YU Yongtang,ZHU Jianmin,ZHENG Jianguo,et al.Study on Deformation and Strength Characteristics of Xi'an Loess by Borehole Shear Tests[J].Journal of Disaster Prevention and Mitigation Engineering,2022,42(05):1104-1112.
YU Yongtang,ZHU Jianmin,ZHENG Jianguo,et al.Study on Deformation and Strength Characteristics of Xi'an Loess by Borehole Shear Tests[J].Journal of Disaster Prevention and Mitigation Engineering,2022,42(05):1104-1112. DOI: 10.13409/j.cnki.jdpme.20210606001.
Study on Deformation and Strength Characteristics of Xi'an Loess by Borehole Shear Tests
In order to reveal the deformation and strength characteristics of loess in the process of Borehole Shear Tests (BST), the normal displacement sensor and shear displacement sensor were installed in the traditional borehole shear instrument, and the modified borehole shear instrument was applied to the BSTs at different depths in a typical loess stratum, Xi'an. Meanwhile, undisturbed soil samples were taken from the adjacent exploration well for triaxial consolidated undrained shear tests, and consolidated and unconsolidated quick direct shear tests. Finally, the shear strength parameters measured by different test methods are compared and analyzed. The test results show that the relation curve of normal stress versus normal displacement can be described by the penetration-compaction stage, quasi-elastic deformation stage, and plastic deformation stage. The shear failure process under the first normal pressure goes through the short-term elastic stage and the long-term elastic-plastic stage until it reaches the relatively stable shear strength. The shear failure process under the increments of normal pressure goes through the elastic stage when the shear stress increases from zero to the proportional strength, the elastic-plastic stage when the proportional strength increases to the peak strength, and the yield failure stage when the peak strength decreases to the residual strength. When the normal stress is in the range of quasi-elastic deformation stage, there is a good linear relationship between the shear stress and the normal stress, which conforms to the Mohr-Coulomb strength criterion; The internal friction angles measured by BSTs are generally higher than those of triaxial consolidated undrained shear tests, consolidated and unconsolidated quick direct shear tests, but the cohesions are lower than those of triaxial consolidated undrained shear tests and direct shear tests except that it is higher than that of direct shear tests in shallow stratum (within 10 m depth).
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