A laboratory study on the pore pressure generation model for Firouzkooh silty sands using hollow torsional test

This paper discusses the applicability of a simple model to predict pore water pressure generation in non-plastic silty soil during cyclic loading. Several Stress-controlled cyclic hollow torsional tests were conducted to directly measure excess pore water pressure generation at different levels of cyclic stress ratios (CSR) for the specimens prepared with different silt contents (SC=0% to 100%). The soil specimens were tested under three different confining pressures (σ'3= 60, 120, 240 kPa) at a constant relative density (Dr=60%), with different silt contents. Results of these tests were used to investigate the behavior of silty sands under undrained cyclic hollow torsional loading conditions. In general, beneficial effects of the silt were observed in the form of a decrease in excess pore water pressure and an increase in the volumetric strain. Modified model for pore water pressure generation model based on the test results are also presented in this paper. Comparison of the proposed pore pressure build up model with seed’s model indicates the advantage of proposed model for soil with large amount of silt.