Parametric study of combined piled raft foundation for uniformly distributed surcharge over raft top surface

Piled raft foundations are a popular solution for supporting heavy structures on weak soils, but their design and analysis can be complex due to interaction among the raft, piles and subsoil underneath. The present study utilises finite element method to analyse the parametric dependence of ratio of average settlement (λ_avg), ratio of differential settlement (λ_diff), ratio of shear force (SFR), ratio of bending moment (BMR) and ratio of load-sharing (χ_pr), for square raft with underneath connecting circular cross section piles for uniformly distributed surcharge all over the top surface of raft. The parameters varied are spacing to diameter ratio (S/D) of 2-20, diameter of piles (D) of 0.4 m-1.6 m, length to diameter ratio (L/D) of 8, 12 and 16, pile group to width of raft ratio (W_g/W_r) of 0.15-0.9 and raft-soil stiffness (K_rs) of 0.069, 0.558 and 1.88 corresponding to raft thickness (t_r) of 0.5 m, 1.0 m and 1.5 m respectively. The results of the present study depicts that the minimum values of λ_avg and λ_avg are observed at S/D ratio of 5 (approx.), lower K_rs and larger W_g/W_r. To enhance χ_pr, smaller pile spacing (S) and larger pile length (L) are needed. Minimum SFR and BMR are achieved at lower and larger L/D ratios, respectively. The findings can be used to guide the design and analysis of pile raft foundations for a variety of applications, including high-rise buildings, bridges, and industrial structures.