Field investigation into the performance of pipe pile in soft clay under static and cyclic axial loads

Abstract

This study presents a field investigation on the evolution of the effective stress, the shaft friction at the pile-soil interface and the pile-end base resistance of a 29.5-m-long prestressed concrete pipe pile in soft clay under static and cyclic loadings (with a large number of 50 000 cycles). The results indicate that under low-level cyclic loading (CLR ≤ 0.2; CLR refers to the ratio of cyclic load amplitude to the ultimate capacity), the pore water pressure at the pile-soil interface accumulates initially with the number of cycles, followed by gradual dissipation after reaching its maximum value. The effective stress decreases initially and then increases again. The shaft friction is observed to increase after cyclic loading. Due to axial load redistribution, the base resistance decreases with the number of cycles. When the pile is imposed to high-level cyclic loading (CLR ≥ 0.5), the pore water pressure at the pile-soil interface keeps accumulating while the effective stress continues to decrease consequently, leading to the degradation in shaft friction. The base resistance increases as a result of axial load redistribution. In particular, the effects of the static load level and the cyclic load level on the variations of shaft friction are analyzed.

Analysis of Soil Response during High-Frequency Vibratory Steel Pipe Pile Driving in Soft Soil

“…In soil with high water content, cyclic loading increases the pore water pressure at the pile-soil interface, causing a reduction in effective stress in soil [9,10]. It results in a decrease in shear strength and a corresponding decrease in the friction coefficient between the pile and soil [11]. Highfrequency vibration can disrupt the structure composed by particles at the pile-soil interface significantly, leading to localized stress relaxation.…”