OBSERVATIONS ON THE PERFORMANCE OF A PIERED RAFT FOUNDATION ON SANDY  SOIL

BURONG ZHANG and XUEYING ZHAO

ABSTRACT: Large diameter bored piers have a shaft diameter of more than 0.8 m, are man-bored and are cast in-situ. The piered raft foundation, a combination of a raft foundation with piers, has recently generated much interest and discussion as a foundation system for high-rise buildings on complicated soil conditions. This paper presents the performance of a piered raft foundation observed in-situ. The contact pressure and its distribution, the load sharing between the piers and the raft are monitored using earth pressure cells installed at the pier base-soil and raft-soil interfaces. Observation results show that the raft appears to support 20% of the building load. The substructure and superstructure have a stiffening effect on the foundation stiffness, resulting in redistribution in settlement and hence load of the piers. As a trial of the application of the research results, another piered raft foundation was successfully designed and practised for a 14-storeyed building in Shenyang, China.

Key words: bearing capacity, contact pressure, earth pressure, earth cell, pier, pile, raft, structural road, subsoil (IGC: C9/D6)