Research On Security Risk Assessment During Construction Of Xishan Tunnel

The length of Xishan tunnel is nearly 28 km,belongs extra-long tunnels.The complex geological conditions and lots of poor geology cause great difficulties for the design and construction of the tunnel.The design,technology and experience requirements on construction are higher.Tunnel engineering has a larger scale,and once appeared the security risk accident,there will cause great economic losses and an extremely bad social impact.Then it must be part of the risk assessment in the tunnel engineering.This paper has carried out the following tasks:(1)Surveying and counting the major risk events and their main risk sources of Xishan tunnel by using the expert investigation method,assessing the level of risk associated Xishan tunnel risk events.Determining the risk events of level ? for three,namely water inrush and mud burst,construction duration designing and tunnel collapse;the risk events of level ? for six,namely gas explosion,the hole instability,large deformation,ventilation and disaster prevention,rock burst and environmental protection;the risk event of level ? for longitudinal drainage.(2)Reading,understanding and analyzing geological exploration data,preliminary design and construction drawing design data of the main hole in Xishan tunnel,and identifying,assessing and controlling the major risk events and their main risk sources of the tunnel on the basis of risk analysis.Then,when analyzing the tunnel segment,the probability of each risk level events in each segment will be targeted analyzed.At the same time,ranking the importance of risk source by using analytic hierarchy process(AHP),combined with expert survey on identifying the risk source of risk events in the tunnel,suggesting that targeted measures should be adopted to control the related risk events in accordance with the importance of risk source sorting,and reducing the risk level of the risk events.(3)On the basis of risk assessment,this paper puts forward the targeted control measures,combined with the original preliminary design and construction design risk control measures,especially for level ? risk events and gas explosion risk.(4)Due to the large dimension of the inclined shaft and vertical shaft of Xishan tunnel,this paper takes a special risk assessment for the inclined shaft and vertical shaft of Xishan tunnel,identifies and assesses the major risk events for the inclined shaft and vertical shaft design stage on the basis of risk analysis.And then the control measures are suggested.