Rigid slab foundation subjected to strike–slip faulting: mechanisms and insights

Abstract

In this paper, the interaction of rigid slab foundations with a strike–slip fault is studied. A three-dimensional finite-element model of the soil–foundation system is developed, employing a thoroughly validated constitutive model that incorporates strain softening. The widely used rigid box type boundaries are compared to periodic boundaries, demonstrating their superiority. Allowing the soil to deform freely, periodic boundaries allow realistic simulation of fault rupture propagation through soil and minimisation of parasitic boundary effects. An approximate dimensional formulation is presented and verified by comparing the response of two self-similar systems. A parametric study is conducted, revealing two distinct kinematic mechanisms: a rotational one, where the foundation mainly rotates; and a translational one, where the foundation either displaces parallel to the fault trace or remains almost stationary. It is shown that the response is controlled by the presence of the foundation, acting as a kinematic constraint, which can be quantified by its polar moment of inertia, Iz. The rotational mechanism leads to positive bending moments of larger magnitude, whereas the translational leads to negative moments of larger magnitude. The effect of key dimensionless parameters is parametrically investigated, including the fault rupture location, the surcharge load, the interface friction coefficient and the foundation aspect ratio. Shorter foundations (parallel to the fault trace) tend to rotate, whereas longer ones tend to displace. Fault rupture locations close to the foundation sides lead to translation, whereas locations close to its centreline lead to rotation. The development of the translation mechanism is facilitated by the increase of surcharge load and interface friction coefficient.