Combined Effects of Lateral Spreading and Superstructure Inertia-PDF

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The report examines how superstructure inertia and liquefaction-induced lateral spreading combine to affect pile foundations. It analyzes a shake-table test of a reinforced-concrete pile in sloping, layered sand, where shaking liquefied the saturated soils and produced about 0.4 m of permanent downslope ground displacement.<br /><br />Large pile strains developed after liquefaction began, with critical responses at shallow and deeper depths. Near the surface, strong upslope inertial loading was opposed by downslope pressure from the nonliquefiable crust, indicating that inertia and crust loading acted out of phase. At a deeper location, large strains coincided with downslope inertial loading, but the crust exerted almost no load. Soil movement had created a gap in front of the pile, and the pile moved into this gap during downslope cycles, eliminating crust pressure.<br /><br />The pile eventually formed a plastic hinge at its base and experienced excessive deformation. The report’s assessment of load interaction focuses on the response before this failure.<br /><br />The findings suggest that inertial and kinematic demands may interact differently depending on loading direction and location along a pile. In particular, the absence of crust loading during some downslope inertial cycles is a possible design scenario, alongside scenarios in which inertia and lateral-spreading loads are combined. Because the conclusions come from a single test, depend on its specific soil, pile, and shaking conditions, and do not account for crust side-shear contributions, the authors emphasize that load interaction is site- and project-specific and requires further study.

Keywords

superstructure inertia

liquefaction

lateral spreading

pile foundations

shake-table test

reinforced-concrete pile

sand liquefaction

ground displacement

pile strains

plastic hinge