Study On Construction Safety Risk Control Of Connecting Passage Of Metro Tunnel In Rich Water Sand Layer

With the sustained and rapid economic development and the increased urbanization,the construction scale of subway projects is constantly expanding.In the process of subway construction,in order to meet the functional needs,such as passenger evacuation,tunnel drainage,fire prevention,and disaster prevention,the cross passage should be established between the two subway tunnels.There are hidden safety hazards in the construction of the connected aisle.Firstly,it involves engineering risks such as water gushing,sand collapse,impact on existing tunnels,and damage to pipelines in the construction area.Secondly,there are non-engineering risks such as electric shock,equipment failure and object strike.In the actual construction of the connected aisle project,safety accidents occur from time to time.Especially in soft soil layers such as water-rich sand layers.There are many major risk accidents such as the ground to collapse caused by sudden water gushing and sand gushing due to the poor stability of the soil layer itself.Therefore,it is necessary to carry out research on the safety risk management of the connected aisle construction under the conditions of water-rich sandy soil layer.First of all,by consulting the research status at home and abroad,this article starts with the construction method of the subway connected aisle.Analyzed and compared the three types of excavation methods of open-cut method,hidden digging,first open digging and then deep digging,as well as three types of auxiliary construction methods of ground reinforcement,grouting reinforcement in the tunnel and freezing method.Then,come by with the characteristics of the water-rich sandy soil layer,the frozen excavation is more suitable for the construction of the connection channel of the water-rich sandy layer.Secondly,by conducting risk identification and evaluation of the whole process of the frozen excavation of the cross passage in the water-rich sandy soil environment,the main risks and general risks in the construction process are determined,and the corresponding risk control measures are formulated.At the same time,the ABAQUS finite element numerical simulation software is used to simulate and analyze the reasonable time of active freezing and the displacement caused by freezing.Based on this,reasonable active freezing time and tunnel reinforcement measures are determined.Finally,an empirical analysis has been studied,which based on the subway connection channel of a water-rich sand layer of Metro Line 5 in a city.According to the main safety risk control measures for the construction of the frozen excavation of the water-rich sand layer subway connected aisle,targeted engineering risks control measures are proposed combined with the actual situation.After using the ABAQUS finite element software to simulate the development of the freezing curtain and the frost heave displacement of the soil during the active freezing period,it is proposed that the active freezing period of this project should be in 45 to 55 days,and specific guidance suggestions for the use of conventional reinforcement measures in the tunnel.The feasibility of using freezing method and main safety risk control measures for the water-rich sand layer subway connection channel has been confirmed through the actual construction effect.And the result could provide a reference for the research on safety risk control measures of similar projects.