Effects of cyclic confining pressure on permanent deformation of saturated soft clay

A series of partially drained cyclic triaxial tests under different stress paths are carried out on typical Wenzhou saturated soft clay. The influence of cyclic confining pressure on the permanent deformation behavior of saturated soft clay in partially drained condition is studied. The experimental results show that: in partially drained condition, comparing the test results from conventional cyclic triaxial tests with a constant confining pressure and deviator stress cyclically shearing alone, cyclic confining pressure has great influence on both the permanent volumetric strain and permanent axial strain. Under the same cyclic stress ratio, for a given number of cycles, both the permanent volumetric strain and permanent axial strain increase with the increasing of the amplitude of cyclic confining pressure, which indicates that the conventional cyclic triaxial tests with a constant confining pressure may underestimate the settlement of subsoils induced by traffic load. Based on the permanent volumetric strain and permanent axial strain after 10 000 cycles, two empirical formulas are proposed. They can quantify the effects of cyclic confining pressure on the permanent volumetric strain and permanent axial strain during tests on saturated soft clay under the partly drained condition, and can be used to predict the permanent deformation induced by traffic load including any combination with varying deviator stresses and varying confining pressures.