Connected Versus Disconnected Piled Raft Systems: A Comparative Experimental Assessment

This article presents a comparative assessment of the behaviors of connected piled raft (CPR) and disconnected piled raft (DPR) systems on the basis of an experimental study. Large-scale physical model tests are performed on 2 × 2 CPR and 2 × 2 DPR foundations embedded in sandy soil under static vertical load to understand the fundamental difference in the load transfer process involved in these two geometrically different foundation systems. Test results indicate that the inclusion of granular cushion platform under the raft in case of DPR plays the pivotal role in altering its load transfer mechanism from that of the conventional CPR system. The CPR shows higher load bearing capacity as well as higher settlement efficiency as compared to DPR. However, the DPR, upon loading, exhibits completely opposite pile-raft load-sharing phenomenon than conventional CPR system as the raft is observed to take majority of the externally applied load initially and then the pile load share is found to increase gradually with settlement. In CPR, the connected piles reduce the raft stiffness, whereas, in DPR, the piles enhance the raft stiffness and act as soil reinforcements.