Abstract:
The revitalization of Newark, New Jersey included construction of large mixed- use residential towers. The developer previously completed a 35-story building in the downtown area adjacent to the recently developed Prudential center and supported the super structure on driven steel H-piles. The H-piles were driven to depth of approximately 40 feet below the ground surface and designed to bear in the underlying bedrock with a design capacity of 200 tons. The developer was seeking construction of a new 31-story building less than one mile from the previous construction site with assumption that driven H-piles would be sufficient for support of the proposed structure. After completion of a site-specific geotechnical investigation, it was determined that bedrock was encountered at depths ranging between 168 feet and 182 feet below the ground surface.The overburden soils included glacial deposits that consisted of relatively loose to medium dense sand overlying relatively soft silt and clay and a lower stratum of medium dense sand. The geotechnical recommendation included installation of drilled displacement piles as an alternative to traditional driven H-piles. The pile contractor proposed installation of tapered tube piles and calculated a design capacity at a depth of approximately 70 feet to achieve a capacity of 200 feet. PDA testing of the tapered tube test piles revealed capacities that were much less than the required capacity. Therefore, the developer elected to proceed with the recommended drilled displacement piles. The following paper details in-situ pile test results which provided a beneficial alternative to traditional driven pile solutions.