Pile-Group Response to Large Soil Displacements and Liquefaction: Centrifuge Experiments versus a Physically Simplified Analysis

The paper presents a physically simplified method for computing displacements and structural forces on piles under conditions of lateral spreading triggered by the large seaward displacement of a harbor quay wall. The method avoids the empirical selection of stiffness- reduction factors and the associated use of p-y curves that current state-of-the-art methods use. Instead, the three-dimensional (3D) highly nonlinear problem is approximated in two steps, both involving two-dimensional (2D) plane-strain analyses. The first step involves a vertical (representative)sliceinwhichthepilegrouphasbeenomittedandthat,shakenatitsbase,givesthepermanentdeformationofthequaywalland of the liquefiable soil. It is an effective stress analysis. In the second step, a horizontal (representative) slice taken from the middle of the liquefiable zone is subjected to an outward quay wall displacement; the goal is to evaluate the reduction of the pile displacement over the free- field one and the ensuing pile group distress. The pile resistance to ground deformation depends heavily on the constraints imposed by the superstructure, as well on the exact stiffness of the soil layers. Thus, the interplay between soil piles-quay wall under soil flow conditions is capturedinaphysicallymeaningfulway.Thepredictionscomparewellwithresultsfromtwocentrifugetests.DOI:10.1061/(ASCE)GT.1943- 5606.0000759. © 2013 American Society of Civil Engineers. CE Database subject headings: Spread foundations; Pile groups; Soil liquefaction; Soil-structure interactions; Experimentation; Displacement; Computation.