Analyze On Deformation Characteristics Of Horizontal Directional Drilling Through Main Canal Of Middle Route Of South-to-north Water Transfer Project

The main canal of the middle route of the South-to-North Water Diversion Project spans a number of provinces and cities,with a total length of 1432 km.Since the project was put into operation on December 12,2014,with the economic development of cities along the route,more and more projects need to be built,and crossing projects in the middle line of the South-to-North Water Diversion Project will be inevitable.Among them,the horizontal directional drilling crossing project is in the majority.Because the construction technology of horizontal directional drilling crossing project is still not perfect,such as track line control,mud pressure control and so on are prone to deviation,and then produce phenomena such as surface deformation,irregular holes and so on,which may cause safety impact to the main canal project of the middle route of south-to-north water transfer project.Therefore,this paper studies the deformation characteristics of horizontal directional drilling through the main channel of the middle route of the South-to-North Water Transfer Project.Analyze the influence of crossing on the deformation of main channel under different conditions and the deformation law.The choice of suitable burial depth and reasonable mud pressure under the same canal section along the line is discussed.In this paper,the typical failure modes and the influencing factors of directional horizontal drilling are summarized.An example of a typical directional drilling project in Yongnian County crossing the main channel of the middle route of the South-to-North Water Diversion Project is analyzed.The numerical simulation model is established in the finite difference software FLAC^3D,and the rationality of the model is verified by the measured data.On this basis,the research on the key control parameters of buried depth,mud pressure and irregular hole was carried out.Based on numerical simulation,theoretical calculation and practical construction,the reasonable control range of key parameters for horizontal directional drilling across the main canal of the middle route of the south-to-north water transfer project is obtainedAccording to the theoretical calculation results of irregular gourd hole height formed by the sinking of reamer,the maximum hole height of irregular hole is generally 1.5～2.5 times of the design value.According to Numerical simulation results show that the maximum and minimum principal stress difference at the top of irregular calabash hole is about 1.5～1.8times of that of circular hole under different working conditions,and shear failure at the top of irregular calabash hole is more likely to occur than that of circular hole.Under the same working condition,the irregular calabash cavity has a greater influence on the settlement of the ground and the main channel than the circular cavity.Combined with the theoretical calculation,numerical simulation and actual construction conditions of mud pressure,the deformation characteristics and influence analysis of crossing under different working conditions were carried out by taking the buried depth,mud pressure and irregular hole as the key control parameters,and the displacement and stress variation rules under different working conditions were obtained.The numerical results show that when horizontal directional drilling penetrates along the main canal of the middle route of South-North Water Diversion Project,the suitable burial depth in the project should not be less than 15D below the canal bottom,and should not be less than 15m.The theoretical calculation and numerical simulation results show that the theoretical calculation range is0.9～1.3yh,which is a reasonable range of mud pressure in the project.