排水条件下卸荷土体变形特性的真三轴试验研究

在真三轴仪上模拟基坑开挖周边土体的应力路径，进行了排水与不排水两种卸荷试验，通过对试验结果的对比分析可知，土体在不同排水条件下应力-应变关系有着显著的差异，说明排水条件对土体的变形性状有一定的影响。进一步研究了排水条件下卸荷土体广义剪应力与广义剪应变的关系，证明土体广义剪应力与广义剪应变关系曲线呈明显的非线性，并根据土体实际应力路径定义了中主应力系数，推导出了土体卸荷剪切模量计算公式。

An experimental study of soilmass deformability subject to true triaxial loads during unloading under drainage

The stress-path of the soilmass surrounding the periphery of a foundation pit project during excavation is simulated using a true triaxial unit; and two kinds of unloading tests are conducted under drainage and undrainage conditions respectively. It can be known from the comparison between the testing results that there is a remarkable difference in the stress-strain relationship of the soilmass provided the drainage conditions are different, which shows that the drainage, condition has an effect to a certain degree on the soilmass’s deformability. Further studies are conducted on the relationship between generalized shear stress and generalized shear strain under drainage conditions during unloading, the results showing the nonlinear relationship of those strain and stress. Finally, the equation to calculated the soil’s unloading shear modulus is deduced when the intermediate principal stress coefficient is defined in the real stress-strain path of the soils.