Horizontal Loading Tests on Disconnected Piled Rafts and a Simplified Method to Evaluate the Horizontal Bearing Capacity

Abstract

Disconnected piled raft (DPR) foundations have been widely adopted as an effective foundation system where the piles are separated from the raft by a granular layer, which can limit the shear forces and moments transmitted between the raft and the piles. Thus, DPR foundations may avoid the problem of horizontal forces, such as those from an earthquake or dynamic loads, which damage the structural connection between the pile head and raft. A series of static horizontal loading tests were carried out on three types of foundation models, i.e., piled raft, disconnected piled raft, and raft alone models, on fine sand using a geotechnical model in a 1 g field. In this paper, the influences of vertical loading and interposed layer thickness were presented and discussed. The results showed that most of the horizontal force was carried by raft/interposed layer friction in the DPR foundation type, and the shear force and moment of the piles were greatly reduced due to the gap between the raft and the heads of the piles. The tested foundations were simulated using a simplified method with theoretical equations derived by making several approximations and assumptions. The simulated results agreed well with the test results.

Deep Foundation Pit Excavations Adjacent to Disconnected Piled Rafts: A Review on Risk Control Practice

“…Compared with research concentration on understanding the load sharing mechanism of disconnected piled rafts [8] (Table 1), little is done on understanding the influence of excavation on nearby piled raft foundations with interposed layer. Zhu et al [173] experimentally evaluated the horizontal bearing characteristics of disconnected piled rafts. They found that the frictional resistance at the interface of mat and cushion layer provides the horizontal resistance to the applied lateral load.…”

Numerical Analysis on the Load Sharing Performance of Long‐Short CFG Pile Composite Foundation Subjected to Rotation of Adjacent Retaining Wall

“…e recent experimental study of Guo et al [17] on the pile-soil synergistic mechanism of such multipile foundation system revealed a significant influence of long piles relative to the short ones on overall settlement and stiffness of the foundation under vertical working load. In reality, however, a foundation system is not only subject to vertical loading but also to lateral loadings [18][19][20]. Ma et al [18] conducted experimental and numerical study using ANSYS software to investigate the bearing characteristics of long-short pile composite foundation subjected to horizontal forces while Zhu et al [20] studied the horizontal bearing characteristics of disconnected piled rafts with equal length piles subjected to lateral loads.…”

“…In reality, however, a foundation system is not only subject to vertical loading but also to lateral loadings [18][19][20]. Ma et al [18] conducted experimental and numerical study using ANSYS software to investigate the bearing characteristics of long-short pile composite foundation subjected to horizontal forces while Zhu et al [20] studied the horizontal bearing characteristics of disconnected piled rafts with equal length piles subjected to lateral loads. It can be seen from the results of these studies that under both vertical and lateral loads, the interposed layer plays a significant role as it adjusts the vertical load sharing while offering horizontal resistance to the lateral load by the friction developing at its interface with the other contacting materials.…”