Design and Construction of New Shiploader Foundations within Existing Post-Tensioned Wharf in Region of High Seismicity

A new export facility required the installation of three new, fixed 2,000 tph grain shiploaders at an existing wharf. The site is located within a high seismicity zone with liquefiable soils. Each shiploader foundation was constructed as an independent structure from the existing wharf, which was expected to undergo significant damage and lateral displacements in a seismic event due to liquefaction. The locations of the new shiploaders required cutting the existing post-tensioned concrete deck to fit new foundation piles and provide a gap between the structures to minimize pounding during seismic activity. The existing wharf was also modified to introduce seismic fuses such that it could experience localized failure without impacting the new foundations. Each shiploader has a self-weight of approximately 600 t, and their foundations consist of a concrete deck atop vertical steel pipe piles. The geotechnical analysis software FLAC was used to estimate a maximum displacement of 1.3 m at the top of the new foundation structure due to liquefaction and lateral spreading. The foundation was analyzed via SAP2000 structural analysis software. To accommodate the large lateral displacement demands, a heavily reinforced pile-plug and pile-to-deck connection was required. This paper presents the unique engineering solutions that were implemented.