Physical and Numerical Modeling of Hybrid Foundations to Mitigate Seismic Fault Rupture Effects

Abstract

Strong earthquakes threaten civil structures through ground shaking and, sometimes, due to the outcrop of the causative fault. A number of hybrid foundation schemes that have been found helpful in protecting a structure against strong shaking are evaluated with respect to their effectiveness in reducing the impact of tectonic displacements as well. A series of physical model tests are conducted on hybrid foundations combining (1) footings, designed to provide seismic protection (isolation) through rocking, with (2) a number of belowground interventions hopefully capable of diverting the fault rupture and limiting structural distortion. Fault rupture propagation within a stratum of dense dry sand is simulated at a scale of 1:15 using a custom made 3-m-long split box. The performance of hybrid foundation systems embedded in sand is compared with that of the same footing without interventions. Finite-element modeling is also used and, after validation against experimental results, is used in a parametric study on the effectiveness of the proposed interventions and the potential optimization of their geometry.