DEFORMATION CHARACTERISTICS OF SILTY CLAY FROM CONTROLLED-STRESS UNLOADING TESTS

The stress-strain relationship and pore pressure characteristics are studied with stress-controlled axial shear tests. Furthermore, the determination method of deformation modulus is obtained. Two kinds of laboratory tests are accomplished under a deviator confining pressure. One is that the lateral pressure is unloaded when axial pressure maintains constant. The other is that the lateral and axial pressures are simultaneously unloaded. The test results show that the stress-strain relationship took on a hyperbolic function. Moreover, the shear strength was increasing with the increase of the lateral confining pressure. In the unloading process, with the increase of deviator stress and the strain, the soil sample took on a dilatancy trend and showed a large negative pore pressure. Besides, the undrained shear strength was increased slightly due to the negative pore pressure.