针对交通荷载循环应力水平低、循环次数大的特点,利用英国GDS公司生产的振动三轴仪在不同固结围压、不同循环应力比下对温州原状饱和软黏土进行了大周数(50 000次)不排水循环加载试验,研究了循环应力比对饱和软黏土应力-应变曲线、回弹模量和累积应变的影响.研究表明:循环应力比对饱和软黏土应力-应变曲线的形状及其发展规律影响明显.相应地,随着循环应力比的增大,回弹模量的衰减程度加大,达到稳定所需的循环次数增多.通过对50 000次循环后的回弹模量和累积应变进行分析,发现循环应力比在0.60-0.70是一个临界应力水平,当循环应力比大于该水平时,回弹模量不随循环应力比的变化而改变,达到"渐近线刚度";而累积应变则开始迅速增长,变得不稳定.
Considering the characteristics of traffic loading,undrained high-cycle loading(50 000cycles) triaxial tests under different initial confining pressures and cyclic stress ratios were conducted on natural Wenzhou soft clay through dynamic triaxial test system(DYNTTS)manufactured by global digital system(GDS)corporation in England to research the influences of cyclic stress ratio on stress-strain curves, resilient modulus and permanent strain.Results show that cyclic stress ratio significantly influences the shape of stress-strain curve and its development.Accordingly,with the increase of cyclic stress ratio,both the decreasing degree of resilient modulus and the cycle number reached steady value increase.By analyzing the resilient modulus and permanent strain after 50 000cycles,the new cyclic stress ratio(in the range of 0.60-0.70)is suggested as a critical stress level.When the cyclic stress ratio is larger than this level,the resilient modulus reaches a constant value called"asymptotic stiffness"while the permanent strain increases rapidly.