The Study On Risk Management Of Underwater Shield Tunnel

With the development of society,urban traffic congestion is becoming increasingly serious in recent years.Practice has proved that urban rail transit construction is one of the most effective ways to solve the urban traffic congestion.However,in recent years,the engineering accidents happened in urban rail transit construction frequently,resulting in a large number of casualties and property damage.Hydro-geological conditions of Underwater tunnel are complex,such as many uncertain factors,complexly shielding construction process,difficulty mechanical control,the risk is much more serious.The lack of effective engineering risk management measures is one of the main factors.In order to ensure the smooth and safe construction of underwater tunnel construction,it is necessary to study the risk management of underwater tunnel shield construction.Lanzhou subway is the first urban rail transit project line built in the Loess Plateau area.Compared with other urban rail transit projects,due to the special hydro-geological conditions and the surrounding building environment,the cutter tool is damaged during the tunneling process,Ground subsidence,shield mud surge,underground pipeline damage,ground building damage and many other technical risks.Coupled with the YingMenTan~MaTan area shield tunnel through the Yellow River,the construction safety and progress are seriously affected.In order to ensure the safety of the construction work smoothly,this paper takes the Lanzhou Rail Transit Line 1 as the object of study,and establishes the risk assessment index system by combining the qualitative and quantitative methods.(1)On the basis of expert consultation,six major indexes,such as mechanical risk,manual operation risk,hydrogeological risk,construction environmental risk,natural factors,humanities and social environment,were established,and Lanzhou subway was built with shield tunnel construction Risk index system.(2)The use of analytic hierarchy process to assess the possibility of risk factors,fuzzy evaluation and matrix analysis of the risk state to estimate.The results of the first-level index show that the risk of construction machinery,the risk of man-made operation and the hydrogeological risk level of Lanzhou subway shield are "serious".The second-level index evaluation results show that the large-scale pebble boulder and saturated sand Are 4,is the tunnel tunnel construction of a major source of risk.(3)During the construction of the shield tunnel of the Yellow River tunnel through the Yellow River tunnel,there are accidents such as the damage of the cutterhead caused by the large particle size pebble boulder layer and the saturated sand layer and the collapse of the project.Which is consistent with the conclusion of the risk assessment in this paper,and puts forward the technical measures to deal with the risk of abrasion of sand and gravel layer in the shield tunnel construction of Lanzhou subway.