椭圆应力路径下双向非等幅剪切对软黏土动力特性的影响

Effects of bi-directional unconstant amplitude shear stress on dynamic properties of soft clay in under ellipse stress path

针对地震产生的S波引起土体水平剪切振动问题,以温州软黏土为研究对象,采用多向循环单剪仪进行了12组应力控制下的不排水循环单剪试验,研究了水平双向耦合荷载作用下循环应力比β和双向剪切应力比η对饱和软黏土动力特性的影响.通过对试验数据回归分析,建立了软黏土的软化指数模型.试验结果表明:软黏土动强度与η呈近似线性增长关系.β一定时,η越小,土体产生的剪应变和孔压越大.当β=0.14时,剪应变、孔压发展缓慢,呈稳定型增长,η对软化指数、剪应变和孔压的影响不大;当β≥0.20时,剪应变、孔压发展迅速,呈破坏型增长,η的减小明显加快了剪应变、孔压的发展及软化指数的衰减,从而使软黏土更容易发生软化.

Aiming at the problem of horizontal shear vibration caused by S-wave in earthquake, 12 groups of stress controlled undrained cyclic simple shear tests were carried out using multi-directional cyclic simple shear apparatus by taking Wenzhou soft clay as the research object. The effects of the cyclic stress ratio β and the bi-directional shear stress ratio η on the dynamic properties of saturated soft clay under horizontal bi-directional coupled loads were investigated. The softening index model of soft clay was established through analysis of data regression. The test results show that the relationship between the dynamic strength of soft clay and η is nearly linear.When β is constant, the smaller η, the greater the shear strain of soil and the pore pressure. When β=0.14, the strain and the pore pressure develop slowly and exhibit a stable growth, and the change of η has little effect on the strain, the pore pressure and the softening index . When β≥0.20, the shear strain and the pore pressure develop rapidly and exhibit a destructive growth, and the decrease of η accelerates the development of the shear strain and the pore pressure and the attenuation of the softening index, making soft clay more vulnerable to softening.