Interaction of rigid shallow foundation with dip-slip normal fault rupture outcrop: effective parameters and retrofitting strategies

Abstract

Devastating influences of fault rupture outcrop on various geo-structures during past earthquakes have revealed the necessity of more detailed and comprehensive studies on the fault-foundation interaction. In this study, the interaction between the normal fault and shallow surface/embedded strip foundations is rigorously examined through a well-established upper bound limit analysis formulation in conjunction with the finite element discretization and linear programming technique. The adopted upper bound FELA method is shown to be efficient and cost-effective with high predictive capability, which can be easily implemented in any common computational platforms, like MATLAB. The accuracy of the adopted numerical method is first verified against some findings in the literature. Using this validated numerical approach, a comprehensive parametric study is performed to examine the interaction of the normal fault rupture outcrop with the surface and embedded shallow foundations. Accordingly, the influences of various parameters including the foundation breadth, the service footing pressure, the internal friction angle of the soil deposit, the foundation embedment depth, the fault throw and the relative distance between the fault rupture and shallow foundation, on the normal fault-footing interaction are systematically investigated and discussed. In addition, as an efficient retrofitting strategy to protect the shallow foundation against the fault outcrop, rigid mitigating barrier walls with different filling materials are proposed so as to divert the mainstream of the fault rupture and thus reduce its destructive effects on the overlying superstructures. In this regard, another parametric survey is carried out to explore the effects of wall-related geometric parameters, such as its depth, width, filling material and relative position, on the reduction of the destructive consequences of the normal fault rupture emergence at the ground surface. The results generally show that applying a rigid concrete wall with suitable height, width and distance from the foundation leads to the significant reduction in the amount of surface footing rotation subjected to normal fault rupture outcrop.