Experimental Investigation of Plastic Demands on Piles During Lateral Spread-Induced Loads

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Chang, Barbara J.; Hutchinson, Tara C.
Missouri University of Science and Technology
Geotechnical Engineering
conference paper description
Past earthquakes have demonstrated that lateral spreading from liquefaction of the soil may cause undesirable movement and potential failure to the below ground portion of a pile foundation. For a multi-layer soil profile, the case of a dense crust layer overlying a liquefiable soil layer may create large localized plastic demands in the piles. To study this behavior and provide detailed data for use in model validation studies, a one-g shaking table experiment was conducted considering a single reinforced concrete pile embedded in a 3-layer soil system. The model pile of 10 inch diameter was tested in a sloped laminar soil box (70 in x 154 in x 74 in) to study its response to seismic kinematic loading. Inertial load effects were isolated from kinematic effects by designing the specimen without an inertial mass at the top. The test specimen was designed at the lower bound of typical design (low strength and stiffness) to promote yielding. The pile was extended 4D (where D = pile diameter) above the ground surface and penetrated 7D into a stiff uppermost crust (2.5D thick) overlying a middle saturated loose sand layer (2.5D thick) and a lower dense layer of sand (2.0D thick). The specimen was subjected to increasing amplitude ground motions to induce liquefaction and lateral spreading loads. Results indicate significant plastic demands localized at the crust-liquefiable layer interface.