On the variation of mechanical properties of saturated sand during liquefaction observed in shaking table tests

Soil liquefaction induced by earthquakes not only causes settlement and lateral spreading of the ground, but also lowers the stiffness and strength of soil. In this paper, the variation of soil mechanical properties during liquefaction was investigated by revisiting the data of the physical model shaking table tests on saturated sand using a large laminar shear box conducted in National Center for Research on Earthquake Engineering with sinusoidal waves and the record of 1999 Chi-Chi Earthquake as input motions. The excited responses of the ground specimen during liquefaction were firstly characterized through spectrum analysis. One-dimensional shear beam idealization of the ground for wave propagation was further introduced to deduce the stress-strain relationship of the soil body. Thus, the variation of mechanical properties of saturated sand with respect to the development of shear strain and excess pore water pressure can be examined, which is beneficial to estimate appropriate soil parameters for the seismic design of foundations and to reasonably assess the seismic response of liquefied ground.