中文摘要：

循环荷载作用下，软黏土将发生软化现象，而以往的研究中大多未考虑初始偏应力的影响。通过对萧山正常固结饱和软黏土进行应力控制的循环三轴试验，研究了循环荷载作用下土体的刚度软化情况。通过分析每一次循环过程中割线剪切模量的变化规律，探讨了循环次数、循环应力水平、初始偏应力对刚度软化的影响。结果表明，随着循环次数的增加，土体刚度逐渐减小；循环应力水平的提高，初始偏应力的施加将加快刚度软化。在试验的基础上推导了反映土体刚度软化规律的经验公式，得到了萧山软黏土的破坏刚度比。

英文摘要：

Degradation of stiffness and strength will occur in soft clay under cyclic loading because of the generation of pore pressure. Unfortunately, previous work rarely incorporated the effect of initial deviator stress on cyclic degradation behavior. In this paper, the degradation of stiffness characteristics of normally consolidated soft clay subjected to undrained cyclic triaxial loading are investigated at different numbers of cycles, different cyclic stress levels and different initial deviator stresses. The influence of these three factors on the shear stiffness is investigated by analyzing the secant shear modulus in each unload-reload loop. It＇s observed that the stiffness reduced with progressive number of cycles. On the other hand, higher cyclic stress level and initial deviator stress accelerate the degradation of stiffness. A linear relationship is obtained if secant shear modulus is plotted against numbers of cycles on a semi-log scale. This relationship has been synthesized Xiaoshan soft clay is obtained from the equation.