Numerical Simulation And Deformation Analysis Of Deep Foundation Pit Support Excavation At Changfeng South Road Station

With the rapid development of China's urbanization,urban underground rail transit and underground space structure have also been greatly developed.In the engineering practice,the accident of deep foundation pit engineering appears continuously,the foundation pit collapse,the collapse of the enclosure structure and the large-scale subsidence of the ground caused the significant economic loss and the human casualties.Therefore,it is very necessary to discuss the supporting theory of deep foundation pit,monitor the construction site,study the influencing factors of foundation pit deformation and the finite element numerical simulation.On the basis of the theoretical research on the support and deformation of deep foundation pit,combined with the deep foundation pit engineering of Hefei Metro Station,this paper studies the deformation of the retaining structure,the ground settlement around the foundation pit and the heave of the bottom of the pit during the excavation of the deep foundation pit by using the method of combining the field monitoring data analysis with the numerical simulation of the finite element software MIDSA GTS NX.The influence of the parameters on the deformation of foundation pit is studied,which can provide reference for the future engineering.The following contents are studied in detail:(1)On the basis of consulting the relevant literature and research results at home and abroad,the deformation of deep foundation pit and the status quo of finite element analysis are summarized.The supporting methods of common foundation pit and the design calculation theory of supporting structure are studied.Several common deformation principles of foundation pit deformation are summarized,and the common calculation methods of deformation are introduced.(2)The monitoring data of deep foundation pit deformation of Changfeng South Road Station are analyzed.It is found that the ground settlement and horizontal displacement of pile top increase with the depth of foundation pit excavation.When the foundation pit reaches a certain stability,the deformation gradually stabilizes;the deeper the soil excavation,the level of retaining pile.The larger the displacement increases,the more stable the foundation pit is.The excavation process of foundation pit was numerically simulated by the finite element software MIDSA GTS NX.Through the analysis of the calculation results,it was found that the ground settlement around the foundation pit was grooved,and the maximum value appeared about 9 meters away from the foundation pit;the uplift of the bottom of the foundation pit increased with the depth of the foundation pit excavation,which was large in the middle and small around.The deformation of retaining structure changes from cantilever to parabola gradually,and the maximum value appears in the middle and upper part of retaining pile.(3)By changing some parameters of the retaining structure of the foundation pit,it is found that the deformation and ground settlement of the retaining structure of the foundation pit increase with the increase of the rigidity of the retaining structure and the embedded depth,but when the foundation pit reaches a certain stability,the deformation does not change,indicating that the rigidity and embedded depth of the retaining structure have an impact on the foundation pit.The displacement of the top of the retaining structure is mainly affected by changing the position of the first support.The maximum displacement of the retaining structure always appears under the excavation surface.In practical engineering,the depth of the first support should be paid attention to.