Model prediction of the cyclic liquefaction resistance of gassy soils

The resistance to liquefaction of soils can be significantly increased by slightly reducing the degree of saturation. Many experimental studies demonstrated that the augmented compressibility of the pore fluid mixture composed by entrapped bubbles within a continuous fluid phase reduces the amount of seismically induced excess pore water pressure. On the contrary, interpretation through constitutive models of the cyclic response of nearly saturated soils, often referred to as gassy soils, is by far less explored in the literature. This paper addresses this topic by considering the gas–water mixture as a homogeneous equivalent fluid whose compressibility has been used along with the elastoplastic constitutive model formulated by Dafalias and Manzari (2004). The model has been calibrated on the experimental data obtained from monotonic triaxial tests on saturated sandy soils and then validated with the results of cyclic triaxial tests on saturated and non-saturated liquefiable sandy soils. The selected calibration has been used to perform parametric analyses by varying the initial conditions of the soil (i.e., the relative density and degree of saturation), thus further emphasizing the beneficial effect of quasi-saturated fluid to delay the onset of liquefaction instabilities.