Analysis of Raft with Composite Pile through Finite Element Modelling-Paper

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The study uses three-dimensional finite-element modelling in ABAQUS to examine composite piled raft foundations, combining long concrete piles with shorter cement–fly ash–gravel (CFG) piles. The researchers modelled the raft and piles as elastic materials and the clay soil as elasto-plastic, using the Mohr–Coulomb failure criterion. The model was checked against two experimental studies, with numerical and measured load–settlement results differing by less than 10%.<br /><br />Six pile configurations were analysed under vertical pressures of 100, 300 and 500 kPa. The study compared settlement and pile stresses, and also assessed the effect of a cushion layer beneath the raft. Configuration P-1, with uniform-length piles, produced the smallest settlements and the highest raft stiffness. P-6 had the largest settlements and lowest stiffness. However, P-3 was identified as a practical, economical composite arrangement: its stiffness was about 19% lower than P-1, while requiring less concrete.<br /><br />For uniform-length piles, corner piles carried the greatest axial stresses; in non-uniform composite configurations, stresses were highest in central piles, indicating uneven load distribution. Peak axial stresses generally occurred at a depth of about 0.25–0.3 times the pile length. Adding a cushion layer increased settlement in some configurations but reduced the proportion of stress transferred to the pile tips.<br /><br />The authors conclude that P-3 is a promising balance of settlement control and construction cost. They note that further work should investigate load sharing between raft and piles, negative skin friction, and broader design guidance.

Keywords

ABAQUS

finite element modeling

composite piled raft

CFG piles

settlement analysis

Mohr-Coulomb criterion

load distribution

axial stress

cushion layer

pile configuration