Simulation Research For Clamping System Of Full Rotary Casing Drill Rig

Full-rotary drill rig is a new equipment on the basis of the Casing Oscillator, mainly for pulling and replacing urban underground obstacles, hard-rock drilling on cities and coastal area, construction on complex broken formation, while in the rotary drilling and using the casing to protect the hole wall, the equipment using the drilling tools such as the grab, impact hammer to clear or in-situ crushing the rocks and obstacles in the casing.The casing body and the clamping system is the most important part of the full casing equipment. The main work of the casing is not only a drill pipe but also protecting the wall of the drill hole, which is bearing complex stress, while the clamping mechanism in the clamping of the casing can pass axial force and rotary torque at the same time, both of them directly affect the safety and reliability of the drilling.This paper combines the basic theory research and calculation mechanics, involving the elastic-plastic mechanics, the drill string mechanics and nonlinear finite element analysis, etc. The tensile strength-orque model of the casing and the nonlinear finite element calculation model of slip is established, using the load incremental method, penalty function method and Newmark method to calculate the stress state of the slip in the case of multiple nonlinear coupling of stress.Main work and conclusions are as follows:(1) summarized the overseas and domestic research status of the construction method of the full casing drilling, combining with the field application situation in our country, sums up the construction technology including bored piles,secant piles and deep obstacle cleaning of the whole casing drilling.(2) established the mechanical model of the casing of casing drill, and analysis the casing in the condition of axial tension and compression stress, discussed its principal stress status and change situation with the Mohr-circle theory.(3) analysis the whole statics on the casing, and summarizes the general rule of casing on the stress distribution:in the drilling process, the composite stress is small in the middle of casing string, and increased gradually from the middle to both ends,after applying the torque,the force curve changed gentle,and in the pulling process,the composite stress changed linearly from top to bottom,the maximum at the top and minimum at the bottom.(4) finished the research of the finite element mechanics theory of the slip, including the elastoplastic theory, nonlinear theory and the transient dynamics theories,etc.(5) software is used to the nonlinear finite element analysis of slip, which laid a foundation for optimum design of slip, analysed the changing rule of the calculation results when some parameters changed such as the design style, the radian, height and thickness of slip.The result shows:compared with the lining strips slip,the stress distribution of the glossy structure slip is more uniform,and when the radians between35°～40°,the height is about650mm and the thickness of the slip is about30mm,the stress distribution of the slip surface is more uniform.