Evaluation of the Behavior of Equal and Variable-Length Piles in Soft Clay Using Field Load Tests and Finite Element Modeling
Corresponding author: Lan V. H. Bach
Abstract
This study examines the performance of Equal-Length (EL) and Variable-Length (VL) pile groups with rigid caps under central axial loads, focusing on load-bearing capacity, load distribution, and unit shaft resistance. Small-scale loading tests are performed on both groups. The EL group consists of steel pipe piles, 60 mm in diameter and 1,800 mm long, while the piles in the VL group are estimated using Feld's rule to maintain a consistent total length between the groups. The Finite Element Method (FEM) is also used to validate the results, based on real pile groups driven in Saigon South, District 7, Ho Chi Minh City, Vietnam. The small-scale field test results show that the VL pile group achieved nearly 20% higher bearing capacity compared to the EL pile group of the same size and total pile length. The data indicate that load distribution in the EL pile group was considerably uneven, with the load on the corner pile being roughly 10% higher than on the edge pile and 31% higher than on the center pile. Conversely, the VL pile group demonstrated a more even load-distribution, with differences between piles not exceeding 10%. The FEM supported these trends, confirming the model’s accuracy in predicting load-sharing effects in complex pile arrangements and reinforcing the structural advantages of VL configurations. Additionally, the VL pile group method provides cost savings by reducing material requirements and construction time compared to traditional EL pile foundations. These findings highlight the potential of VL pile groups as a cost-effective, high-performance solution for centric load foundations in challenging soil conditions, offering improved load-bearing capacity, balanced load-distribution, and reduced construction costs.
Keywords:
load distribution, variable-length pile group, equal-length pile group, load-settlement behavior, static load testingDownloads
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