SKS02: Centrifuge Test of Liquefaction-Induced Downdrag in Uniform Liquefiable Deposit

The SKS02 centrifuge model test examined liquefaction-induced downdrag in a predominantly uniform liquefiable soil deposit. The soil profile consisted of a 1 m of coarse sand, underlain by 4 m of clay, 9 m of liquefiable loose soil, and a deeper dense soil (prototype scale). The test included two 635 mm diameter (D) piles, with their tip embedded to the depth of 0D and 5D in the dense sand layer. The model was shaken with a suite of scaled Santa Cruz earthquake motions with peak horizontal accelerations ranging from 0.025 g to 0.4 g. The model was heavily instrumented to track the development of pore-pressures, axial loads, and soil and pile settlements during and post shaking. With multiple shakings, the drag load on the piles increased and saturated at the load curve estimated from the mobilization of full negative skin friction (assuming it equal to the interface shear strength). A higher drag load was observed along the deep-embedded 5D pile as compared to the shallow-embedded 0D pile. While soil settlements were large, the piles underwent considerably smaller settlements. Most of the pile settlement (>90%) occurred during shaking and very minimal settlement (<5mm) occurred during reconsolidation.