Pile-Driving Mechanics at the Base as Informed by Direct Measurements

Abstract

Determination of the base contribution to total pile capacity is an important aspect in the design of end-bearing piles. For driven piles, dynamic load testing and signal matching are the predominant approach for estimating total pile capacity. This includes separating the base and shaft resistance, and differentiating between static and dynamic contributions. Despite its widespread usage, the approach is susceptible to uncertainty and nonuniqueness of solutions. The new instrumented Becker Penetration Test (iBPT) configured as a reusable test pile (RTP) is capable of directly measuring the dynamic pile response at the base and along the shaft during driving. In this paper, RTP measurements at the base are presented and used to guide the selection of models and parameters available in signal-matching methods. The direct measurements at the base depict pile driving as a steady penetration process with unload–reload cycles, and consistency of locked-in residual force between subsequent blows. The results show that when fundamental mechanical constraints are satisfied, simple existing models are adequate for capturing the measured response, and uncertainty and nonuniqueness at the base are curbed.