Accumulation of excess pore water pressure and post-cyclic settlement of saturated soft clay subjected to multi-directional cyclic simple shear

This paper is to investigate the effect of cyclic shear direction (or phase difference) on the accumulation of excess pore water pressure during cyclic shear and on the recompression after cyclic shear. Several series of uni-directional and multi-directional cyclic simple shear test under undrained conditions were carried out for a normally consolidated Kaolin. It is indicated from the test results that the accumulation of pore water pressure and the post-cyclic settlement increase with the shear strain amplitude and phase difference. The change of the void ratio in recompression stage increases approximately in proportion to the logarithm of the stress reduction ratio, and is independent of shear strain amplitude, but affected by cyclic shear direction. A new estimation method of excess pore water pressure ratio and the post-cyclic settlement by using cumulative shear strain is presented. By using this shear strain parameter, the effect of cyclic shear direction on the excess pore water pressure and on the post-cyclic settlement can be eliminated.