Experimental study on unsaturated creep characteristics of landslide soils

Under the impacts of reservoir water level fluctuation and rainfall, the strength and deformation of slope soils, on the one hand, have features of properties of unsaturated soils; on the other hand, they exhibit time-dependent behaviour s. Therefore, it is indispensable to investigate the time-dependent behaviours of unsaturated soils to better account for the long-term stability of slopes under the effects of water. A series of suction-controlled triaxial creep tests on sliding zone soils of some landslides in Three Gorges Reservoir Area are performed. Creep curves with different values of deviator stresses and matric suctions are presented and discussed. The test results indicate that the creep strain as well as the creep strain rate at constant deviator stress increases gradually with the decrease of the matric suction. Moreover, for the increasing values of the deviator stress, a wider variation of the creep strain as well as the creep strain with suction is obtained. Then, the Mesri creep model for experimental creep strain with different suction values is established. In the model, a hyperbolic function is adopted for the stress-strain relationship and a power function for the strain-time relationship. Finally, an expression for the relationship between the suction and the initial tangent modulus <>E_d is derived. Based on this, a model of stress-suction-strain-time of specimens is developed. The comaprative results indicate that predicted results using the model are in reasonable agreement with the experimental data .