Parametric analysis of the effects of stress relief on the performance and capacity of piles in nondilative soils

Abstract

To provide support to superstructure and substructure, piles are often installed beneath a deep basement prior to its excavation. However, the effects of stress relief on the performance and capacity of piles due to deep excavation are rarely reported in the literature. In this study, two different types of pile load tests were simulated with and without considering excavation effects by conducting parametric axisymmetric finite element analyses. The first test was a pile load test on a sleeved pile from the ground surface prior to deep excavation, and the other is a load test on an unsleeved pile at the final excavated level. It is found that an excavation could reduce the pile capacity by up to 45% and pile stiffness by up to 75%. The effects of stress relief due to an excavation increase with normalized excavation depth (H/L) and excavation radius (R/H). Moreover, the maximum tension induced in a pile by excavation varies with H/L, and it has a peak value when 1 < H/L < 1.25. The value of maximum tension increases with the pile–soil modulus ratio (Ep/Esm). When Ep/Esm = 100, peak tension develops at 0.5H. On the other hand, tension reaches a peak at 0.7H when Ep/Esm = 20.