Relationship between earthquake-induced uplift of rectangular underground structures and the excess pore water pressure ratio in saturated sandy soils

The excess pore water pressure (EPWP) ratio is one of the contributing factors to the earthquake-induced uplift displacement of underground structures. To investigate its role in the incompletely liquefied soil, a rectangular underground structure buried at different depths in saturated sandy soils with different densities and under different earthquake loadings was analyzed by a numerical method. The results revealed that the uplift response was related to both the EPWP ratio and its duration, as well as the region of the liquefiable soil under the underground structure. The value of the EPWP ratio that triggers uplift fell in a range rather than remaining constant.