上海软土动剪切模量衰减规律的试验研究

为了获得上海软土在循环动力荷载作用下的动力特性，特别是动剪切模量的衰减规律，采用原状第④层上海软土进行等向固结不排水动三轴试验，分析了加载频率和动应力比 对动剪切模量的影响。试验结果表明，对于上海第④层软土，动应力比达到0.2时，土样才发生破坏；土样的剪切模量-累积轴应变曲线不受加载频率和动应力比的影响；剪切模量的衰减下降主要发生在轴应变0～1%区间。最后提出了一个描述剪切模量衰减规律的数学模型。

Experimental investigation of degradation law of dynamic shear modulus of Shanghai clay under cyclic loading

In order to study the cyclic strength of natural Shanghai clay under cyclic loading, especially the degradation behavior of dynamic shear modulus, after sample’s isotropic consolidation, a series of undrained stress-controlled cyclic triaxial tests are conducted on natural Shanghai clay with different cyclic stress ratios (defined as , in which is the cyclic deviator stress and is the cell pressure) and different loading frequencies. The effect of dynamic stress ratio and loading frequency are investigated. According to the test results, for layer No.4 of Shanghai clays, the soil sample damage occurred until the dynamic stress ratio is 0.2. The relationship between shear modulus and strain is not affected by dynamic stress ratio and loading frequency; and shear modulus decay falling mainly in axial strain 0?1% range. For the dynamic shear modulus degradation index , it is smaller with the smaller frequency and with the larger dynamic stress ratio under the same number of cycles. Through the analysis of the effect of dynamic stress ratio and frequency on dynamic shear modulus, a mathematical model for shear modulus degradation is presented. The tests data and the model calculation are good agreement.