土体动剪切模量及其衰减特性现场试验研究

如何获取土体动模量原位衰减曲线是研究天然土层在循环动荷载下的动变形特性课题中亟待解决的难题。为此，本文自制了一套地震动参数现场试验系统，依据动剪切模量原位测试原理获得了不同深度土体在小应变范围内的动模量原位衰减曲线。试验数据表明:当剪应变小于4×10^－5时，土体变形处于线性阶段；当剪应变大于4×10^－5时，土体归一化动剪切模量G/G_max衰减加快，以塑性变形为主。同时，当向土层施加的垂向静荷载越大，归一化动剪切模量值G/G_max与对数剪应变值logγ_d之间的关系会逐渐上移，但直线段斜率值不变。相关成果可为试验场地的动模量取值提供一定参考。

Field experimental study on dynamic shear modulus of soil and its decay characteristics

How to obtain the in-situ decay curve of soil dynamic modulus is a pressing problem in the study of the dynamic deformation law of natural soil layers under cyclic dynamic loading. In this connection,a set of field test system for ground motion parameters was made in this paper,and the principle of in-situ testing of dynamic shear modulus was used to obtain the in-situ decay curves of dynamic modulus of soils at different depths in a small strain range. The test data shows that when the shear strain is less than 4×10^-5,the soil deformation is in the linear stage; when the shear strain is greater than 4×10^-5,the decay of the normalized dynamic shear modulus G/G_max of the soil accelerates and plastic deformation dominates. Meanwhile,the relationship between the normalized dynamic shear modulus value G/G_max and the logarithmic shear strain value logγ_d gradually shifts upward when the vertical static load applied to the soil layer is larger,but the slope value of the linear segment remains unchanged. The related results would provide a certain reference for the value of the dynamic modulus of the test site.