Finite element modelling for piled raft foundation in sand

This study relates to the analysis of un-piled and piled raft foundations with sandy soil conditions similar to those found in Surfers Paradise of Australia. The subsoil layer model was established for Surfers Paradise from 25 boreholes data at four different sites. The boreholes extend to 50m from ground surface to the rock stratum. A seven layer subsoil model was established and the geotechnical parameters for these layers are estimated from SPT tests. Based on these geotechnical parameters, a finite element analysis was conducted on un-piled and piled raft foundations. For the unpiled raft, the normalized settlement parameter (IR) for the raft sizes of 8m×8m and 15m×15m ranged as 1.02-1.15, and 0.64-0.81 respectively. In the case of the piled raft with raft thicknesses of 0.25, 0.4, 0.8, 1.5 and 3m, the corresponding maximum settlements are 64, 63.3, 62.6, 62.3 and 62.2 mm, and the bending moment values are 107, 160, 321, 446 and 485 kNm. The piles are 0.7m diameter and 16m length. Three values of intensity of loading as 215, 430 and 645kN/m are studied. The suitability of piled raft foundation in sandy subsoil is assessed and general conclusions are made.

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