Expansive soil direct shear test device and shear strength measurement method

Abstract

The invention provides an expansive soil direct shear test device and a shear strength measurement method. The device comprises a strain type direct shear instrument and a loading plate, wherein the loading plate is provided with a limiting structure and a pressure sensor; a larger overlying load is applied before a sample is soaked in water, the limiting structure controls the bottom surface of the loading plate to be contacted with the top surface of porous stone at the upper part of the sample, and the sample is not affected by the overlying load. The measurement method comprises steps as follows: static-pressure sample preparation is carried out according to geotechnical test rules of roads, the sample is soaked in water in constant volume, vertical expansive force is measured, a direct shear test is performed with the vertical expansive force as the overlying load, and effective cohesion and effective internal friction angle of experimental expansive soil are obtained. The test device and the method have the advantages of being simple, convenient to operate, reasonable in structure and economical and guarantee consistent micro-structure before sample shear under the action ofdifferent overlying loads in the direct shear test, so that the problem that shear strength parameters of expansive soil cannot be accurately obtained for a long time in the field is solved, and accurate design parameters are provided for civil engineering structure design of the expansive soil.

Description

Technical field [0001] The invention discloses a direct shear test device and a method for measuring the shear strength of expansive soil; it belongs to the technical field of geotechnical test measurement. Background technique [0002] Expansive soil spreads to more than 40 countries on six continents in the world. China is one of the countries with the most extensive distribution of expansive soil. This special soil exists in 26 provinces, autonomous regions, and municipalities directly under the Central Government. Compared with ordinary clay, expansive soil is rich in montmorillonite And its mixed layer minerals, when the moisture content increases and accepts a small constraint, it will produce expansion deformation and a sharp decline in strength; and when its swelling is subject to certain constraints, it will produce non-negligible expansion of the surrounding soil and structures Additional stress. Therefore, expansive soil excavation and filling slopes in highways, rail...

AI Technical Summary

Problems solved by technology

The prior art adopts the above-mentioned loading device, structure and method, which has the following defects: due to the use of loading plates and permeable stones with the same size and area to apply different overlying loads to the sample before immersion, at this time, the sample is overlying Under load, a certain degree of compression will occur, and its dry density will change relative to the initial dry density set during sample preparation

Therefore, expansion deformation may have an impact on the effective stress shear strength index of expansive soil

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