Caisson Foundations Subjected to Reverse Fault Rupture: Centrifuge Testing and Numerical Analysis

Recent large-magnitude (M>7) earthquakes have caused numerous failures induced by surface faulting, demonstrating the need to account for tectonic deformation in seismic design. Thanks to their usually high rigidity, embedded (e.g., caisson) foundations may divert the fault rupture and lead to favorable performance, whereas surface or piled foundations may fail. We present a series of centrifuge model tests to investigate the response of caisson foundations embedded in a cohesionless soil stratum, the base of which is subjected to reverse faulting. We elucidate the interplay between the propagating fault rupture and the caisson, focusing on the role of the location of the outcropping rupture relative to the caisson. The rigid-body of the caisson causes diversion and/or bifurcation of the shear localization, which is forced to develop preferentially around the edges of the caisson. The observed failure pattern and the consequent caisson response depend strongly on the exact caisson position relative to the fault. We employed three-dimensional (3D) finite-element (FE) modeling and validated it by comparing to centrifuge test results. The numerical method captures the general interaction mechanisms, showing satisfactory (if not always perfect) agreement with experiments. We then employ the validated numerical method in a parametric investigation, providing further insight into the different possible modes of foundation response.