Comprehensive group pile settlement formula based on 3D finite element analyses

In the past, formulas for the settlement of group piles considered only a few input parameters and offered only a limited approximation of the actual settlement. Nowadays, however, thanks to the fast-growing performance of personal computers, it is possible to create large 3-dimensional finite element models with a better and more reliable settlement approximation. On the other hand, 3-dimensional finite element methods for piles are not very common in practice since the required procedure is comparatively cumbersome, expensive and needs a bit more expertise. In order to address this issue, a pile settlement formula was developed in the present study based on about 120 finite element model configurations. The group pile settlement formula incorporates the dimensions of a rectangular raft, namely, the diameter, length and spacing of the piles, vertical uniform pressure, soil moduli up to five layers, ultimate pile-soil resistance, pile-tip resistance and elastic modulus of the piles. In addition to this, the average deflection rate of the raft is estimated. The reliability of the finite element model is verified through laboratory-scale group pile tests. The proposed formula is also checked against five well-documented case studies. The formula may help engineers optimize group pile configurations more efficiently by applying the quality of the 3D finite element estimation to practice.