Study On Construction Risk Analysis And Scheme Improvement Of Square Metro Station

With the rapid development of cities in our country,traffic congestion has become one of the urgent problems in major cities.The subway’s advantages such as fast,punctual,large volume,and low pollution are prominent.Become the preferred way to relieve the pressure on the transportation system of various cities,many cities have begun to improve their subway planning and construction.As a concealed underground project,the subway is difficult to construct,has many and complicated procedures,and has a high accident rate.There are many uncertain and unforeseen risks,in recent years,subway engineering accidents have occurred frequently,therefore,carry out risk source analysis in the early stage of project construction,and improve the construction plan of important hidden danger points,help reduce the probability of risk accidents in subway projects,reduce losses caused by accidents.This article takes the construction of the square subway station of Shenyang Metro Line 3 as the research object.Summarize and learn from the predecessors on the basis of the risk analysis method of subway station construction engineering,check the site geological survey report,design,construction plan and other documents,combined with the situation of field research,the analysis believes that the construction environment around the square subway station is complicated.Mainly manifested in the following aspects:large traffic flow in the construction area,dense buildings(structures),a large number of pipelines underneath,abundant groundwater,and adjacent cultural relic protection buildings.There are many primary risk sources,in view of the above factors,it is necessary to conduct risk analysis before construction of the project.Combining the characteristics of the square subway station’s own engineering and the surrounding special environmental background,identify the main potential risk sources and hidden dangers of the square square subway station,carry out engineering risk analysis on the identified own risks and environmental risks,it is considered that the excavation range and depth of the half-covered section of the square square subway station project is relatively large,it is a dangerous project of a certain scale,during the unloading process of the soil in the foundation pit,attention should be paid to the settlement impact on the adjacent cultural relics protection buildings,therefore,the two first-level risks of the semi-excavated section of the foundation pit excavation and the adjacent cultural relics protection building in the project are regarded as the research focus.on the basis of,combining qualitative and quantitative methods to conduct risk assessment of square-shaped square subway station,build a risk assessment model,use the sum-product method to calculate the weight of each risk factor,analyze and evaluate the construction risk according to the weight value of each influencing factor,it is obtained that reasonable improvement of the construction plan of the half-cover excavation section of the foundation pit can reduce the disturbance impact on the cultural relics protection building,conducive to control the settlement impact generated during the excavation of the foundation pit,it has the greatest impact on the construction risk control of the entire project,lay the foundation for the subsequent use of numerical simulation methodsto improve the construction plan,at the same time,establish a risk monitoring and control system during the construction phase,and put forward engineering monitoring suggestions.Based on the results of construction risk analysis,identification and assessment,consider the complexity of the construction environment,it is established that the focus of the improvement of the construction plan is the construction of the half-cover excavation section,therefore,it is further combined with three-dimensional software numerical simulation analysis,calculate the influence of excavation on the surrounding ground settlement,the horizontal lateral offset of the ground connecting wall,and the stress of the enclosure structure.The study found that the allowable settlement value of the cultural relics protection building after construction according to the original plan is greater than the code requirement,need to be improved accordingly.Therefore,a construction plan for the permanent roof support structure of the half-side station is proposed.Compared with the original plan,it is found that the improved permanent roof support system construction plan has obvious advantages,can increase the overall structural rigidity,greatly reduce the impact of foundation pit excavation on the surface settlement outside the pit,effectively control the lateral stress of the soil outside the pit on the supporting system after unloading the soil inside the pit,reduce the horizontal lateral deviation of the underground continuous wall system,reduce the impact of excavation on the stress and deformation of the enclosure structure,verified that the improvement plan is feasible and effective,it can provide reference for later station construction,it also has certain reference significance for the construction of other urban subway stations in similar situations.