Study on the Single-Pile Uplift Bearing Capacity Characteristics of Expanded-Disc Piles Based on FDM Numerical Simulation

Concrete enlarged-head piles, as a novel variable-section pile type, exhibit significantly superior bearing capacity compared to conventional straight-bore piles. To systematically investigate the influence of enlarged-head quantity on vertical uplift bearing capacity, this study employs a combined approach of laboratory model testing and numerical simulation. Finite Difference Mesh (FDM) models were established for straight-bore piles, single-enlarged-head piles, and double-enlarged-head piles to elucidate their mechanical behavior. Results indicate: Computational outcomes from the numerical simulation method demonstrate excellent consistency with model testing, validating the reliability of simulated results. The enlarged-head structure exhibits a markedly significant enhancement effect on pile foundation uplift bearing capacity, with the ultimate bearing capacity of single-head and double-head piles reaching 1.5 times and 2.5 times that of straight-bore piles respectively, highlighting the more pronounced strengthening effect of the double-head configuration. Under ultimate conditions, the shear slip planes of the upper and lower discs interconnect to form a continuous composite failure surface, fully utilizing the shear strength of both inter-disc and disc-top soils. In summary, the finite difference numerical model accurately replicates the complex interaction mechanisms between pile foundations and soil, providing reliable technical support for studying pile-soil interaction principles and quantifying the soil reinforcement zone around enlarged-disc piles.