The apparent viscosity to model the behaviour of liquefied sands

Abstract

The liquefaction induced loss of soil strength and stiffness marks a change of soil state, that switches from solid to liquid. Recently, the research has revealed that when liquefaction is attained, the soil behaves as a non-Newtonian fluid. Therefore, the framework of soil mechanics cannot be adopted and then the soil behaviour should be studied using a fluid mechanic approach. Several research works highlighted the large potentiality of the apparent viscosity () as the parameter ruling both the liquefaction triggering and the behaviour of liquefied sands. Mele (2022) showed that liquefied sands exhibit a shear-thinning behavior (i.e. decreasing viscosity with increasing shear strain rate), highlighting the direct link between k and n (parameters of shear-thinning model) to the soil demand (CSR). This paper aims to confirm the proposed correlations of Mele (2022) passing from small to full scale. To do that, the results of 1D non-linear site response analysis of the well-known case study of Treasure Island (California), affected by extensive liquefaction phenomena during the 1989, have been studied and interpreted with a “viscous perspective”. The good agreement of the calibrated pseudo-plastic law with the results of the dynamic analysis confirms, the relevance of as physically based parameter for the correct modeling of the behaviour of liquefied sandy soils.

Keywords

• apparent viscosity
• liquefied soils
• 1d non-linear site response analysis