| As the low-carbon economy and environmental protection have become the themes of today’s world development,my country’s energy consumption structure has also been optimized and adjusted accordingly.As an efficient and clean energy,natural gas is an inevitable choice for China to develop a low-carbon economy and achieve environmental protection in recent decades.The application of pipelines to transport natural gas can fully realize the development concept of diversified gas sources in my country.The Yongqing-Shanghai section of the Sino-Russian East Route Natural Gas Pipeline Project is mainly responsible for transporting Russian natural gas resources to important gas markets such as the Bohai Rim and the Yangtze River Delta to ensure the safety of gas supply in the economically developed regions of the Bohai Rim and the Yangtze River Delta.The pipeline traverses the Yangtze River in the form of a shield tunnel in Jiangsu Province.The horizontal length of the shield is 10.226 km,which is the longest shield tunnel at home and abroad.The pipeline traverses the Yangtze River levee,the anchorage of the Changshu marine vessel,the main channel of the Yangtze River,the core area of the Yangtze River saury aquatic resources protection,and the Baimaokou Wetland Reserve.It faces multiple difficulties such as crossing high water pressure,soft soil containing biogas,and ultra-long distance shields.Therefore,it is of great research significance to find out the engineering geological conditions,hydrogeological conditions and the characteristics of the soft soil layer containing biogas in the crossing area,and to carry out economic,reasonable and safe shield design.This article first introduces the general situation of the Yangtze River shield project,the hydrological characteristics of the crossing area,and the regional geology.Through technical means such as drilling,rock and soil tests,shallow water seismic,side scan sonar,and hazardous gas surveys,the project has been identified.Geological conditions and main problems.According to the survey results,the pipeline is suitable for crossing the river by means of shield tunnels.The main influencing factors are: the highest water pressure of the tunnel in the water area is 0.73 MPa,the water influx is large,the erosion is severe(the lowest point of erosion is-39.5m),and the soft soil layer containing biogas is irregularly distributed.On the basis of extensive collection of similar engineering design data and comprehensive analysis and survey results,the overall crossing plan,shaft and leveling design are carried out.The main results obtained are as follows: the shield tunnel adopts single-layer lining,C60 reinforced concrete flat segments,and has an impermeability grade of P12.It has greater bending rigidity and good compression and impermeability,and it has solved high water pressure and The problem: The depth of the shafts on both banks has been increased,the curvature of the tunnel has been optimized,and the thinnest part of the overlying soil thickness under the comprehensive envelope of scouring has been 26.3m,which solved the problem of severe erosion of the Yangtze River in the crossing area;The thickness is 1200 mm,and a circle of sealing 800 mm thick plastic concrete wall water-stop curtains is set,and a total of 56 dewatering wells are arranged,which solves the problem of large water influx.At the same time,the exhaust pipe is arranged to empty the biogas in advance,strengthen ventilation,and monitor.Technical measures to ensure the safety of the construction of soft soil containing biogas. |
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