多向循环剪切应力路径下地基软黏土变形特性试验研究

Experimental study on deformation characteristics of foundation soft clay under multidirectional cyclic shear stress path

针对地基软黏土动力特性,对温州软黏土开展了一系列应力控制的不排水循环双向单剪试验,研究了循环应力比与相位差对温州软黏土动力特性的影响.研究表明:相位差的增加使得应力路径从直线向椭圆进而转向圆形,应变轨迹与应力路径形状相似,应力路径影响了应变的发展;循环应力比越大,相位差越大,达到破坏应变需要的循环次数越少.并且通过回归分析,建立了破坏次数随循环应力比变化的预测公式;循环应力比的增大使得应力-应变滞回曲线的应变差值逐渐变大,相位差的增大使滞回圈的形状由S形向椭圆形转变,随着循环应力比与相位差的增大土体的软化速率逐渐增大.

According to the dynamic characteristics of soft clay foundation,a series of stress controlled undrained bidirectional cyclic simple shear tests are carried out on Wenzhou soft clay,and the effects of cyclic stress ratio and phase difference on the dynamic characteristics of Wenzhou soft clay are studied.The results show that the increase of phase difference makes the stress path from straight line to ellipse and then to circle,and the shape of strain path is similar to that of stress path,the stress path influences the development of strain;the larger the cyclic stress ratio is,the larger the phase difference is,and the fewer cycles are required to reach the failure strain.Through regression analysis,the prediction formula of failure times with cyclic stress ratio is established.The increase of the cyclic stress ratio makes the strain difference of the stress-strain hysteresis curve gradually larger,and the increase of the phase difference makes the shape of the hysteresis loop change from S-shaped to elliptical.With the increase of the cyclic stress ratio and phase difference,the softening rate of the soil gradually increases.