循环荷载下饱和软黏土振后强度弱化研究

Strength degradation of saturated soft clay under cyclic loading

本文以宁波轨道交通淤泥质黏土为对象进行动、静三轴试验,探讨了不同围压、静偏应力、动应力作用下淤泥质黏土振后强度弱化规律和不排水剪有效应力路径发展规律,获得了土的强度弱化参数,结果表明:与常规不排水三轴剪切试验结果相比,振后孔压发展曲线表现出超固结土的特性,出现剪胀现象,动应力比、初始静偏应力比越大,越为明显;振后孔压累积,有效应力减小,抗剪强度随静偏应力的增大而减小,建立的u/σ3～qsd/qs线性表达式可较好地描述土的强度弱化比-归一化孔压之间的关系;随着静偏应力的增大,应力路径曲线而向左偏移,研究结果为轨道交通的动力设计提供了参考。

In this paper,the dynamic and static triaxial tests of Ningbo rail transit silty clay are carried out.The strength degradation behaviors of the silty clay and the development law of the undrained shear effective stress path under different confining pressure,static deviatoric stress and dynamic stress are discussed,and the parameters of strength degradation are obtained.The results show that the pore pressure curves behave characteristics of overconsolidated soil in comparison to the test results of conventional undrained triaxial shear,and the dilatancy occurs in the test,and increases more obviously with the increases of dynamic stress ratio,initial static deflection stress ratio. In addition,the pore pressure increases and the effective stress decreases,so the shear strength decreases with the increase of static deviator stress.The linear expression of u/σ3-qsd/qs established in this paper can describe the relationship of strength degradation ratio & normalized pore pressure of the silty clay,and the stress path curve shifts to the left with the increase of static deviatoric stress.The results can provide as a reference for dynamic design of rail transit.