Geotechnical Assessment of the Manhattan Cruise Terminal Piers: Analysis of Timber Piles in Soft Organic Silts-PPT Presentation

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The geotechnical assessment examined Manhattan Cruise Terminal Piers 88, 90, 92, and 94, with detailed analysis focused on Pier 88. Built in 1934, Pier 88 is supported by about 2,500 timber piles driven through very soft organic silts and clays. Earlier borings showed these soils generally extend to bedrock, with occasional sand layers near the offshore ends of the piers.<br /><br />Investigations included standard penetration testing, laboratory soil tests, and sonic/ultrasonic testing of 32 timber piles. The nondestructive tests indicated an average pile length of about 70 feet. However, capacity calculations suggested that an equivalent 100-foot pile length would be needed to achieve the historical design capacity of 18 tons. The assessment therefore considered the possibility that piles had been spliced or fitted with timber fins—features the sonic tests might not detect. The report cautions that sonic testing was not effective for determining pile capacity; parallel seismic testing or full axial load tests could provide better estimates.<br /><br />Analyses evaluated pile bearing capacity, axial and lateral behavior, and settlement. A single pile’s estimated allowable capacity was 18 tons, reduced to about 11.75 tons when group effects were considered. Soil-spring curves were developed for use in structural modeling.<br /><br />Consolidation settlement for a typical pile cluster was estimated at about 15 inches, with approximately 95% consolidation expected since the pier’s construction. Deposited soils above the original mudline may also cause negative skin friction, adding an estimated 6 inches of downdrag settlement. Combined settlement was therefore estimated at roughly 21 inches, consistent with generally uniform settlement observed on site.<br /><br />The structural model broadly agreed with the geotechnical estimates, but identified locations where current loads exceed pile design capacity and may cause excessive settlement. These loads are associated with additions, renovations, and maintenance over the pier’s lifetime.

Keywords

Manhattan Cruise Terminal

Pier 88

geotechnical assessment

timber piles

soft organic silts

pile capacity

sonic testing

consolidation settlement

negative skin friction

structural modeling