Seismic Stability and Deformation of Clay Slopes

Shake table studies were used to obtain a mechanistic picture of the deformations of slopes of clay banks during earthquakes, their extent, and the factors influencing them. Simple shear tests were performed to compare the soil behavior under cyclic loading in two different conditions: (1) prototype structures in the field; and (2) laboratory-size samples. Results of these tests show that the development of a peak or yield acceleration within the slope determines whether or not deformation takes place. The yield acceleration was found to be related to the slope geometry and the clay peak strengths under seismic loading. This strength was then found dependent upon the amplitude of ground motion and rate of strain. The slope deformation was found to be a function of the residual clay strengths and the duration of the motion. Data obtained provide necessary information to relate residual strength to ground velocity and results of laboratory cyclic simple shear tests.