Drilled Shaft Load Test Program for Approach Spans of U.S. Hwy. 82 over the Mississippi River

Near Greenville, Mississippi, sixty-seven piers along the approach structures for U.S. 82 over the Mississippi River are to be founded on groups of drilled shafts, 820 shafts total. Mississippi Department of Transportation (MDOT) chose to perform several Osterberg Cell load tests in advance of construction to refine shaft design lengths. MDOT contracted with HNTB Corporation to design the load test program, analyze the load test data, and provide axial capacity curves. Eight full-scale load tests were run in the fall of 2002. Results supported use of effective stress design methods for predicting side shear in the cohesionless and cohesive alluvial deposits tested. Use of the K_otan(δ) approach for estimating β in cohesionless deposits was also validated. Measured tip resistances in sands with gravel exceeded blowcount-based estimates. This paper summarizes design and construction of the load test program, presents side shear and end bearing test data, and describes foundation design methods adopted as a result of the program.