LOAD TESTS ON DRILLED SHAFTS AT GOETHALS BRIDGE REPLACEMENT-Paper

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The Goethals Bridge Replacement is supported by more than 200 drilled shafts socketed into Passaic Formation siltstone. To verify foundation design assumptions, four shafts—two each in New York and New Jersey, with 6-ft and 9-ft diameters—underwent axial bi-directional load tests and lateral Statnamic rapid-load tests. One New Jersey shaft also received a static lateral load test to validate the rapid-load method.<br /><br />Axial tests measured unit side resistances of 30.6–36.1 ksf and unit base resistances of 319–359 ksf. These values were mobilized at relatively small displacements, and side and base resistance developed compatibly, allowing both to be combined in LRFD design. Test limits were set by the loading equipment, rather than by the shafts’ geotechnical capacity.<br /><br />A key finding was that rock quality designation (RQD) alone did not reliably predict socket performance. At a New York test shaft, rock had high core recovery but low RQD, partly because horizontally bedded siltstone and shale produced short core pieces. Despite this, the shaft developed strong side and base resistance. RQD should therefore be assessed alongside discontinuity orientation, weathering, loading direction, and socket stability.<br /><br />Lateral-test measurements were used to calibrate soil and rock p-y parameters for design. The static test showed that the equivalent-static Statnamic response closely represented static behavior, with displacement within 7% at the maximum test load. Statnamic testing also provided information relevant to rapid extreme-event loading, such as earthquakes or vessel impact.<br /><br />Overall, the testing supported the design parameters for the bridge’s rock sockets and lateral foundations, while demonstrating the value of project-specific load testing for reliable, cost-effective foundation design.

Keywords

Goethals Bridge Replacement

drilled shafts

Passaic Formation siltstone

bi-directional load tests

Statnamic rapid-load tests

axial loading

lateral load test

rock socket design

RQD

foundation design verification