Study On Construction Risk Assessment And Prevention And Control Measures Of Underground Caves In Complex Environments

With the continuous improvement of people ’s material life,the number of vehicles has increased rapidly,making urban traffic overwhelmed.The rapid development of urban traffic has led to less and less ground traffic space.Opening up underground space has become a new direction of urban traffic construction.Due to the complexity of urban environment,there are many risk factors in the construction process of underground caverns,which have a serious impact on the construction safety.Therefore,in order to reduce the risk in the construction process of underground cavern group and better guide the engineering practice,this paper relies on the third phase of underground cavern group project of an underground ring road in Chongqing,and studies the construction risk assessment and prevention and control measures of underground cavern group in complex environment.The main research results are as follows:(1)Combined with the complexity of urban underground caverns environment and construction characteristics,the construction risk assessment model of urban underground caverns based on fuzzy hierarchy comprehensive evaluation method is established.(2)The construction risk assessment model of urban underground cavern group is used to identify the risk of underground cavern group in the third phase of an underground ring road in Chongqing,and the construction risk assessment index system of underground cavern group is established.At the same time,the construction safety risk assessment was carried out,and the construction safety risk level of each section was obtained.(3)Through the finite element numerical analysis,the construction safety prevention and control measures of different excavation methods,excavation sequence and excavation footage are studied for the overlapping section with high risk level.Combined with safety and economy,the research results show that it is suggested that the main channel tunnel should adopt the CD method,the power tunnel should adopt the full section method,and the left and right line tunnels of Jiabin Road should adopt the excavation method of annular excavation and reserved core soil method.It is recommended to excavate the Jiabin Road connecting tunnel first,then excavate the power tunnel,and finally excavate the excavation sequence of the main channel tunnel.It is suggested that the excavation footage of the main channel tunnel is 2 m,the excavation footage of the power tunnel is 3 m,and the excavation footage of the left and right lines of Jiabin Road is 3 m.(4)The monitoring measurement values and numerical simulation analysis results of the construction site of the underground cavern group are compared and analyzed.The numerical simulation values and the measured values meet the relative displacement control standard and the displacement change rate control standard.The deformation process is basically the same,and the curve graph trend is similar,and the effectiveness of the prevention and control measures taken is verified.