Evaluation of pore pressure and shear strain in clay subjected to cyclic shear stress

A series of undrained cyclic triaxial compression tests has been performed on high plasticity marine clays. Testing was performed on normally consolidated and overconsolidated specimens under various combinations of overconsolidation ratio and cyclic shear stresses. At first, the effect of frequency on development of pore pressure and strain was investigated. Then, the cyclic shear strain amplitude was related to effective stress ratio at the peak cyclic axial stress for normally consolidated sample while it was related to modified effective stress ratio for overconsolidated sample. A semi-empirical model was proposed for evaluating the development of pore pressure and residual shear strain with number of cycles. The model successfully explained the behaviour of both normally consolidated and overconsolidated clays subjected to various cyclic shear stresses.