Comprehensive Load Test on Prestressed Concrete Piles in Alluvial Clays and Marl in Savannah, Georgia

Abstract

This paper introduces a comprehensive full-scale pile load test program on 457-mm (18-in.) square prestressed concrete (PSC) piles in Savannah, Georgia. The program consisted of pile driving analyzer testing during initial pile driving and restrikes, Statnamic tests, static axial compression load tests, and reciprocal lateral load tests. On the basis of the interpretation of the test data, some important findings were obtained: (1) the alluvial clays in Savannah can only provide very limited resistance; (2) the time-dependent pile capacity gain after pile driving (i.e., setup effect) was approximately proportional to the pile embedment length into the Marl formation; (3) the estimated equivalent static pile capacities from the Statnamic tests were comparable to those from the static axial load tests; (4) the Marl formation is a competent bearing stratum for piles; (5) the potential degradation of pile concrete stiffness caused by pile driving should be accounted for in pile capacity analysis; and (6) the piles exhibited stiffer response under the monotonic lateral loading condition than the cyclic lateral loading condition. Finally, predictions on both axial and lateral pile capacities, using the soil parameters derived from the instrumentation data and back-analysis of the pile load tests, were compared with the corresponding pile load test results. The comparisons demonstrate that in combination of the static-bearing capacity formulas and the LPILE program, the developed soil models can make reliable predictions on both the vertical and lateral behaviors of the PSC piles driven through the soft alluvial clays to end bearing in the Marl formation.