This paper presents experimental results from a study 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 and the results compared against controls where no fluid had to
be displaced by the concrete. Normal pile surfaces were investigated. Additionally, the
situation of “soil caked” piles was also investigated. Both model and full-scale tests
were conducted. In the model tests, twenty eight 15 cm square prestressed sections
were used with the embedment depth varied between d-2d, where d is the width of the
pile. In the full-scale tests, 16 specimens were tested. The prestressed piles were 36 cm
square with the embedment varied between 0.5d-2d. Four of the sixteen piles were cast
with embedded gages located at the top, middle and bottom of the interface region.
The results showed 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.
Keywords: seal slab, cofferdam, bond, concrete, bentonite, salt water, full-scale,
prestressed, pile, foundation.
Author: Gray Mullins, Ruben Sosa, Rajan Sen & Moussa Issa, University of South Florida
Publisher: DFI