Semi-rigid piled-raft system for soft subsiding ground

Laboratory scale model tests were conducted with (a) rigid piled-raft system (RPRS) in clay and (b) model footings resting on unreinforced and reinforced granular fill overlying reconstituted Ariake clay with or without floating piles. A reinforced granular bed (RGB) over piles in clay (RGBPC) is suitable in subsiding environment. It can deform in accordance with that of the subsiding ground and behave as a semi-rigid piled-raft system (SRPRS) in clay. In the case of RGB on clay (RGBC) or RGBPC, the reinforcements in the fill improve its stiffness, by virtue of which the loads from the footing get spread through the fill onto a larger area on the surface of the clay, thereby reducing the settlements. The piles in the case of RGBPC help to further improve the load carrying capacity (or Bearing Capacity Ratio, BCR) and reduce the settlements.