Study On Double-pipe Crossing Technology For Large Excavation Of Sand And Gravel Geological River

As for large rivers with sandy cobble geology,due to the depth of the river scour line,the deep excavation of the pipe trench,the soft soil and collapse,the difficult trench forming,the high permeability coefficient of the river bed and the large seepage volume,it is a great difficulty for the river to dig through the construction.With the rapid development of the national economy,the efficient,fast and environmentally friendly method-steel sheet pile has been widely applied in many major construction projects,and steel sheet pile cofferdam is an important field of application.The domestic section of the Sino Burma oil and gas pipeline project is crossed by the Ruili River.In the domestic oil and gas pipeline construction,it is the first time to adopt large excavated double pipes to cross the large sand gravel geological river.Combined with the design and construction of Ruili River crossing,the crossing ways and key technology of large sand gravel geological river excavation and double tube crossing are studied.The main contents of this paper are as follows:On the basis of thorough investigation at home and abroad on the crossing mode of large excavated pipes,the research on crossing technology of sand gravel geological river determines the crossing position,comprehensively analyzes its natural geographical conditions,engineering geological conditions,hydrogeological conditions and various factors of earthquake according to the selection principle of crossing position.According to the unfavorable geological conditions of Ruili River,synthesizes Ruili River double crossing engineering overall alignment,natural and geographical conditions,geological and hydrological conditions and so on,through feasibility analysis of crossing methods,get a reasonable crossing one,economically compares the selected crossing methods,and finally determines the double pipe crossing scheme which needs further studying.According to the relevant data of Ruili River,the crossing scheme design,check and aseismic design are carried out,so as to complete the preliminary design of crossing engineering,it also guides and refers to key technologies such as crossing construction.Through analyzing the characteristics and difficulties of crossing construction,according to the actual situation of the site,the construction technology plan is worked out,and the construction method of "steel sheet pile half cofferdam + buoy pump strong row" is adopted.Combined with the survey and excavation soil permeability test,make construction plan,according to the construction procedure,the technical requirements for double pipe crossing construction are described in detail,especially for construction preparation and measurement,drainage,excavation of pipe trench,installation group welding,pressure test and stabilizing pipe.Combined with the situation of the crossing position of the Ruili River,the relevant risk mitigation measures are designed from the risk-based perspective to ensure the safety of the pipeline operation.Through the Ruili River crossing project,the crossing technology of sand gravel geological River has been studied,and the research achievement can reach the reliable implementation requirements of the sand gravel geological river crossing,and provide a reference for similar stratum crossing construction in the future.