Seal-Slab Prestressed Pile Interface Bond from Full-Scale Testing

In this paper, experimental results are presented from a study conducted to assess the interface bond between a cast-in-place concrete seal slab and prestressed concrete piles in cofferdams. Three different seal slab placement conditions (fresh water, salt water, and bentonite slurry) were evaluated with results compared against controls where no fluid had to be displaced by the concrete. Normal pile surfaces were also studied. Additionally, the situation of soil-caked piles was also investigated. Both model and full-scale tests were conducted. In the model tests, 28 15-cm sq. prestressed sections were used with the embedment depth varied between d and 2d, where d is the width of the pile. 16 specimens were tested in the full-scale tests. The prestressed piles were 36 cm sq., with the emdbedment varied between 0.5 and 2d. Four of the 16 piles were cast with embedded gages located at the top, middle, and bottom of the interface region. The results show that loads were transferred to the piles over an effective area, not the entire embedded depth. Significant bond stresses developed even for the worst placement condition. Recommendations are made for revising current values in specifications.