Numerical Simulation Of Excavation And Support Of Deep And Large Foundation Pit Based On HS Model

In view of the large scale of foundation pit in soft soil area and the fact that most deep and large foundation pit projects are close to sensitive structures,the requirement of deformation control is more and more strict.In this case,in order to protect the surrounding environment,the supporting structure of deep and large foundation pit must not only satisfy the hard condition of its own strength,but also consider the influence of space-time effect caused by excavation on the deformation of deep and large foundation pit.However,due to the limitations of traditional analytical methods and relevant norms,it is difficult for most of them to accurately analyze the influence caused by space-time effect.Therefore,in a deep and large foundation pit project,it is the most important to find a reasonable analysis method and seek the optimal design scheme of foundation pit support.In this paper,the deformation behavior caused by excavation of deep and large foundation pit in soft soil is systematically studied based on the HS model finite element analysis.The main contents of the work are as follows,and corresponding conclusions have been reached:1.Based on the existing relevant information such as the Geological Survey report,the characteristics of the project,the surrounding environment and the selection of the supporting system are analyzed,and the calculation method of the deformation of the deep foundation pit is discussed.2.The applicability of HS model is analyzed,and the physical and mechanical properties of the soft soil are tested in laboratory.In this paper,the E50 REF and Eurref of HS model are determined by indoor conventional triaxial test,and the calculation parameters are provided for the following three-dimensional simulation analysis.3.Using the MIDAS / GTS finite element software under the condition of HS model,two-dimensional and three-dimensional models are established to simulate the whole dynamic process of the excavation of the deep foundation pit of the fourth-phase deep foundation pit project of Alibaba Xixi,the optimum support scheme is analyzed.4.Through the finite element method,the whole dynamic process of the construction scheme of the earth excavation with the consideration of space-time effect is simulated,and the final simulation results of deep and large foundation pit are analyzed and compared.By comparing with the whole earth excavation scheme without considering the space-time effect,it is concluded that the effect of space-time effect on the excavation of deep and large foundation pit is significant and should be fully considered in the design and construction stage.5.on-site monitoring of the excavation of the deep foundation pit,relying on the fourth phase of the deep foundation pit project of Alibaba Xixi,a lot of monitoring results have been obtained,such as displacement of deep soil,horizontal displacement and settlement of top beam,axial force of support,settlement of column pile,settlement of ground around foundation pit,settlement of Shallow Foundation around foundation pit and construction of Pile Foundation.Based on the monitoring data,the deformation characteristics of deep foundation pit in soft soil during excavation are analyzed.6.Comparing the deformation of 3D numerical simulation with the actual monitoring results,the deformation curves of the two points are very similar and have the same change law.This is mainly because the three-dimensional numerical simulation is the ideal state of foundation pit excavation,and can not fully consider the existence of various construction factors,so the comparison of actual test results results of the numerical value is small.But it is still enough to verify the practicability and accuracy of the finite element analysis based on HS model,which is very helpful to the simulation of deep and large foundation pit excavation.