The Response of A “Plug” in An Open-Toe Pipe Pile

Abstract

Two published case histories are taken as reference to a discussion on how to consider the effect of soil core inside a pipe pile driven open-toe, as opposed to the response of a pile driven closed-toe. The analysis of the measurements shows that the comparison has to be made in terms of deformation, not capacity. Both piles have similar shaft resistance along the outside of the pipe. For the closed-toe pile, toe resistance acts along the full cross section. For the open-toe pile with a soft core, some toe resistance is mobilized by the force against the steel annulus. The soil force that acts at the bottom of the core, pushes the core upward much like the upper portion of a pile tested in a bidirectional test and the upward movement is resisted by shaft resistance along the inside of the pile. However, the core is very soft compared to a pile and the movement of the pile toe is quickly spent, resulting in a limited magnitude of inside shaft resistance, moreover one acting only along a limit length of the pile up from the pile toe. Recommendations for how to analyze the response of an open-toe pile are presented and a comparison is provided between the results of a simulated static loading test on a closed-toe and an open-toe pipe pile are presented, showing that the comparison—and piled foundation design—have to recognize and consider the pile toe movement during service conditions.