Response of Saturated Sands to Cyclic Shear at Earthquake Amplitudes

Both quasi-static and resonant cyclic shear tests were performed on hollow cylindrical specimens of saturated sands at various densities and confining stresses. Shear moduli measured at nondestructive amplitudes were shown to be independent of frequency for the range of 0.1 Hz to 50 Hz. Application of cyclic shear at larger amplitudess caused effective stress to decrease and failure. The number of cycles to failure was related to the ratio of cyclic shear stress to maximum drained shear stress. Effective confining stress reduces approximately linearly with number of cycles. Shear modulus and shear damping can be described by the Hardin-Drnevich equations if change in effective stress is properly adjusted. Procedures were developed to use research results in analyzing soils in dams or other profiles to predict factor of safety against liquefaction failure and to estimate shear modulus and damping of soils for subliquefaction conditions when these soils are subjected to earthquakes.