A Load-Testing Program on Large-Diameter (66-Inch) Open-Ended and PSC-Instrumented Test Piles to Evaluate Design Parameters and Pile Setup

Abstract

This paper presents the results from a pile load testing program for a bridge construction project at Chalmette, Louisiana. The load testing includes three 66-in. spun-cast post-tensioned open-ended cylinder piles and one 30-in. square prestressed concrete (PSC) pile driven at four different locations along the bridge site in clayey-dominant soil. Both cone penetration tests and soil borings/laboratory testing were used to characterize the subsurface soil conditions. All test piles (TP) were instrumented with strain gauges to measure the load distribution along the length of the TPs and to measure the side and tip resistances, separately. Dynamic load tests (DLT) were performed on all TPs at different waiting periods after pile installations to quantify the amount of setup (i.e., increase in pile resistance with time). Case Pile Wave Analysis Program (CAPWAP®) analyses were performed on the DLT data to calculate the resistance distributions along the TPs. A static load test was performed only on the PSC pile and statnamic load tests (SNLT) were conducted on both pile types. Design parameters such as the total stress adhesion factor, α, and the effective stress coefficient, β, were back-calculated. The α values ranged from 0.41 to 0.86, and the β values ranged from 0.13 to 0.29. The load test results showed that SNLT overestimated the tip resistance as compared with dynamic and static load tests. Moreover, the pile tip resistance was almost constant during the testing period, and setup was mainly attributed to increase in pile side resistance with time.