UA11675U - Method for determining deformation parameters of porous material by the data of laboratory tests - Google Patents

Abstract

The proposed method for determining deformation parameters of porous material by the data of laboratory tests accomplished in two stages consists in axially compressing the material sample, without a possibility for the lateral expansion of the sample, and measuring the axial force and the axial deformation of the sample, at the first stage of the tests, and loading the sample by a radial force, without a possibility for the elongation of the sample, and measuring the pressure in the radial direction and the expansion of the sample. The test results are used to determine the coefficient of elasticity and the Poisson's ratio of the material.

Description

Description of the invention

A useful model refers to the field of laboratory testing of porous materials and can be used to determine their deformation parameters.

A well-known (1, p. 16) method of laboratory compression tests of soils (prototype), which consists in the fact that a soil sample is placed in a holder with rigid walls and through a stamp installed on its surface, an axial force varying in degrees or nonstop. In the process of loading, the displacement of the stamp caused by the deformation of the sample is measured, which takes place without the possibility of lateral 70 expansion. Based on the results of the tests, the soil deformation module is determined, which is used in the calculation methods accepted by the design standards, which are based on the model of linear deformation medium.

According to the concept of the theory of linear deformation medium, this medium should be characterized by two deformation parameters, for example, the deformation modulus E and the Poisson ratio y. 15 The disadvantage of the described compression tests in relation to the task of determining the deformation characteristics of the soil or porous material is the impossibility of determining the specified two parameters based on the results of such tests; in principle, it is possible to determine only the ratio of these parameters.

Usually, the Poisson's ratio y is considered known, and the value of the deformation modulus E is determined by linearizing the compression curve. This naturally reduces the reliability of the test results. 20 The basis of a useful model is the task of increasing the reliability of test results.

The task is solved by the fact that in the proposed method of determining the deformation parameters of porous materials based on the results of laboratory tests, which consists in the fact that a sample of porous material in the form of a hollow cylinder is placed in a holder with rigid walls and loaded with external pressure with simultaneous measurement of displacements, tests of porous material 25 is carried out in two stages: - - in the first stage, axial compression of the sample in the holder is carried out without the possibility of lateral expansion, vertical stresses c and deformations dp are measured, which change during the loading process, and the equation of the relationship between the deformation modulus E and the Poisson ratio y is obtained ; у зо - at the second stage, in the same holder, radial loading of the hollow cylindrical sample is carried out without the possibility of axial deformations, the radial pressure and displacement of the internal cylindrical surface of the sample, which change during the loading process, are measured, and the second equation of the relationship between the parameters Е and со is obtained y Two deformation parameters of the porous material are uniquely determined from the two obtained expressions.

Figures 1, 2 illustrate the proposed useful model. - 35 Fig. 1 shows the diagram of the first stage of the test. "-

Figure 2 shows the diagram of the second stage of the test.

Testing of porous material is carried out in two stages. At the first stage (Fig. 1), axial compression of the sample is carried out in the holder without the possibility of lateral expansion and the vertical stresses c and deformations dp are measured, which change during the loading process, and at the second stage (Fig. 2) in the same holder, a "40 radial load on the inner surface of the hollow cylindrical sample without the possibility of axial c deformations and measure the radial pressure P and displacement 5 of the inner cylindrical surface of the sample, which change during the loading process. "" Conducting tests in two stages allows, based on their results, to unambiguously determine two deformation parameters of the porous material, Е and у. 45 According to the results of the tests, at the first stage, a curve is constructed, stress s - deformation г, - linearizing it in the area of the bend and using the formulas of Hooke's generalized law, obtain the relationship between - the modulus of deformation E and Poisson's ratio in

Ф 2 - 20 v- 10 de 1- m sl where E - modulus of deformation;

As - stress increase; two 7 - increase in vertical deformations; y is Poisson's ratio. c At the second stage, the dependence between the pressure P on the inner surface of the cylinder and the radial displacement of 5 points lying on this surface is obtained from the experiment. The well-known Lamé solution for thick-walled cylinders makes it possible to obtain the second relationship between the deformation parameters EE and 60

E-koa, o and where E is the modulus of deformation; 65 AR - pressure increase in the sample cavity; - increase in radial movements of the inner surface of the cylindrical sample;

Ku is a coefficient that depends on the size of the sample and Poisson's ratio.

From the two equations (1) and (2), the two parameters Е and у of the porous material are uniquely determined.

Thus, the proposed method of laboratory tests of porous materials avoids the noted drawback of standard compression tests - the arbitrary assignment of the value of the coefficient

Poisson when determining the modulus of deformation of a porous material based on test results.

Sources of information: 1. The industrial, residential, and public designer's directory was submitted and compiled. Foundations and foundation. Under ed. WE. Gorbunova-Posadova. L.:, M.: Stroyizdat, 1964, -268b.

Claims (1)

The formula of the invention is the method of determining the deformation parameters of porous materials based on the results of 75 laboratory tests, which consists in the fact that a sample of porous material in the form of a hollow cylinder is placed in a holder with rigid walls, loaded with external pressure with simultaneous measurement of movements, which differs in that the test of porous material carried out in two stages: in the first stage, axial compression of the sample in the holder without the possibility of lateral expansion is carried out, vertical stresses a and deformations Ap are measured, which change during the loading process, and the equation of the relationship between the deformation modulus E and Poisson's ratio is obtained ri 1- - zm LE 1-x where E is the modulus of deformation; Ac - increase in stress; Ah - increase in vertical deformations; в-в у - Poisson's ratio, at the second stage, in the same bracket, radial loading of a hollow cylindrical sample is carried out without the possibility of axial deformations, measured radial pressure and displacement of the internal cylindrical po the top of the sample, which change during the loading process, and obtain the second equation of the relationship between the parameters of the modulus of deformation E and the Poisson's ratio "ych-AR; E-KOM--- XE (Se) where E is the deformation modulus; h- AR - pressure increase in the sample cavity; Zoya increase in radial movements of the inner surface of the cylindrical sample; Ko") - a coefficient that depends on the size of the sample and Poisson's ratio, from the two obtained expressions, two deformation parameters of the porous material are uniquely determined. " - and? - - (o) - and sl 60 b5