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Expansive soil direct shear test device and shear strength measurement method

A technology of shear strength and measurement method, applied in the direction of applying stable shear force to test material strength, measurement device, strength characteristics, etc., can solve the impact of expansive soil effective stress shear strength index, dry density dry density change, etc. question

Active Publication Date: 2021-05-14
CHANGSHA UNIVERSITY OF SCIENCE AND TECHNOLOGY
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

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

Method used

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  • Expansive soil direct shear test device and shear strength measurement method
  • Expansive soil direct shear test device and shear strength measurement method
  • Expansive soil direct shear test device and shear strength measurement method

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Effect test

Embodiment 1

[0068] See attached figure 1 a, an expansive soil direct shear test device of the present invention, comprising a strain type direct shear instrument and a loading plate 4, the loading plate 4 is provided with a limit structure, when the sample is placed in the shear box 1 of the strain type direct shear instrument Before soaking in water, when the loading plate 4 is installed on the shear box 1 of the strain type direct shear instrument, the limit structure controls the bottom surface of the loading plate 4 and the sample 3 to realize no gap contact but does not apply a load to the sample;

[0069] Described loading plate 4 is made up of lower cylinder and loam cake, and the diameter of described loam cake is greater than the diameter of lower cylinder, forms a positioning boss between the column body of lower cylinder and the bottom surface of loam cake, makes the lateral of loading plate The cross-section is a "T"-shaped structure; the diameter of the lower cylinder of the...

Embodiment 2

[0072] The undisturbed soil samples and disturbed soil samples of expansive soil were collected on the Baise Expressway in Guangxi, and the basic physical property indexes and engineering property tests were carried out. The indoor test results show that the plasticity index of the expansive soil sample of Baise Expressway is 33.5%, and the free expansion rate is 63%. According to the current expansive soil identification and classification standards for highways, the soil samples taken are medium expansive soils. Adopt a kind of expansive soil direct shear test device and shear strength test method of the present invention, sample preparation is carried out to Guangxi expansive soil and carry out direct shear test, concrete implementation steps are as follows:

[0073] According to the initial dry density of 1.40g / cm 3 , Saturation 85%, 75%, 60%, 55%, 50% configure five soil samples with different moisture content. The compacted specimens were prepared by the method of stat...

Embodiment 3

[0078] The undisturbed soil samples and disturbed soil samples of expansive soil were collected on the Baise Expressway in Guangxi, and the basic physical property indexes and engineering property tests were carried out. The indoor test results show that the plasticity index of the expansive soil sample of Baise Expressway is 33.5%, and the free expansion rate is 63%. According to the current expansive soil identification and classification standards for highways, the soil samples taken are medium expansive soils. Adopt a kind of expansive soil direct shear test device and shear strength test method of the present invention, sample preparation is carried out to Guangxi expansive soil and carry out direct shear test, concrete implementation steps are as follows:

[0079] According to the initial dry density of 1.60g / cm 3 , Configure ring knife soil samples with saturation of 95%, 90%, 85%, 80%, and 75%. The disturbed soil specimens were prepared by statically pressing samples...

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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 ...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): G01N3/24G01N3/02
Inventor 张锐赵旭郑健龙蔡树生兰天龙明旭
Owner CHANGSHA UNIVERSITY OF SCIENCE AND TECHNOLOGY
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