Seismic performance of end-bearing piled raft with countermeasure strategy against liquefaction using centrifuge model tests

摘要

This paper presents the results of centrifuge model tests conducted on piled raft foundations in liquefiable soils to investigate the performance of drainage techniques as a liquefaction countermeasure method. Two series of centrifuge tests were conducted on 2 x 2 end-bearing piled raft foundations with and without drainage wells in multilayer soil deposits. The results indicate that the drainage well systems significantly reduce the foundation settlement, the excess pore water pressure ratio, and the time of dissipation under seismic loading by providing shortened water flow paths. Variations of the acceleration response, bending moment, and axial force of the piled raft are shown to be dependent on the type of surface layer. In Test-1-E with the liquefiable surface layer, the acceleration response, bending moment, and axial force of the piled raft with drainage systems were significantly larger than those observed in the piled raft without drainage systems during shaking. In contrary, in Test-2-E including a non-liquefiable surface layer, bending moment and axial force of piled raft in the absence of drainage wells were larger than those of the piled raft system with drainage wells. However, the acceleration response of raft in both systems was almost the same during shaking. The recorded data of the piled raft systems with/without vertical drains and the surface gravel layer (as a horizontal drainage system) are compared in details.