No abstract

When connected piles are used as settlement reducers, the proportion of vertical load carried by the pile may come close to the allowable load of the pile. To reduce not only the vertical load, but also the lateral load and bending moment to which the pile is subjected, the disconnected piled raft (DPR) has been introduced as an effective design for the role of the settlement reducers. Although several DPRs have been constructed, most of the research efforts on DPRs are limited to the structural behavior such as the evaluation of the seismic acceleration of the structure on the DPR; thus, there is a need to evaluate the dynamic performance of DPRs focusing on geotechnical problems. In this study, the seismic behavior of DPRs is investigated using dynamic centrifuge tests and compared with the results obtained from connected piled rafts (CPRs). The bending moment of piles of different materials, namely aluminum and steel, is evaluated. Results show that there is a reduction in the amplitude of acceleration of the foundation horizontal motion for the DPR compared to the CPR. The edge pile of a DPR attracts the smaller dynamic bending moment of the pile compared to that of a CPR. The dynamic bending moment of piles is predominantly governed by the soil behavior rather than the pile material. Finally, the seismic behavior of DPR was evaluated comprehensively through centrifuge tests.

Disconnected piled raft (DPR) or non-connected piled raft is a foundation approach with highly growing interest over the past few decades. This technique, where the raft is separated from the piles by interposing a load transfer platform (LTP), allows engineers to apply a much lower safety factor against structural failure compared to the piled foundations in which piles are structurally connected to the raft. Also possible damage to structural connections is no longer a design issue, and the horizontal loads can be effectively transmitted through the mobilized frictional force along the soil-raft interface. This paper aims to study the behavior and performance of DPR foundation under vertical loading through a parametric study. In this study, three dimensional finite element method (3D FEM) via Plaxis 3D has been employed to model the complex interactions of this DPR taken into account the load transfer in the LTP and along the pile. The analysis consists of the investigation of the effect of dominant parameters such as the area replacement ratio (pile area to mesh soil area), soil and pile stiffness, and the thickness and strength parameters of LTP. Edge effect resulting from the friction between reinforced soil and non-reinforced soil is also investigated. The results from parametric study have shed some light on design optimization.