating the pressure of the cargo on its enclosing walls

Various methods are used to determine the magnitude of the angle of repose; The most common methods are embankments and collapse.

Experimental definition shear resistance and the main parameters of the cargo is usually produced by methods straight cut, uniaxial and triaxial compression.

Determining the angle of repose fine-grained substances(particle sizes less than 10 mm) is produced using " 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 mass shedding of the substance in the box begins.

ship method determination of the angle of repose of a 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 changes depending on the dumping method cargo (jet or rain), masses investigated cargo, heights, with which experimental filling is performed.

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

Objective:

Familiarization with the method of determining the angle of repose for sandy soils.

Acquisition of skills in working with a device for determining the angle of repose of loose soils.

Determination of the angle of repose of sand in air-dry and underwater conditions.

Necessary equipment and materials

Methodological instructions for the performance of work.

Journal of laboratory work.

An instrument for determining the angle of repose of Litvinov's field laboratory.

Water container.

The lack of cohesion in the sands makes it possible to determine the angle of internal friction φ 0 from the angle of repose of the soil under conditions of limit equilibrium (Fig. 2.3.).

Fig.2.3. Scheme for determining the angle of repose of a sand grant.

T1 =

where φ is the angle of internal friction; tg φ – coefficient of friction

The angle of repose of sandy soil is the maximum value of the angle formed with the horizontal plane, the surface of the soil, filled without shocks and dynamic influences.

The angle of repose is determined for sandy soil in the air-dry state and under water. For testing, we use the Litvinov device.

Work order

The determination of the angle of repose of the soil in the air-dry state is carried out as follows. The device is installed on the table, while the sliding sash is lowered to the bottom. The test sand is poured into the small compartment of the device to the top (Fig. 2.4). After that, the sliding sash is gradually raised without pushing; while the device is held by hand. The soil is gradually partially poured into another compartment until an equilibrium position is reached.

Rice. 2.4. General view of the instrument for determining the angle of repose of sands (Coulomb box).

The angle between the free slope plane and the horizontal plane is the angle of repose. According to the divisions on the bottom and side wall, the height and laying of the slope are counted and the tangent of the angle of repose is calculated; readings are carried out with an accuracy of 1 mm.

Determination of the angle of repose of the soil in the underwater state differs from the previous one in that after the test soil is poured into the small compartment of the device, water is poured into the large compartment to the top. The upper sash is raised a few millimeters so that water can penetrate into the small compartment. When all the soil is saturated with water, raise the sash higher and continue the test in the same way as the previous one. The test results are entered in table 2.4.

Angle of repose

Angle of repose

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

According to the angles of repose, the maximum allowable angles of slopes of ledges and sides of quarries, embankments, dumps and piles are determined. angle of repose of various materials

List of various materials and their angle of repose. The data is approximate.

see also

Notes

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See what the "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 ​​(VNIIIS Gosstroy of the USSR)] angle ... ... Technical Translator's Handbook

The maximum angle of inclination of the slope, folded by the gp, at which they are in balance, i.e., they do not crumble, do not creep. Depends on the composition and condition of the settlements that make up the slope, their water content, and for clayey settlements, the height of the slope. Geological … Geological Encyclopedia

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

angle of repose- The ultimate 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 the slope with a horizontal surface during the dumping of 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 REVERSE- the angle at which the unreinforced slope of sandy soil still maintains balance, or the angle at which freely poured 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 during the free pouring of 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 a free slope of loose soil with a horizontal plane, at which there is no violation of the stable state (Bulgarian; Bulgarian) ъгъл on a natural slope (Czech; Čeština) úhel přirozeného… … Construction dictionary

Ecological dictionary

SOIL SLOPE- (soil) the largest possible angle that a stable slope of an embankment of dry soil (soil), or wet soil (soil) under water, forms with a horizontal surface. Ecological Dictionary, 2001 The angle of repose of the soil (soil) ... ... Ecological dictionary

Angle of repose- this is the largest angle that can be formed by a slope of freely poured soil in equilibrium with a horizontal plane.

The angle of repose depends on particle size distribution and particle shape. As the grain size decreases, the angle of repose becomes flatter.
In the air-dry state, the angle of repose of sandy soil is 30-40°, under water - 24-33°. For non-cohesive (loose) soils, the angle of repose does not exceed the angle of internal friction

To determine the angle of repose of sandy soil in an air-dry state, the UVT device is used ( rice. 9.11, 9.12), under water - VIA ( rice. 9.13).

According to rice. 9.12 when the box is tilted, the sand crumbles and, loosening, forms a slope with an angle that can be determined by a protractor or by the formula

The concept of angle of repose applies only to dry loose soils, and for cohesive clay soils it loses all meaning, since in the latter it depends on moisture content, slope height and slope load and can vary from 0 to 90 °.

Rice. 9.11. UVT-2 device: 1 - scale; 2 - tank; 3 - measuring table; 4 - clip; 5 - support; 6 - sand sample

Rice. 9.12. Determining the angle of repose by rotating the container (a) and slowly removing the plate (b): A - axis of rotation of the container

Rice. 9.13. VIA device: 1 - VIA box; 2 - sand sample; 3 - container with water; 4 - protractor; 5 - axis of rotation; 6- piezometer; 7- tripod

During the development and shrinkage of the loosened soil cuts and embankments form natural slopes of various steepness. The greatest steepness of flat slopes of earthworks, trenches and pits, arranged without fasteners, should be taken according to tab. 9.2. When ensuring the natural steepness of the slopes, the stability of earthen embankments and excavations is ensured.

Table 9.2. The greatest steepness of slopes of trenches and pits, hail.

The slopes of embankments of permanent structures are performed more gentle than the slopes of excavations.