中文摘要：

为研究上海第4层软土在循环荷载作用下的动力特性变化规律,采用原状土进行室内动三轴试验,分析不同动应力比和频率对上海第4层软土动强度的影响。试验结果表明：对于上海第4层软土,其剪切模量与应变关系曲线几乎不受动应力比和频率的影响;剪切模量的下降主要发生在应变0-1%阶段;由于应变速率效应的影响,高频率时试样破环所需的循环次数要大于低频率时;动应力比达到0.2时土样才发生破坏;在土的不同应变阶段,频率对应变增幅的影响效果不同。

英文摘要：

To study the strength of Shanghai soft clay under cyclic loading,a series of dynamic triaxial tests were conducted with different dynamic stress ratios and frequencies.According to the test results,the relationship between the shear modulus and strain was not affected by the dynamic stress ratio and frequency.When the strain was set to 2%,the shear modulus decreased slowly but significantly.The sample cyclic time with high frequency was larger than that with low frequency.With the Shanghai soft clay,soil sample damage phenomenon occurred until the dynamic stress ratio reached 0.2.The frequency had different effects on the growth of the strain in different strain stages.