有效自重压力下预固结的三轴不排水试验

Undrained triaxial tests with pre-consolidation under effective overburden pressures

在我国的一些有关基坑工程的规范中,对于饱和软黏土地基的抗剪强度,规定采用"有效自重压力下预固结后的三轴不排水试验"确定,原位地基土处于静止土压力状态(K0状态),而常规三轴试验是各向等压固结,这种各向等压固结压力与原位的K0状态固结压力如何对应,以使强度指标一致,是本文讨论的问题。文中根据剑桥模型的物态边界面的概念和模型的加卸载准则,得出了二者的平均主应力应当相等的结论,这对于在设计中正确确定和选用强度指标是十分重要的。

In some Chinese standards about foundation pit,it is stipulated that the shear strength of saturated soft clay is determined by undrained triaxial tests with pre-consolidation under effective overburden pressures.However,the stress state of soil in situ is K0 stress state and the consolidation stress in triaxial tests is hydrostatic pressure.In order to get the same shear strength,the two stress states have to be compared to each other.In the paper,on the basis of the conception of state boundary surface and the criteria of loading and unloading in Cam-clay model,the conclusion is indicated that the consolidation stress in triaxial tests should be equal to the mean principle stress p of soil in situ,which is very important for the proper determination of the strength index in the design.