Experimental–Numerical Analysis of the Ultimate Lateral Capacity of PHC Piles

Abstract

This study investigates the ultimate lateral behavior of prestressed high-strength concrete (PHC) piles in layered ground conditions at a thermal power plant site in Nhon Trach, Vietnam. Full-scale free-head lateral load tests were conducted on single PHC piles with diameters of 300, 400, and 500 mm, and the measured load–displacement responses were used to calibrate a three-dimensional finite element model in Plaxis 3D. The calibrated model reproduced the experimental H–u curves with good agreement and was further used to examine the effects of soil stratification and head boundary conditions. Comparison with the Japanese Road Association (JRA) analytical approach shows that JRA provides conservative displacement predictions for the larger-diameter piles (D400–D500) over practical displacement ranges, while the agreement improves for D300 at larger deformations, reflecting the stronger influence of the underlying soft clay and the limitations of equivalent-soil idealizations in layered profiles. Normalized head displacements at maximum test loads fall within u/D≈0.06–0.13, consistent in order of magnitude with reported full-scale lateral pile tests in the literature. The results support using JRA for rapid screening, whereas calibrated 3D numerical analysis is recommended for working design and for translating free-head test outcomes to fixed-head or pile-group boundary conditions in similar layered ground settings.