Loading transfer mechanism of a piled raft subjected to normal faulting in sand

Although different kinds of foundations have been investigated against an earthquake faulting, the interaction between pile group and dip-slip fault has not yet been fully understood. This letter investigates the interaction between piled raft and normal faulting by means of centrifuge and numerical modelling. In centrifuge test, a piled raft was simulated with a half model for a better observation of fault rupture path under the raft. The loading transfer mechanism was further examined using a three-dimensional finite difference software (FLAC3D). The measured and computed results showed that the piled raft displaced and tilted linearly with the magnitude of faulting. The fault rupture bifurcated into two and diverted towards both edges of the raft. Two types of loading transfer mechanism were identified during faulting. Working load transferred from the raft to the underneath piles, and also from the piles on the side of the hanging wall to the piles on the footwall side, resulting in compression failure of the piles on the footwall side.

Assessing the effect of governing parameters of bearing capacity determination of small piled rafts on clay soil

In the present study, a small piled raft foundation has been simulated numerically through PLAXIS 3-D software. The objective of this study was to investigate the effect of governing parameters such as pile length, pile spacing, pile diameter, and number of piles on the settlement and load-bearing behavior of piled raft, so as to achieve the optimum design for small piled raft configurations. An optimized design of a piled raft is defined as a design with allowable center and differential settlements and satisfactory bearing behavior for a given raft geometry and loading. The results indicated that, with increase in pile length, pile spacing, pile diameter, and number of piles, both the center settlement ratio and differential settlement ratio decreased. The load-bearing capacity of piled raft increased with increase in pile length, pile spacing, pile diameter, and number of piles. Furthermore, the percentage load carried by the piles increased as the pile length, pile spacing, pile diameter, and number of piles increased. The bending moment and shear force in corner pile are noted to be more, and they decreased towards the center pile. With increase in pile length, the maximum raft bending moment decreased, whereas the maximum shear force in the raft increased. Further, with increase in pile spacing, pile diameter, and number of piles, the maximum bending moment and maximum shear force in the raft increased. The optimum parameters for the piled raft foundation can be selected efficiently with the consideration of maximum bending moment and maximum shear force while designing the piled raft foundation. Thus, the results of this study can be used as guidelines for achieving optimum design for small piled raft foundation.