Study On Construction Mechanical Behavior And Construction Method Of Large Shallow Buried Excavation Subway Station

The subway has the characteristics of large traffic volume,convenience,and less pollution,and it is fast and punctual during operation.Therefore,it has gradually become one of the important measures for the government to solve urban traffic jam.In the process of urban subway construction,subway stations often have the characteristics of large cross-section,shallow depth,difficult construction,complicated mechanical properties,and long construction period.This article takes the wulidian subway station of Chongqing Metro Line 9 as the backing project,summarizes the characteristics of the common construction methods of the subway station,and combines the design of the both side heading method to analyze the impact of the design parameters on the construction.Combined with the actual situation on site,the rapid construction method of both side heading method was proposed,and its construction parameters were analyzed.The main research contents and results of this article are as follows:(1)It Summarizes the characteristics of construction method of large-section tunnel,and analsys the mechanics stepwise mechanism of large section tunnel excavation method.The displacement of the surrounding rock,the stress and the stress of the supporting structure by using three construction methods of three-step method,CRD method and double-wall guide pit method are analyzed respectively.By comparison and analysis,it can be seen that the both side heading method is more conducive to controlling the deformation of the surrounding rock,and the stress state of the surrounding rock and the supporting structure are better.(2)The influence rules of the three design parameters of temporary vertical brace curvature radius,steel frame spacing and shotcrete are studied.The larger radius of curvature of the temporary support is helpful to control the deformation of the surrounding rock and give full play to the force of the temporary support.The smaller spacing of the steel arch is conducive to controlling the deformation of surrounding rock and reducing the stress of the supporting structure.The Thicker shotcrete is beneficial to control the deformation of surrounding rock and improve the stress of surrounding rock.(3)Combined with the actual engineering situation and the requirements for speeding up the construction progress,the rapid construction method of both side heading method is proposed.It by adjusting the excavation sequence,remove the upper core soil in advance and add vertical to strengthen temporary support.Then,further analyze the deformation of surrounding rock caused by construction,stress of supporting structure and stress of surrounding rock.And compared with the double-wall guide pit method to verify the rationality of the double-side rapid construction method.(4)After analyzing the construction parameters of the rapid construction method of both side heading method,it is found that reducing the upper row of left and right guide pits has little effect on the deformation of the surrounding rock.Therefore,it is recommended to consider reducing the upper row of cross pits during construction.The larger the excavation length,the greater the deformation of the surrounding rock.The longer the length of a single disassembly,the greater the increase in vertical deformation caused by disassembly.Reasonable excavation footage and dismantling length should be selected in combination with on-site monitoring data.