Philadelphia Phoundations Â– Where have we been? Where are we going?-PPT Presentation

PPT Presentation

Pdf Summary

The presentation describes a drilled-shaft load-testing program for Philadelphia’s Schuylkill Riverwalk project, where foundations had to be installed in highly variable Wissahickon Schist near active rail infrastructure.<br /><br />The original design called for 5–8-foot-diameter shafts with rock sockets up to 20 feet long. Borings and probes revealed weathered and fractured rock, making capacity difficult to predict. Two full-scale tests were conducted at challenging locations: one used a two-stage bi-directional test to measure rock-socket side resistance and end bearing; the other tested high-capacity end bearing in a competent rock layer surrounded by poorer rock.<br /><br />The tests measured end-bearing capacities of 867 and 990 ksf, with rock side-shear results varying by location. These findings supported a more efficient foundation design: shaft diameters were reduced to 3 and 5 feet, socket lengths were shortened to a maximum of 10 feet, and the design incorporated measured rock resistance. Reinforcement and construction inspection procedures were also adapted to the revised design and equipment.<br /><br />The program enabled rapid design decisions and helped release part of the site soon after testing. Construction required specialized drilling equipment, casing, obstruction removal, and work in restricted-clearance areas beside operating rail lines.<br /><br />The document also includes background on Philadelphia’s history and geology, followed by PennDOT examples of foundation and geotechnical challenges in the region. These include complex geology, karst, rockfalls, and space and traffic constraints, addressed through approaches such as jet grouting, lightweight fill, stone columns, and column-supported embankments.

Keywords

drilled-shaft

load testing

Wissahickon Schist

rock socket

bi-directional test

end bearing

side resistance

foundation design

Schuylkill Riverwalk

geotechnical engineering