Liquefaction potential of hydraulic fills

A container terminal is under construction at the Port of Barcelona. The quay, 1.6 km long, is made of concrete caissons founded on granular rubble mounds. The natural soil is a sequence of normally consolidated fine-grained deltaic deposits that reach a thickness of over 60 m. The quay was backfilled with hydraulic fill dredged from the seabed soils in front of the caissons quay, deposited by a rainbowing technique. A failure of a section of the quay was attributed to the static liquefaction of the hydraulic fill. This failure prompted a field campaign to identify fill properties and its liquefaction potential. Standard and seismic CPTU´s and Marchetti dilatometer tests were performed as well as a programme of laboratory tests. Available indices to estimate liquefaction potential were calculated and compared. One of the relevant issues raised after the quay failure was the ability of preloading to eliminate the liquefaction potential of the fill. In situ tests were performed on the fill before and after a large scale preload test. Liquefaction indices at those two stages are compared showing, in some cases, a reduction of liquefaction potential after preloading.