Numerical Study on Behaviors of Vertically-Loaded Tender Net Foundations Supported by Piles

Tender Net Foundation (TNF), a kind of shallow foundation with soil improvement, has been developed for foundations of low-rise buildings on soft grounds. In the TNF, a grid-shaped soil improvement layer works as the raft foundation instead of the usual raft of reinforced concrete. The TNF is an efficient foundation to reduce the vertical displacements and volume of soil improvement compared to normal raft foundations. In this paper, numerical analyses of behaviors of TNFs supported by piles (Piled TNF) on very soft ground are carried out aiming at reducing differential displacement as well as average displacement. First, a FEM analysis of the TNF alone (Unpiled TNF) is conducted to estimate the vertical load–displacement relation to confirm that the bearing capacity is secured for vertical load of a 5-story (mid-rise) building. Then, FEM analyses of Piled TNFs supported by various combinations of pile diameters, lengths, numbers, and arrangements are conducted.