An Experimental Investigation of the Liquefaction Resilience of Dual Row Retaining Walls Using Centrifuge Modeling

Dual row retaining walls can be used as embankment structures and coastal defense against wave or even tsunami loads. However, their resiliency to a preceding earthquake and liquefaction of the foundation soil is not well understood. In this paper, dynamic centrifuge modeling is used to investigate the seismic response of a dual row retaining system where the walls are founded in a loose, saturated, and level deposit susceptible to earthquake-induced liquefaction. A combination of instrumentation techniques, ranging from measurements of the wall bending and displacements to the pore pressures and horizontal earth pressures acting on the walls, are used to elucidate the mechanics of the soil-structure system. The experiments reveal that the cyclic loading of PGA $0.4\mathrm{g}$ does not induce a catastrophic collapse. An understanding of the liquefaction phenomena, including shear-induced dilation and coseismic migration of the pore fluid toward a region of relative suction between the walls, is required to interpret the observed resilience of the wall-soil system to liquefaction. A ratcheting mechanism for the wall deformations, consistent with the coseismic measurements of the soil and structural response, is proposed. For the geometries tested, the findings challenge conventional conservative design recommendations, such as the need for sheet-pile walls to extend beyond a liquefiable layer to prevent the liquefaction-induced collapse of dual row wall systems.