Experimental and numerical analysis of the under-reamed piled ring foundation

The experimental and numerical analysis of the under-reamed piled ring foundation (with/without RDFS cushion) supported by soft clay was carried out. Total 34 model tests were performed to understand the effect of the under-reams and randomly distributed fibre reinforced sand (RDFS) cushion on the parameters like pile length, centre to centre spacing between under-reams, differential settlement, axial force in the under-ream pile and load sharing mechanism. Results have indicated that in comparison to the straight piles, under-reams at the bottom of piles significantly increases the load carrying capacity and reduce the differential settlement of the piled ring foundation. Load improvement factor for under-reamed piled ring foundation with RDFS cushion was noticeably higher, and settlement reduction ratio was lower than that without RDFS cushion. RDFS cushion increases the percentage of the load taken by the ring raft in the under-reamed piled ring foundation. The inner edge of the ring raft settled more than that outer edge and the centre. And the differential settlement of the under-reamed piled foundation with/without RDFS increased with the increase in the pile length and reduction in spacing between under-reams.