Liquefaction performance of shallow foundations in presence of a soil crust

Liquefiable soils are currently categorized by all seismic codes as extreme ground conditions where, following a positive identification of this hazard, the construction of surface foundations is essentially allowed only after proper treatment soil. This article examines to what extent this situation may change in presence of a non-liquefiable soil crust, between the foundation and the liquefiable soil. Means are provided for analytical evaluation of the degraded bearing capacity and the associated seismic settlements for the specific case of strip foundations on a cohesive (clay) crust. Furthermore, the conditions are explored which ensure a viable performance-based design, and the issue of a critical soil crust thickness, beyond which liquefaction effects are minimal, is addressed.