The Upper Reaches Of The Yangtze River Rocky Water Construction Key Technical Difficulties And Safeguards Research

Location of the project, mainly shallow hill terrain, is higher in the east and north and lower in the west and south. Bedrock exposes from the hills. The rock layer exposed is Shaximiao mudstone of the Jurassic mid-stream and interbedded sandstone of the feldspar quartz. Clayey soil exists in the hallow areas. There is mudstone and sandstone in the riverbank of water supplier. Rock layer in the water supply plant area is basically stable and there are no obvious landslides, collapse or other adverse geological phenomena in the area.The upper reaches of the Yangtze River has a mutated terrain with high mountains and deep valleys. Some part of the river bank has a wide valley and most of the river bank is narrow for the river to flow through. Besides, slope of the river is quite precipitous and current in the river flows fast. Taken those into consideration and combining the topography features in the project area, blasting construction was chosen for the construction of diversion tunnel and pumping station in this project.Total length of diversion tunnel is333m.180m of the pipe were buried under the river bed and were constructed by means of open channel excavation. The rest153m were buried in the tunnel. Inner diameter of the pumping house is22m and depth is47m into the rock foundation. The foundation is mainly IV and V Class Rock and is quite sturdy and difficult for the construction.During the construction, blasting monitoring was carried out in the form of on-site precision level measurement to ensure safety and quality of the construction. Monitoring items mainly included surface subsidence measurements of the shallow cave segment at ends, crown settlement, horizontal convergence, state observation of the surrounding rock and support.During the whole construction process, the maximum settlement value of the Tunnel vault is0.41mm, the maximum surrounding convergence is0.39mm and the maximum settlement value of the surface is0.23mm. Vault sedimentation rate, convergence rate and surface subsidence rate are all below0.1mm/d. the tunnel basically stays stable and there is no casualty in the whole process.Analysis and calculation of the tunnel monitoring data shows that:Unnel vault settlement, surrounding convergence and surface settlement all meet the requirements of relevant design regulations;During the monitoring process, monitoring task in terms of the tunnel monitoring was fulfilled in strict accordance with the project monitoring program regulations. Feedback data was provided in time and tracking service was also offered. Monitoring items meet all the technical requirements and regulations from the construction units, supervision departments and owners and thus provided effective and reliable data for the tunnel construction and surrounding building and ensure safe construction of the tunnel.