Abstract: Taking samples of silty clay existing distinctively in Wuhan District, a simulation experiment on true triaxial test, on which the stress path around foundation pit acts is carried out in order to obtain results of consolidated undrained test under plane strain condition. What’s more, this paper turns those results into the stress-strain curves, pore water pressure-vertical strain carves, and coefficient of intermediate principal stress-vertical strain carves, as well as a graph that describes stress path in the unloading test. The conclusions are drawn based on the above mentioned experimental results as follows: the condition that vertical pressure( ) remains constant and lateral unloading( ), the stress-strain curve would change from strain hardening to strain softening with the increase of consolidation pressure. Under lower consolidation pressure the curve shows dilatation, while under higher consolidation pressure shows an initial positive dilatation and then follows with dilatation; the intermediate principal stress( ) would slightly be superior to the minor principal stress( ). By means of defining the value of bd, the coefficient of intermediate principal stress shows stabilization. The deflection of effective stress path occurs with the increase of consolidation pressure. All these would lay a foundation for a further study on the effects of intermediate principal stress that caused to clay.

Key words: true triaxial test, plane strain, unloading, stress-strain relation