Study On Construction Technology Of Long-distance Diversion Tunnel With Small Cross Section

In Tianshui City,the Yin Tao water supply project is a major project in Gansu Province,and the Tianshui City’s largest investment in the history of water projects,and also the main water supply project in the future of Tianshui City which concerns the 80 million people’s water drinking issues.After the completion of the project,it will improve the current water shortage in Tianshui City,and provide effective water resources to the fast development of the city.The water is diversed from the end of the four main drainage channels to Tianshui City.No.2 tunnel is located in the middle of the water diversion pipeline,and the hole axis go through the mountains between Gangu County and Qinzhou District.Area of tectonic Qinling tectonic belt,he Qi Lv "mountain" type construction system and Longxi of vortex structure of complex area,geological structure complicated background history of frequent seismic activity in the region,belonged to regional tectonic stability of tunnel projects in those areas.Since the project started,excavation and tunneling in the various complex geological conditions,frequently crossing the fault,fault zone,groundwater rich in individual sections of the gushing water,sand and other phenomena,caused great difficulties to the excavation.No.2 diversion tunnel excavation section has an area of bout 8.2m2,belonging to small section,with the main hole length of 8.72 km.The "small cross-section long distance" features,coupled with poor engineering geological conditions,result in frequent landslide during construction.The work face is narrow,thus large construction machinery can not be used.There are a variety of problems such as processes interfere with each other,the process of convergence with the difficulty,and the low efficiency.This paper takes the water diversion tunnel No.2 of Tianshui City as the research object,through the technical and economic analysis and the comparison of the specificity of the engineering basic situation,the regional engineering geological condition,the construction process,the construction cost and the working efficiency,we proposed a various types of construction projects,as well as special construction programs to deal with a variety of complex geological conditions and special sections.This paper has carried on the detailed design to the excavation of the main hole of the samll section and long distance hydraulic tunnel and the construction scheme of the primary support,the secondary lining construction scheme,the construction branch hole support scheme and the construction auxiliary facility plan,focusing on the description of the blast drilling and digging excavation treatment,the landslide treatment of the cross section of the main hole and the branch hole.The application of the key construction technology in the project is described in detail.This paper has carried on the deep thought to the construction management of the small section long distance hydraulic tunnel,has sorted out some construction problems which frequently appeared in the construction of such tunnel,summed up the methods of coping with and solving such problems,and accumulated the experience of construction management,providing reference to similar type of hydraulic tunnel construction,which has a certain universal significance.