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.
Highlights
Recent contributions have led to deeper understanding of the key mechanisms controlling the response of shallow strip foundations dur ing earthquake-induced liquefaction [1,2,3]
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 numerical prediction is compared to the centrifuge test results in terms of settlement and rotation of the structures, pore pressure buildup, as well as the deformation mechanisms that develop within the liquefiable layer
Summary
Recent contributions have led to deeper understanding of the key mechanisms controlling the response of shallow strip foundations dur ing earthquake-induced liquefaction [1,2,3]. [1,2,4] Such advanced constitutive models typically contain a large number of model parameters, requiring extensive soil element testing for proper calibration. Bolton et al [8], examined the spatial non-uniformity of centrifuge models through in-flight cone penetration testing They observed that the COV in terms of tip resistance, void ratio and normalized cone resistance varies between 2 and 15% in the vertical direction. The calibration is strictly based on the void ratio (e), without any effort to “fine-tune” model parameters to better match the centrifuge tests This is a first key contribution of the paper, which allows in-depth assessment of sensibly calibrated numerical simulations versus a range of centrifuge experiments. The sensitivity to uncertainties related to soil density and input motion is examined, and the effect of boundary conditions imposed by different types of centrifuge containers is identified. The quantification of the influence of lateral boundaries in function of their type and distance to the structure is considered of importance to centrifuge modellers, allowing for optimized design of future experiments, and to nu merical modellers simulating such experiments for validation purposes
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
