Fault rupture modification by blocky inclusions

Subterranean fault rupture has been responsible for many recorded instances of building damage during past earthquakes. Differential displacement in the ground can cause shearing in overlying structures and can leave buildings in an unsupported condition. As the demand for land use increases, it may be necessary to adopt strategies to protect certain key structures from fault-related damage. This paper presents the results of an investigation of one potential mitigation scheme, that of providing rigid inclusions in the soil beneath the structure. Theoretically, the blocks should split the fault so that the fault expression at the surface is not a single surface scarp but a more gradual profile, with the effect of reducing the risk of the building being damaged either by rupture emergence along the length of the foundation or by excessive rotation. Modelling of a simple footing above a uniform sand is performed using both discrete element modelling and centrifuge model testing. While the numerical model demonstrates that blocks may be beneficial, the centrifuge tests were unable to demonstrate any splitting of the main rupture plane. However, the block mass was sufficient to increase local stresses and guide the fault. Based on this, it is concluded that while blocks may be capable of deflecting faults the method is too unreliable to be recommended without further supporting research.