抗剪强度是决定岩土工程中地基、边坡等土体和结构稳定性的重要力学参数, 一般通过直剪或三轴试验获取. 这类试验常采用 3∼4 个试样测定土的黏聚力和内摩擦角, 但多个试样的差异性会影响结果准确性. 基于此, 在常规直剪仪器的基础上进行改进, 使其可针对一个试样反复剪切, 获取样品的抗剪强度参数, 由 Mohr-Coulomb 包络线得到土的黏聚力和内摩擦角, 并将压实土的固结排水多级直剪试验与常规直剪试验结果进行对比. 结果表明, 多级直剪试验抗剪强度略小于常规直剪, 内摩擦角误差在 ±2.5◦. 该固结排水多级直剪方案可以用来评估压实黏性土抗剪强度.

Shear strength is an important mechanical parameter that determines the stability of soil and structures, such as foundations and slopes. Its value is generally obtained via direct-shear or triaxial tests. In these tests, three or four samples are typically used to measure the cohesion and internal friction angle of soil; the differences among samples will inevitably affect the accuracy of the results. Hence, this study improves the conventional direct-shear instrument so that it can be used to obtain the shear strength of a sample via repeated shears as well as the cohesion and internal friction angle of soil using the Mohr–Coulomb envelope. The results of multistage direct-shear tests for the consolidation drainage of compacted soil are compared with those of conventional direct-shear tests. The results show that the shear strength obtained from the multistage direct-shear test is slightly lower than that obtained from the conventional direct-shear test. Additionally, the error for the internal friction angle is ±2.5◦, which verifies that the multistage direct-shear scheme of consolidation drainage can be used to evaluate the shear strength of compacted soil.