| The complex mechanical properties of typical soft soil layers in the pearl river delta region and the sensitive surrounding environmental conditions of deep foundation pits in urban have put forward higher requirements for the design and construction of deep foundation pits of urban subway.It is especially important to accurately simulate the complex mechanical properties of soft soil layers and the complex construction mechanical behaviors of deep foundation pits.Based on the deep foundation pit of a subway station in pearl river delta,the constitutive model of hardening soil model(HS model for short)is introduced in this paper.Through laboratory test,field test,theoretical analysis and finite element numerical simulation,the complex mechanical behavior of soft soil layer and deep foundation pit are analyzed and studied.The specific research contents and results are as follows:1.The mechanical properties of typical silty clay in the pearl river delta region under different stress path conditions were analyzed by the stress path triaxial test with the GDS instrument and the parameters of HS model were obtained from the relevant test results.Then based on the existing research,the silty clay’s parameters of HS model in different drainage conditions,different stress paths and different regions were compared and analyzed.2.Based on the key algorithm of hardening soil model which uses the explicit integral fundamental stiffness method and the secondary development function of nonlinear finite element analysis software(ABAQUS),the HS constitutive model’s subroutine is developed.Through the comparison of the conventional triaxial test and the three-dimensional finite element numerical simulation,the rationality of the UMAT subroutine is verified and the simulation accuracy of HS constitutive model versus mohr-coulomb constitutive model are comparative analyzed.3.Based on Biot three-dimensional consolidation theory,the three dimensional stress and seepage coupling analysis model is established to consider the elasto-plastic deformation and hardening characteristics of soft soil through introduce the hardening soil model.The definite condition of stress and seepage coupling analysis in deep foundation pit and the basic principle of fluid-solid coupling finite element analysis based on the platform of ABAQUS are systematically described.4.Integrate the above research results,a three-dimensional stress and seepage coupling finite element analysis model is established,with the Guicheng station of foshan metro line three as the research object,to analysis the mechanical behavior of stru in the deep foundation pit of tranfer station and the changing characteristics of surrounding environment.In the end,some reasonable suggestions to the changes of design and the accident of construction process in the deep foundation pit are put forward.The research achievement of this paper have certain reference value for comprehensively mastering the complex mechanical properties of soft soil in the pearl river delta region,perfecting the design and construction analysis theory of deep foundation pit engineering in soft soil area as well as ensuring the safety and stability of deep foundation pit engineering. |
