饱和砂土液化后强度与变形特性的试验研究

利用双向振动三轴试验装置，进行了饱和砂土液化后静力再加载试验。从砂土受振动荷载结束后所处的拉伸、压缩两种状态出发，对饱和砂土液化后的强度变形特性进行分析，研究了液化程度和围压对饱和砂土液化后不排水变形特性的影响。试验结果表明：振后处于拉伸状态的试样，液化后的变形由低强度段、超线性强度恢复段和次线性强度恢复段三段组成；振后处于压缩状态的试样，液化后的变形则只有次线性强度恢复段。提出了统一描述两种状态下砂土液化后应力应变关系的三阶段模型，并给出了模型参数的推导过程。与试验结果对比显示，该模型的预测值与试验值吻合较好，该模型有较好的适用性。

Experimental study on strength and deformation characteristics of saturated sand after liquefaction

The monotonic loading tests on saturated sand after liquefaction were carried out by using dynamic triaxial testing system. The strength and deformation characteristics of saturated sand for test samples subjected to tension or compression after cyclic loading were analyzed respectively. The effect of liquefaction degree and confining pressure on undrained deformation characteristics of saturated sand were studied. It is found that the variation of post liquefaction strain is composed of three stages, including the low intensive strength stage, superlinear strength recovery stage and sublinear strength recovery stage, if the sand is in tension state at the end of cyclic loading. Whereas, the post liquefaction strain will be sub linear strength recovery stage only if the sand is in compression state at the end of cyclic loading. The unified post liquefaction constitutive model for describing the sand in tension or compression states at the end of liquefaction is proposed and relevant parameters are deduced. The predicted results using this model are in good agreement with experimental data.