双向激振下饱和软黏土动模量与阻尼变化规律试验研究

 通过GDS双向动三轴系统对双向激振循环荷载作用下饱和软黏土的动模量与阻尼变化规律进行研究。结果表明：随着径向循环应力增加，孔压比增加，双向激振对孔压的影响仅限于对初始孔压的提高，且初始孔压提高的幅度近似与径向循环应力相等；双向激振对门槛循环应力比的影响不明显；径向循环应力对动模量与阻尼的变化规律有显著的影响，在动应变一定的情况下，随着径向循环应力比的增加，动模量降低，阻尼比增加。随着径向循环应力的增加，小应变弹性模量随之减小，且近似与径向循环应力比成线性关系，据此实现了Hardin公式的修正，建立了双向激振下小应变弹性模量经验模型。径向循环应力及围压对 及 关系曲线影响不明显，通过对双曲线型模型修正，建立双向激振下饱和软黏土动模量与阻尼随动应变变化的经验模型。

EXPERIMENTAL RESEARCH ON CHANGING RULES OF DYNAMIC MODULUS AND DAMPING RATIO OF SATURATED SOFT CLAY UNDER BIDIRECTIONAL EXCITING CYCLIC LOADING

Dynamic modulus and damping ratio of saturated soft clay under bidirectional cyclic loading are investigated by GDS dynamic triaxial system. It is observed that the pore water pressure ratio increases significantly with the increase of radial cyclic stress ratio. Radial cyclic stress has great effect on initial pore water pressure;and the increase of initial pore water pressure is approximately equal to the radial cyclic stress. The threshold of cyclic stress ratio changes little under bidirectional cyclic loading. The dynamic modulus and damping ratio are affected by radial cyclic stress significantly. By increasing the radial cyclic stress,the damping ratio increases while the dynamic modulus decreases. Small strain elastic modulus decreases as the radial cyclic stress increases and there is a linear relation between the small strain elastic modulus and the radial cyclic stress ratio. An empirical model for the small strain elastic modulus is obtained based on the modification of Hardin equation. The radial cyclic stress and confining pressure have little effect on the curves of - and -. By modifying hyperbolic model,the empirical models for describing the change of dynamic modulus and damping with dynamic strain are obtained.