A method for measuring the embedding amount of sample rubber film in large-scale triaxial test of coarse-grained soil

Abstract

A method for measuring the penetration quantity of a rubber membrane in large-scale triaxial test of coarse-grained soil belongs to the technical field of geotechnical tests. The measurement method ischaracterized in that a small confining pressure cyclic loading process is arranged in a conventional isotonic consolidation test, the volume variation quantity of a recoverable sample under a smallconfining pressure increment condition under different confining pressures is measured, and the measurement of the penetration quantity of the rubber membrane and the change law of the penetration quality with the confining pressure is realized based on the penetration recoverability of the rubber membrane. The measuring method is easy to implement in a conventional triaxial apparatus, has the advantages of simple operating steps and low difficulty, can be coupled to a conventional consolidation test process without affecting subsequent test, avoids the links of a development device, multi-time sample production and multi-group test in some measuring methods, effectively eliminates the influences of the individual discreteness of the sample, can accurately measure the penetration quantityof the rubber membrane changing with the confining pressure, provides a reliable technical way for correcting the volume deformation of the coarse-grained soil sample in the triaxial test, promotes the study of the mechanical properties and the constitutive model of he coarse-grained soil, and has good promotion values.

Description

technical field [0001] The invention relates to a method for measuring the embedding amount of a sample rubber film in a large-scale triaxial test of coarse-grained soil, and belongs to the technical field of geotechnical tests. Background technique [0002] In a triaxial test, the confining pressure is transmitted to the specimen through a rubber membrane. However, due to the unevenness of the sample surface, the rubber film will be embedded in the pores between the particles on the sample surface after the confining pressure is applied, and the embedded depth will change with the effective confining pressure. This phenomenon is called rubber film embedding. In the conventional triaxial drainage shear test, the method to determine the volume change of the saturated sample is to measure the amount of water discharged or absorbed by the sample, but due to the influence of the rubber film embedding, the volume change measurement includes the embedding error of the rubber film,...

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Problems solved by technology

This method needs to be based on two triaxial instruments of different sizes. For larger coarse-grained soils, this method needs to develop a super-large triaxial instrument, so it is difficult to apply to the measurement of rubber membrane embedding in coarse-grained soils.

[0006] Special device method: This method is to obtain the relationship between the amount of rubber film embedded and the area of ​​the rubber film by making a special device, but the stress state and boundary conditions of the rubber film embedded by this method are different from those of the triaxial test and cannot fully reflect The embedding amount of the rubber film during the routine triaxial test

[0007] Local strain measurement method: For the case of large sample size, the space in the pressure chamber is sufficient, the axial and radial displacement sensors can be used to measure the volume change of the sample skeleton, and then the embedding amount of the rubber film can be calculated according to the volume change of the drainage, but under the confining pressure Under changing conditions, the embedding of the rubber film, the inhomogeneity of the radial deformation of the cylindrical sample, and the deformation of the rubber film along the thickness direction will all affect the measurement accuracy of the radial deformation of the cylindrical sample

[0008] Isotropic assumption method: This method assumes that the deformation is isotropic during the initial equal pressure test to obtain the actual deformation of the soil skeleton, but this assumption is quite different from the actual one, especially the skeleton of the sample during the initial equal pressure loading process. The larger the drainage body (including plastic and elastic deformation, mainly the former), the error caused by this assumption will be amplified

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