Seal-slab prestressed pile interface bond from full-scale testing

This paper presents experimental results from a study to assess the interfa ce 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 and the results compar ed against controls where no fluid had to be displaced by the concrete. Nor mal pile surfaces were investigated. Additionally, the situation of soil-ca ked piles was also investigated. Both model and full-scale tests were condu cted. In the model tests, twenty-eight 15 cm square prestressed sections we re used with the embedment depth varied between d and 2d, where d is the wi dth of the pile. In the full-scale tests, 16 specimens were tested. The pre stressed piles were 36 cm square with the embedment 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 showed that loads w ere transferred to the piles over an effective area, not the entire embedde d depth. Significant bond stresses developed even for the worst placement c ondition. Recommendations are made for revising current values in specifica tions.