Shallow strip foundations subjected to earthquake-induced soil liquefaction: Validation, modelling uncertainties, and boundary effects

Abstract

Despite recent advancements in predicting the response of shallow strip foundations during earthquake-induced liquefaction, significant modelling–related uncertainties remain, which are the focus of this paper. The problem is analysed through coupled hydromechanical analyses, employing an advanced constitutive model. The model is calibrated based only on the initial void ratio, and then validated against 6 centrifuge model tests, conducted at the University of Cambridge. Through a strict validation procedure, based on pore pressures, settlement and rotation time histories, as well as deformation mechanisms, the strengths and weaknesses of the numerical model are identified. It is shown that final settlement and rotation can be predicted with adequate accuracy, but more work is needed to achieve accurate predictions of settlement rate, maximum rotation, and pore pressures in the vicinity of the foundation. The numerical model is then used to investigate key modelling uncertainties. After revealing the sensitivity to initial soil density and to parasitic vertical acceleration, the effects of the centrifuge model container and of the distance of lateral model boundaries (L) are parametrically investigated. Boundary effects are minimized with a laminar container, where a normalized boundary distance L/DL ≥ 1 is shown to be adequate for all liquefiable layer depths (DL) examined. The use of a rigid container is proven problematic, as it always imposes an unrealistic wave propagation pattern. The use of Duxseal inclusions offers a major advantage, allowing accurate reproduction of foundation settlement even with L/DL ≥ 1, a key conclusion for the design of centrifuge tests.