A numerical study on the seismic behaviour of cantilever embedded retaining walls in saturated sand

Field observations during past earthquakes have shown that quay walls may experience severe damages if positive excess pore water pressures develop in the retained or foundation soil, leading to a reduction of the shear strength and stiffness of the soil or, in extreme cases, to liquefaction. A reliable numerical prediction of seismically induced excess pore water pressures requires the development of a dynamic fully-coupled formulation capable of reproducing solid-fluid interaction together with the adoption of advanced constitutive models. This work presents a numerical study on the dynamic behaviour of cantilever retaining walls embedded in saturated sand. The advanced constitutive model SANISAND, together with an element using a fully-coupled u-p dynamic formulation, were implemented in the finite element code FEAP v8.4. The main goal of this work is to investigate the effects of the soil relative density, of the presence of the water table and of the frequency content of the earthquake on the overall seismic response of the wall. The work indicates that different failure mechanisms can develop within the soil-wall system, depending on the amount of excess pore water pressure build-up in the foundation soil. The numerical results are commented with reference to some experimental observations from two small scale dynamic centrifuge tests on a pair of embedded cantilever walls in saturated sand.