College of Engineering

Piles are designed to transfer superstructure loads using positive skin friction and tip resistance while undergoing acceptable settlements. However, when liquefaction-induced soil settlement occurs, it can drag the pile downward and result in negative skin friction and drag load. In such cases, estimating the drag load and pile settlement becomes important for pile design. A series of centrifuge model tests were performed to study liquefaction-induced downdrag on piles. The tests included four heavily instrumented piles installed in two different soil layered profiles with their tip embedment zero, three and five times their diameterin the dense sand. Loads on the piles were varied to study their effect on drag load and pile settlement. Results are presented describing the mechanism behind the development of liquefaction-induced downdrag, the magnitude of drag load, and pile settlement. Finally, recommendations are made for the design of piles in liquefiable soils