Effect of slab stiffness on the geotechnical performance of energy piled-raft foundation under thermo-mechanical loads

Abstract

Several studies have examined the geotechnical behaviour of energy piles; however, the behaviour of piled-raft foundations containing thermal piles is not fully understood. Because piled-raft foundations are optimally designed to bear mechanical loading from the top structure, the energy piles induce extra stress and bending moments on the raft foundation (slab) from the thermal loads, which may cause structural failure. The present study evaluated the thermo-mechanical behaviour of the energy piled-raft foundations using 3D FEM to simulate the geometrical and mechanical parameters of the pile group with an emphasis on slab stiffness. The interaction between the adjacent piles in a group as well as the bending moment induced through the slab have been evaluated. The results showed that, under thermo-mechanical loads, the stiffness of the slab prevented the free expansion and contraction of the energy pile. Increasing in slab thickness from 0.2 to 0.5 m reduced the energy-pile displacement about 50%. It also was observed that a heating load induced more stress than a cooling load along the longer piles. Cooling mechanical loads caused negative skin friction in the longer piles. It was shown that the equivalent pier method is generally applicable for a group of energy piles.