Numerical Analysis of Combined Helical Pile Raft Foundation (CHPRF) Under Compressive and Tensile Loadings

This study examines the combined helical pile raft foundation (CHPRF) performance under compressive and tensile (uplift) loadings using different configurations. The CHPRF is expected to satisfy better the settlement and the tensile capacity criteria than conventional combined pile raft foundations (CPRF). The analysis is performed in a homogenous cohesionless soil medium using the finite element (FE) analysis. The effect of various parameters, such as the diameter and the number of helix plates in a pile and the spacing between the piles, on the performance of the CHPRF is investigated. With the aid of load–displacement curves, the ultimate settlement of the CHPRF is found under compressive loadings, whereas the ultimate tensile capacity is calculated under tensile loadings. In the FE modelling, the concrete raft and steel piles are modelled with plate elements and embedded beams, respectively. The soil is assumed to follow the Mohr–Coulomb failure criterion. As per the analysis, the CHPRF exhibits less ultimate settlement and more tensile capacity compared to the conventional CPRF. The effect of the number of helices on final settlement and tensile capacity is minimal compared to the helix diameter and the spacing between the piles.