Expansive soil direct shear test device and shear strength measurement method

Abstract

A direct shear test device for expansive soil and a method for measuring shear strength. The device includes a strain type direct shear instrument and a loading plate. The loading plate is provided with a limit structure and a pressure sensor. Load, the limit structure controls the bottom surface of the loading plate to just contact the top surface of the permeable stone on the upper part of the sample, and ensures that the sample is not affected by the overlying load. The measurement method: press the sample statically according to the road geotechnical test regulations, soak the sample in water at a constant volume, measure the vertical expansion force, and use the vertical expansion force as the overlying load to perform a direct shear test to obtain the effective cohesion and effective internal friction angle. The test method and device of the invention are simple, easy to operate, reasonable in structure, and economical in cost, and ensure that the microstructure of the sample before shearing is consistent under different overlying loads in the direct shear test, which solves the problem that the field has not been able to accurately obtain the resistance of expansive soil for a long time. The problem of shear strength parameters provides accurate design parameters for the design of expansive soil civil engineering structures.

Description

technical field [0001] The invention discloses an expansive soil direct shear test device and a shear strength measurement method, belonging to the technical field of geotechnical test measurement. Background technique [0002] Expansive soils are distributed in more than 40 countries on six continents in the world. my country is one of the countries with the widest distribution of expansive soils. This special soil exists in 26 provinces, autonomous regions, and municipalities directly under the central government. Compared with ordinary clay, expansive soils are rich in montmorillonite. And its mixed layer minerals, when the water content increases and is subject to a small constraint, it will cause expansion deformation and sharp attenuation of strength; and when its wet expansion is subject to certain constraints, it will cause non-negligible expansion to the surrounding soil and structures additional stress. Therefore, the expansive soil excavation and filling slopes in ...

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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