Journal of Civil and Environmental Engineering

Behavior of Structurally Non-connected Settlement Reducing Piles under Raft Foundation

Abstract

Fekadu Wubetu Melese* and Henok Fikre Gebregziabher

Piles act as a settlement reducer in case of connected piled-raft foundation and hence decrease the settlements of the raft. The design concept of the connected piled-raft foundations is to lessen the number of piles and utilize the bearing capacity entirely. Due to significant straining actions at the pile head-raft connection, an alternative technique is proposed to disconnect the piles from the raft. A Granular layer (cushion) beneath the raft is incorporated. The disconnection has a beneficial effect on reducing axial load compared to connected piles. For small piled rafts, non-connected piled rafts show less stiffness than connected piled rafts, and the soil is highly stressed and shows greater raft settlement. In the case of the large piled raft, non-connected piled rafts show greater settlement efficiency. However, as compared to the non-connected piled raft, the connected piled rafts show a significant reduction in raft settlement as pile spacing increases. The results show that the load transfer mechanism in a nonconnected piled raft is mainly governed by the thickness and stiffness of the cushion layer and by the stiffness of the subsoil.