3-D NUMERICAL ANALYSIS OF TIME-DEPENDENT BEHAVIOR OF STRUCTURE-PILED RAFT-FOUNDATION INTERACTION SYSTEMS CONSIDERING CONSOLIDATION EFFECT

摘要

In coastal areas where exists a deep layer of soft soils, raft foundations are widely employed for high-rise or multi-rise structures in order to be adapted to the soft grounds. Under such conditions, effects of consolidation of soft soil ground on performance of interaction system of rafts and foundation as well as superstructures cannot be overlooked, which display a certain nonlinear characteristics. Both conventional methods of structural design and numerical procedures of two-dimensional interaction analysis cannot realistically simulate load-carrying and deformation mechanism of the interaction system and cannot completely predict variations of deformations and internal forces of both structure and raft foundation. Therefore in order to well understand long-term behaviour of the interaction system, time-dependent effect of soil deformations on performance of the interaction system of rafts and foundations as well as superstructure is evaluated in this paper. The nonlinear deformation and strength behaviour 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 and settlements and the characteristics of compatibility mechanism of interaction system are examined. It is shown that both nonlinear behaviour 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.