Study Of Safety Risks And Control Measures Of Hefei Metro Construction

The construction conditions of urban rail transit project are complex and affected by many factors,which leads to frequent accidents.Based on the investigation and study of engineering geology and hydrogeology characteristics in Hefei area,this paper studies the risk factors and characteristics of Metro construction.Based on the construction risk analysis of typical stations and tunnel projects,the corresponding construction safety control technologies and measures are put forward.The main contents and achievements of this paper are as follows:(1)The engineering geological characteristics of Hefei and the adaptability of metro construction methods were studied.Based on the analysis of engineering geology and hydrogeology characteristics of Hefei,the geotechnical distribution and mechanical parameters of soils along the metro line are obtained,and the expansive characteristics and laws of typical expansive rock and soil are revealed.The influences of formation conditions of Hefei on metro construction methods and construction control measures are analyzed.(2)The safety risk characteristics of Hefei metro construction are analyzed and risk assessment methods are studied.Combined with the construction environment of Hefei metro,the main risk sources of Hefei metro are analyzed.The study shows that the main geological risk factors of Hefei metro construction are expansive soil layer,water-rich soft soil layer,upper soft and lower hard stratum,Nanfeihe River and so on.In addition,there are a large number of construction and underground pipelines along Hefei Metro line,which are important risk factors.(3)An improved fuzzy comprehensive safety risk assessment method is proposed and applied to the construction risk assessment of Wangjiang Road Station of Hefei Metro Line 3,which lays a foundation for the construction risk assessment of Hefei Rail Transit.(4)Construction risk and control technology of deep foundation pit in subway station under complex environment are studied.Taking Taihu Road Station of Hefei Metro Line 1 as the background,the risk sources in the construction process are analyzed,and the influence of deep foundation pit excavation on ground settlement around foundation pit,horizontal deformation of retaining piles and pile foundation deformation near viaduct is analyzed by numerical simulation method.Risk control measures and techniques are put forward.The technical methods include the protection of the deformation and destruction of the foundation pit itself,and the protection of the surrounding buildings and underground pipelines.(5)Construction risk and construction safety control technology of typical subway stations with water rich formations are studied.Combined with Dadongmen Metro Station,the construction risk of deep and large foundation pits in typical water-rich strata in Hefei is analyzed,and corresponding safety control countermeasures are put forward from two aspects of design and construction.Dadongmen Station has the characteristics of high groundwater level and pressure bearing,poor stratum condition,deep foundation pit,complex station structure and adjacent buildings.The main risk sources are foundation pit instability,deformation and damage of surrounding buildings and pipelines,leakage of maintenance structure and construction quality of main structure.The corresponding measures for design and construction are put forward:retaining foundation pit with underground diaphragm wall,reverse construction with cover and excavation for main structure,strengthening waterproof design and waterproof and drainage measures in construction,local soil reinforcement and protection of surrounding buildings.(6)The risk and control measures of the adjacent construction of metro shield tunnel are studied.This paper analysed the construction safety risks of shield tunneling under line 1 of Hefei Metro through Nanyihuan Municipal Tunnel,and puts forward the measures of pre-reinforcement with rotary jet grouting piles for the floor of existing municipal tunnels and enclosure with glass fiber piles for the structure of municipal tunnels,which provide conditions for shield tunneling and cutting enclosure piles;and advances construction parameters such as construction speed during shield tunneling.The shield construction process is analyzed by numerical simulation,which shows that the deformation of municipal tunnel is within a reasonable range.Risk analysis of long-distance side-crossing bridge pile foundation construction of metro shield tunnel is carried out.Different reinforcement measures of bridge pile are proposed according to different proximity.Construction parameters such as construction speed are optimized to ensure the safety of bridge pile foundation.