Shake Table Tests on Residual Deformation of Sandy Slopes Due to Cyclic Loading

The evidence of earth structure damages due to earthquakes and the need for study on relatively dense and unsaturated earth structures such as river dikes and road embankments motivated this research work. A series of shake table tests were performed in order to provide the needed experimental data for this study. During the experimental program, two types of soils, i.e. Toyoura sand and a sample from natural deposits of sandy material were used. A rectangular laminar box was mounted over a rigidly fabricated slope and subjected to horizontal shaking. Sweep tests and Swedish sounding tests were also performed in order to measure the material properties. The results of these tests show the effect of different parameters such as amplitude of cyclic loading, number of cycles, initial static shear stress, confining pressure and shear stress history (loading-unloading, over-consolidation and creep time) on shear deformation of unsaturated slopes during and after cyclic loading. The outcomes of the test results are used as a basis to develop a new single degree of freedom model of mass and nonlinear spring over a slope. Stress-strain behavior of the soil is defined as a nonlinear stiffness function of a spring. Time dependent input acceleration is considered as the base excitation and the induced inertia force is superimposed on the initial static shear stress. The numerical solution of the equation of motion of the model predicted the residual deformation of the system at the end of shaking. Several cases were analyzed and compared with the test results.