One Dock Street: A Multi-Scope Geotechnical Challenge in the Heart of Philadelphia-PPT Presentation

PPT Presentation

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One Dock Street is a 31-story, 364-foot concrete residential tower in Philadelphia’s Society Hill/Old City, adjacent to the Delaware River and I-95. The development includes 272 rental units, underground parking, and a rooftop pool.<br /><br />The site presented challenging ground conditions, including a high groundwater table, former buried stream deposits, Trenton gravels, and chemically weathered Wissahickon Schist. Subsurface materials ranged from urban fill and marsh deposits to alluvial soils and decomposed or altered rock.<br /><br />The building foundations used augered cast-in-place piles. Design requirements included 340-ton compression capacity, with tension and lateral capacity required at some locations. Testing included an O-cell axial load test to 1,800 kips (2.6 times design load) and a free-head lateral test to 40 kips to calibrate the LPILE model for fixed-head design.<br /><br />Excavation support was needed for underground parking and an 11-foot-thick mat beneath the tower core. The selected system was a 16-foot-high cantilevered soldier-pile and timber-lagging wall, alongside underpinning for an existing hotel.<br /><br />Underpinning plans initially called for pits to support six hotel footings, with tiebacks providing additional lateral restraint. Timber piles were found beneath the first three footings but not the remaining three. A soil-nail and shotcrete wall was proposed between the pile-supported footings.

Keywords

One Dock Street

Philadelphia

Society Hill

Old City

residential tower

augured cast-in-place piles

groundwater

underpinning

soldier-pile wall

O-cell load test