RU2569915C1 - Determination of soil density at compression tests - Google Patents

Abstract

FIELD: mining.

SUBSTANCE: claimed process comprises the determination of the soil specimen main bulk. Measurements are executed at, at least, two pressure stages (in odometer). Note here that at pressure increases from the step to another one, the soil deformation increment is measured up to deformation stabilization. Note here that, additionally, the extra specimen of made. Then, extra identical specimen is dried to a constant mass. Then, it is dried to said constant mass. Now, dried soil specimen weight and volume are measured to calculate the dried soil initial density. Then, the specimen density is defined for all pressure stages. Note also that drying can be made up to 105°C to settling of the constant mass. Soil density for all pressures can be defined by he formula

, where ρ_d,₀ is dry soil density, h₀ is the specimen initial height, Δh is the absolute specimen deformation.

EFFECT: expanded applications.

2 cl

Description

The invention relates to the field of engineering geology, in particular to the determination of the physical characteristics of soils, and can be used when testing soil samples under conditions of the impossibility of lateral expansion (compression tests).

The well-known "METHOD OF LABORATORY DETERMINATION OF THE MAXIMUM DENSITY OF SOIL AND DEVICE FOR ITS IMPLEMENTATION" RU 2328718 [1], which consists in the fact that to determine the characteristics of the soil by impacts of it alternately lifted and dumped tared cargo from a given height collect the container, set it hard, set it fixed base, load into it a layer of a moistened soil sample prepared for testing and install an anvil on it, and then install a rod with a movable anvil This layer of soil sample is compacted with an arided load and by alternately lifting the load to a predetermined height and dropping the load onto the anvil with a specified number of strokes, and after processing the data on the required number of samples, the dependence of the density of the soil skeleton on moisture is established and the maximum density of the soil skeleton is determined from the schedule of this dependence ( Y max) and optimum humidity (W opt) at which the maximum density is reached.

The disadvantages of the known design is the inaccuracy in determining the characteristics of the soil, determined by the pulsed nature of the impact on the soil.

Closest to the claimed technical solution is the "METHOD FOR STABILIZING A SAND SOIL BASIS" RU 2098553 [2], including determining the volume of a soil sample, measurements are made at more than two pressure steps (in the odometer), and with increasing pressure from the step to the step, the strain increment is measured soil (during measurement, the samples are maintained until the deformation is stabilized).

The known method allows to obtain more accurate and objective measurements of the compression parameters of the soil in comparison with [1].

The disadvantage of this method is the inability to determine the relationship of the deformation characteristics of soils from indicators of their physical properties and, accordingly, the narrow scope of the method.

The technical result of the invention is the expansion of the scope due to the possibility of determining the density of dry soil at all pressure levels without additional operations and measurements.

The technical result is achieved by the fact that the method of determining the density of dry soil during compression tests, including determining the volume of the main soil sample, measurements are performed at more than two pressure levels (in the odometer), and when the pressure increases from step to step, the soil strain increment is measured (when measuring the samples are maintained until the deformation is stabilized), characterized in that they additionally produce an additional identical sample identical to the main one, and additional dentichnogo soil sample until a constant weight was measured weight and volume of the dried soil sample, calculate the initial density of the dried soil is then determined by calculating the density of the soil at all pressure levels.

Drying of soil samples can be done at 105ºC until a constant weight is established. The indicated drying parameters make it possible to reliably remove water with little destruction of the initial structure of the sample.

, где

- начальная плотность сухого грунта; h₀ - начальная высота образца грунта; Δh=h_i-h₀ - абсолютная деформация.The soil density for all pressure values can be determined by the formula

where

- initial density of dry soil; h ₀ is the initial height of the soil sample; Δh = h _i -h ₀ is the absolute deformation.

This formula allows you to determine the density at all pressure levels with a minimum set of calculated parameters.

The characteristics of the deformation properties of soils are determined by the results of tests of samples in compression devices (odometers), which exclude the possibility of lateral expansion under the action of vertical pressure. Usually, instruments are used with loading the samples in stages with holding at each pressure stage until the deformations are conditionally stabilized. During the experiments, deformations of the sample are recorded at each pressure stage.

To determine the compressibility coefficient a ₀ and the deformation modulus E from the test results at each stage, calculate:

- absolute vertical deformation of the soil sample Δh;

- relative vertical deformation of the soil sample

- coefficient of porosity of the soil e _i at a pressure p _i according to the formula

where e _o is the initial coefficient of porosity; p _i is the pressure on the sample;

The initial values of the physical characteristics of the soil are determined by calculation from the measured values of the mass m and the volume V of the sample, the mass of the dry sample m _d and the volume of solid particles V _d :

- density of dry soil

- soil moisture

- porosity coefficient

- relative air content [1]

From the indicators of soil physical characteristics given in (1 - 5) at each pressure stage of compression tests, only the porosity coefficient is determined by the formula (1). During the compression testing of the samples, the dry soil mass m _d remains constant.

The method for determining the density of dry soil ρ _d during compression tests is that two identical samples are made from the test soil. One sample is used to determine the physical characteristics of the soil, including the initial density of dry soil ρ _{d, 0} . To do this, determine the initial volume of the sample V ₀ , dry it at a temperature of 105 ^º C to establish a constant mass, determine the mass of the dried sample m _d and calculate the initial density of dry soil by the formula

The second sample is placed in the metal cylinder of the compression device, it is tested under stepwise increasing pressure with exposure at each stage until the deformation is conditionally stabilized and the absolute deformation of the sample Δh is determined. When tested in conditions of the impossibility of lateral expansion, the volume of the sample changes only due to a change in its height and is determined by the formula

where S is the cross-sectional area of the sample, h ₀ is the initial height of the sample.

Since the mass of dry soil m _d = ρ _{d, 0} Sh ₀ remains unchanged, its density at all pressure levels based on dependencies (6) and (7) is determined by the formula

Porosity and porosity coefficient are determined respectively by the formulas

Substituting the found expression (8) into (9) and (10), we find the porosity and porosity coefficient at all pressure steps

Thus, at all pressure levels during compression tests of thawed soils, it is possible to establish the dependences of the compressibility coefficient a, porosity n, and porosity coefficient e on the density of dry soil ρ _d .

The technical result - the expansion of the scope is achieved by using a comparative analysis of soil samples, including melt to obtain the whole set of deformation characteristics of the soil.

Industrial application. The proposed method for measuring the deformation characteristics of soils during compression tests can be successfully used for soil research.

Claims (2)

1. The method of determining the density of dry soil during compression tests, including determining the volume of the main soil sample, the measurements are made at more than two pressure levels, and when the pressure increases from step to step, the soil strain increment is measured, characterized in that an additional additional sample identical to the main one is additionally made dry an additional identical soil sample to dry until a constant mass is established; measure the mass and volume of the dried soil sample; vayut initial density of the dried soil is then determined by calculating the density of the soil at all pressure levels. 2. The method according to claim 1, characterized in that determine the density of the soil for all pressure values according to the formula

,
Where $${\rho }_{d,o}$$

- density of dry soil,
h $${}_o$$

 - the initial height of the sample,
$$\Delta h$$

 - absolute deformation of the sample.