Driven Pile Resistance Gain with Time – Evaluation of Pile Load Tests: A Case Study

ABSTRACT: The Ministry of Transportation of Ontario (MTO) invested in a static pile load test during the detailed design of the Highway 400/Essa Road overpass replacement in Barrie, Ontario, to determine the axial resistance of the test pile and to evaluate the strength gain with time. The static pile load test supported optimization of the foundation design, which ultimately included 312 HP 310x110 piles of lengths ranging from 30 to 35 metres, as well as development of acceptance criteria to control the installation of production piles. The test pile achieved a relatively low ultimate geotechnical resistance on initial driving, with negligible increase during restrike. However, the static pile load test demonstrated an appreciable improvement over a multi-week period, with the ultimate geotechnical resistance increasing by approximately 150% and 210% after 38 days and 70 days, respectively. Significant cost and schedule savings were realized in the use of higher geotechnical resistances in the pile design based on the load test data.