Effects of Cyclic Loading on Undrained Strength and Compressibility of Clay

Abstract

The effects of undrained cyclic loading on clay behaviour were investigated using triaxial tests. The current investigation is divided into behaviours during and after cyclic loading. The authors present concepts and methods for predicting both behaviours. The following conclusions were made using those methods : (1) The stress reversal observed during undrained cyclic loading accelerates excess pore pressures and residual shear strains, leading to cyclic failure. (2) Undrained strength decreases with the amplitude of cyclic-induced excess pore pressures, while post-cyclic undrained strength followed by drainage increases in proportion to the amplitude of cyclic-induced pore pressure. (3) Post-cyclic recompression volumetric strains are governed by the magnitude of cyclic-induced pore pressures. Those values can be approximately estimated using the recompression index obtained from isotropic consolidation tests.