A Performance-Based Approach to the Design of Shallow Foundations Resting on Heterogeneous Subsoil Prone to Liquefaction Hazards

Performance-based design (PBD) has become increasingly important in recent years, especially for the design of foundations rested on sub-soils that are susceptible to liquefaction at seismically active areas. Shallow foundations may fail due to excessive settlement because of liquefaction of the underlying loose saturated cohesion-less sands. Building codes usually do not address the issue of liquefaction-induced settlement of shallow foundations. In this paper, a framework is proposed for calculating the liquefaction-induced settlement of shallow foundations resting on heterogeneous two-layered liquefiable soil by conducting a series of 3D. hydro-mechanical dynamic analyses in a fully coupled manner employing an advanced constitutive model that can account for anisotropic behavior of sand and effect of soil fabric. After model verification, based on a database gathered from conducting a large number of numerical modelings regarding the behavior of shallow foundations on two-layered soil, in two cases of dense sand over loose sand and vice versa, equations are proposed for calculating the amount of the foundation settlement that occurs due to liquefaction. The proposed equations can be used either for performance-based design of shallow foundations on liquefiable soil strata, or for controlling the settlement of shallow foundations under earthquake that are designed through conventional methods.