Soil sample eccentric compression prevention strain control type direct shearing tester

Abstract

The invention discloses a soil sample eccentric compression prevention strain control type direct shearing tester which comprises a shearing box, a vertical pressure application device, a horizontal pressure application device, a gauge and an instrument pedestal. The shearing box is formed by an upper shearing box and a lower shearing box; the instruction pedestal is provided with a limiting structure for limiting the upper shearing box to move along a horizontal pushing force direction and a rail for defining the lower shearing box to move on the surface of the pedestal along the horizontal pushing force direction; the vertical pressure application part comprises a vertical pressurization lever, a weight, a vertical pressurization frame, a pressurization rod and a pressure transfer cover;the horizontal pressure application device comprises a pusher and a steel ring; when the pusher is pushed by an external force, the lower shearing box is pushed to slide along the rail; the pushing force direction is consistent with the rail direction. According to the tester, the defect of soil sample eccentric compression of a conventional strain control type direct shearing tester is overcome,and accuracy and reasonability of strain control type direct shearing testing are improved.

Description

technical field [0001] The invention relates to the field of geotechnical engineering geotechnical test instruments. Background technique [0002] Soil is the main research object of geotechnical engineering, and its material parameters are the basis of geotechnical engineering research. The failure of soil is usually dominated by shear failure. Therefore, to determine the shear strength index of soil—cohesion (c ) and internal friction angle (φ) are particularly important. At present, there are many test methods for determining the shear strength index of soil. Among them, the strain-controlled direct shear test is widely used because of its simple test principle, easy operation and low test cost. [0003] However, the eccentric compression of the soil sample is prone to occur during the traditional strain-controlled direct shear test. The eccentric compression of the soil sample leads to uneven stress distribution in the soil, resulting in oblique shearing, which in turn ...

AI Technical Summary

Problems solved by technology

But in fact, due to the deformation of the steel ring itself due to the stress, the upper shear box will also be displaced along the shear direction, so the vertical pressure bar and the upper shear box will have a relative displacement, causing the pressure cover to deflect around the vertical pressure bar. This leads to eccentric compression of the soil sample (as shown in the figure below)

This makes part of the shear force of the steel ring test shared by the vertical pressure bar, which affects the accuracy of the direct shear test

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