Experimental study on behaviors of piled foundation with connected and disconnected piles

Field model tests are performed on the rigid pile composite ground(RPCD),the conventional piled raft(CPR) and the piled raft with gap between pile top and raft(PRGPR) to study the raft-pile-soil interaction with different structural connection forms between the pile top and the raft.The settlement of raft,soil beneath the raft and soil surrounding the piles groups at different depths under different load levels are measured.Also,the axial forces of the pile and the raft-soil contact pressure are recorded through the whole loading process.Based on the analysis of the measured data,the load transfer mechanism and settlement characteristics of piled raft concerned are studied.Compared with the working behaviors of RPCD and CPR,the test results show that the working behaviors of PRGPR are quite similar to those of RPCD before the raft and pile top are contacted.However,it will start to work similarly to CPR after the raft and pile top are contacted.The different connection forms between the pile top and raft can significantly affect the compaction of soil among piles and thus can affect the slip at the interface between the piles and surrounding soil.For piled raft with each of the three types of raft-pile top connection respectively,the PRGPR will yield the largest pile end penetration and the CPR will yield the smallest.