A Study on Time-Effects of Piled Raft System by Using Computational Methods

On the soft grounds, effects of consolidation on performance of the system of piled rafts as well as superstructures cannot be overlooked due to nonlinear interaction characteristics. Conventional methods of engineering design and numerical procedures of two-dimensional interaction analysis cannot realistically simulate loading and deformation mechanism of the interaction system and cannot completely predict variations of deformations and internal forces of both structure and piled raft foundation. Therefore in order to well understand long-term behavior of the interaction system, time-dependent effect of soil deformations on performance of the interaction system of piled rafts and foundations as well as superstructure is evaluated in this paper. The nonlinear deformation and strength behavior of foundation soils are taken into account by using the elasto-plastic constitutive model based on Mohr-Coulomb's yield criterion while the consolidation effect of subsoil under loading is incorporated by numerically solving the coupling Biot's equations of consolidation. Numerical analyses are conducted for the structure-raft-foundation interaction system by using the finite element methods. Based on numerical analyses for a given interaction system, both the features of variation in time of internal forces, settlements and the characteristics of compatibility mechanism of interaction system are examined. It is shown that both nonlinear behavior of soft soils and consolidation characteristics of foundation remarkably affect the time-dependent performance of the interaction system. Such dependency is intimately related to variation of excess pore water pressure of subsoil.