饱和砂土液化后强度与变形特性的试验研究

利用GDS 10Hz/20kN双向振动三轴系统，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，说明该模型有较好的适用性。

Test study on strength and deformation characteristic of saturated sand after liquefaction

With the GDS 10Hz/20kN dynamic triaxial system, laboratory monotonic loading tests on the saturated sand after liquefaction were performed. Based on the two states of the test samples which are extensional or contractive at the end of cyclic loading, the stress-strain behavior after liquefaction and the effects from the liquefied degree and confining pressure on the undrained deformation characteristics of saturated sand are studied. It is found that post-liquefaction strain is composed of three stages such as low intensive stage, superlinear strength recovery stage and sublinear strength recovery stage if the sand is extensional at the end of cyclic loading, but post-liquefaction strain is only composed of sublinear strength recovery stage if the sand is contractive at the end of cyclic loading. The unified post-liquefaction constitutive model of the two states is proposed and parameters of the model are derived. Based on test results, the stress-strain relationships obtained by the model are coincident well with test data so that the rationality of it is confirmed.