Testing device and method for true cohesive force of clay

Abstract

The invention provides a testing device and method for a true cohesive force of clay. The testing device comprises a water tank, wherein a clay sample to be tested is arranged in the water tank; a porous plate is placed on the upper end surface of the clay sample; and vertical displacements of the porous plate are measured through a dial indicator. The measuring method comprises the following steps: preparing the sample according to regulations for highway geotechnical tests; carrying out placement and submerging saturation on the sample; applying overlaying loads until the sample is damaged,obtaining the maximum main stress sigma<1> on the sample through measurement, and measuring an inclination angle theta of a shearing surface when the sample is damaged; and determining coordinates ofa Mohr's circle according to the Mohr-Coulomb theory, drawing the Mohr's circle, and drawing a tangent line B passing through an intersection point a of a straight line, which passes through an original point and of which the inclination angle is theta, and the Mohr's circle, wherein an intercept of the tangent line B on the Y axis is the true cohesive force of the clay sample. The device and method provided by the invention has the advantages of high simplicity, high convenience in operation and high reasonability in structure; and the true cohesive force of the clay in a status without a confining pressure can be obtained, so that the long-existing problem in the field that the true cohesive force of the clay cannot be accurately obtained for slope stability calculation is solved.

Description

technical field [0001] The invention discloses a test device and a test method for clay true cohesion, and belongs to the technical field of geotechnical engineering and geotechnical testing. Background technique [0002] Clay is one of the main types of soil, widely distributed in the shallow surface of the earth. Engineering problems of clay slope instability are often encountered in the construction of highways, railways, buildings, and water conservancy projects. Different from sand and silt, because clay contains clay minerals such as montmorillonite, illite or kaolinite, and has a large clay content, its shear strength includes the friction strength provided by the friction between soil particles and soil particles , also includes the cohesion generated by mutual attraction and bonding between soil particles. For the calculation and analysis of clay slope stability, cohesion and internal friction angle are the most important calculation parameters. Whether the cohes...

AI Technical Summary

Problems solved by technology

However, a large number of studies have shown that most strength envelopes are not linear in the small stress range (less than 50kPa), so it is often inaccurate to determine the cohesion by extending the straight line segment to find its intercept

In a state of relatively large stress, soil particles will experience a certain degree of embedding and friction with the sliding of the shear surface. The occlusion between the particles belongs to the shear strength described by the internal friction angle parameter, but in the process of data processing Due to the extrusion of the overlying pressure, this part of the friction force will be included in the cohesion parameter, resulting in the measured cohesion force being larger than the real cohesion force

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