Shaking table test on accumulation of excess pore water pressure in silty sand ground subjected to repeated liquefaction histories

Silty sand seabed deposits may experience repeated liquefaction during offshore earthquake sequences, posing a threat to marine infrastructure. Modeling tests offer an effective way to reproduce the dynamic response of saturated deposits under seismic loading. Previous shaking table tests, however, have mainly focused on the dynamic response during the first liquefaction event. To address this gap, a series of shaking table tests were conducted in this study on sands with different fines, subjected to five sequential seismic excitations. The repeated liquefaction response and excess pore water pressure ratio ( r u ) of silty sands were analyzed under sequential shaking. Then, an index of shear strain rate disturbance (SRDI) is proposed to describe the net macroscopic shear response during vibration. The results indicated that an increase in fines content ( FC ) changes the pattern of r u development, leading to a longer duration of elevated pore pressure and a lower net macroscopic shear response during the mainshock. Furthermore, regardless of the content of fines, all specimens exhibited progressively weaker net macroscopic shear response as the repeated shaking progressed.