关于直剪试验若干问题的讨论

Discussion on Some Disadvantages of Direct Shear Test

岩土体的抗剪强度是岩土工程实践中一个重要参数,而直剪试验是确定岩土体抗剪强度最常用的方法之一。基于数值模拟和室内试验探讨了直剪试验存在的若干问题。研究发现,剪切速率对直剪试验的影响主要表现在排水条件上;方形试样中剪切位移对剪切带有效面积的影响略小于圆形试样;剪切过程中,法向应力和剪应力的变化会引起应力在时空分布上的不均匀性,会导致试样内主应力发生偏转,并通过数值模拟验证了该结论。该研究结果对直剪试验的改进和修正提供了较好的依据。

The shear strength of rock and soil is an important parameter in geotechnical engineering practice,direct shear test is one of the most commonly used methods to determine the shear strength of rock and soil. Based on numerical simulation and experiment,the problems of direct shear test are discussed. It is found that the effect of shear rate on the direct shear test is mainly reflects in the drainage condition. The influence of the shear displacement on the effective area of the shear zone is slightly smaller in square specimen than that of the circular. In the shear process,the change of normal stress and shear stress leads to the nonuniformity of the stress in the spatiotemporal distribution,which leads to the deflection of the principal stress in the specimen,and the numerical simulation is used to verify the conclusion. The results of this study provide a good basis for the improvement and correction of the direct shear test.