DFI Journal - The Journal of the Deep Foundations Institute

Volume 13, Issue 1, January 2019
DOI: 10.1080/19375247.2019.1592893

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Modified Strong Rock P-Y Curves for Rock-socketed Pile Shafts (RESEARCH PAPER)

Arash Khosravifar, Ph.D., P.E., and Zia Zafir, Ph.D.


"The original strong rock (SR) p-y curves for rock-socketed shafts exhibit a brittle response where the postpeak resistance drops to approximately zero. This brittle response could result in a progressive failure of the p-y curves in the rock which, in turn, results in excessive pile lengths to provide required lateral stability to sustain large seismic and lateral loads. This paper proposes a modification to the strong rock (SR) p-y curves where the post-peak residual strength is set to 20% of the ultimate lateral soil/rock resistance (0.2 x pult). This residual resistance is proposed based on the assumption that the post-peak lateral resistance of cracked rock is not smaller than the lateral resistance of heavily weathered rock estimated from the weak rock (WR) and Liang et al. (2009) p-y curves. The effectiveness of the initial stiffness of the SR curves is evaluated against the results of three lateral load tests on 6-ft-diameter rocksocketed shafts. The modified SR curves are compared against back-calculated p-y curves from the lateral load tests."

rock-socketed shaft; p-y springs; lateral load test; pile