考虑软化特性的软黏土动应力-应变关系研究

针对在地震、波浪、交通等循环荷载的作用下饱和软黏土残余孔隙水压力上升，从而导致软黏土刚度、强度发生软化的这种现象，对循环荷载作用下考虑循环软化特性的饱和软黏土动应力-应变进行了研究.以往的研究大多忽略初始偏应力对软黏土循环软化及动应力 应变关系的影响.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，研究了循环次数、循环应力水平、初始偏应力对饱和软黏土刚度软化及应力 应变关系的影响.试验结果表明，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和初始偏应力的施加都将加快刚度软化和累计塑性应变的发展，从而加速土体的破坏.同时，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，利用该公式并结合修正的Masing准则对软黏土的动应力-应变关系进行描述.

Study on dynamic stress-strain relationship of soft clay considering degradation of stiffness under cyclic loading

Earthquakes,storm waves and traffic often induce severe undrained cyclic loading.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 and dynamic stress-strain relationship of soft clay.The degradation of stiffness characteristics and dynamic stress-stain relationship of normally consolidated soft clay subjected to undrained cyclic triaxial loading were investigated at different numbers of cycles,cyclic stress levels and initial deviator stresses.It was observed that the stiffness reduces due to the increasing number of cycles,and that higher cyclic stress level and initial deviator stress accelerate the degradation of stiffness and the development of accumulated strain.A linear relationship was obtained if secant shear modulus was plotted against numbers of cycles on a semi-log scale.This relationship were synthesized in the form of an empirical equation,which was further used to describe the dynamic stress-strain relationship of saturated soft clay according to modified Masing's rule.