Study of piled and disconnected piled raft system with raft foundation in cohesionless soil

Abstract

In order to deal with the geotechnical problems and with reference to the structural point of view, there arises a concept of combination of shallow and deep foundation i.e. combination of raft and pile foundation where the piles could be both connected and disconnected from the raft known as piled raft foundation (PRF) and disconnected piled raft foundation (DPRF). In this experimental study, analysis was done on raft, piled raft and disconnected piled raft under vertical loading by varying the compactness of cohesionless soil as loose and medium density and the thickness of cushion. The geotechnical parameters such as the bearing capacity and the settlements in foundation were analyzed. It is observed that the bearing capacity in DPRF and PRF was increased 38% in loose; 74% and 75% in medium compactness sand respectively when compared to raft foundation. Settlements were also reduced to 44% in DPRF in medium compactness of soil for raft size 150x150 mm with pile length of 200mm. The optimum cushion thickness in DPRF was achieved where H/B=0.34. Thus, to meet the stability requirements of high-rise buildings, structures built in weak soils and to resist horizontal loading, the DPRF which is effective and economical can be employed.