Research On Coal Stress Inversion Based Of Bit Drilling Parameters

Mine downhole disasters have always been the key factor restricting the safe production of coal mine.In recent years,the frequent occurrence of mine safety accidents has had a great impact on the production.For the prevention and control of mine downhole disasters,coal seam drilling technology has been widely used for its convenience in construction and good pressure relief effect.In the process of disaster management,the measurement and analysis of coal stress has always been the difficulty of technical breakthrough,and the current measurement of coal stress is also limited and not timely,resulting in sometimes not timely disaster control.Therefore,this paper adopts the methods of theoretical analysis,numerical simulation and field application comparison to analyze drill bit drilling,and then proposes a method to use drilling parameters to invert coal stress based on energy conservation.In this paper,the mechanism of drilling and rock breaking,the influencing factors of rock breaking cutting force and the response law of drilling parameters are studied deeply.The main research contents and achievements are as follows:(1)through Mohr-coulomb failure criteria of rock mechanics,the drilling rock bit of simplified stress analysis,cutting and drilling down into pressure into two basic movements,the depth of invasion was deduced and the calculating formula of cutting force under different conditions,when the drill blade pressure into the coal,pressure depth and the axial thrust of coal,coal stress of extrusion,cohesive force,internal friction Angle of coal,diamond blade Angle,diamond blade width;When the drill edge cuts coal,the cutting force is related to the penetration depth,the coal stress,the coal cohesion,the coal internal friction Angle,the drill edge Angle and the width of the drill edge.(2)in this chapter,through theoretical analysis and numerical simulation,the main influencing factors and influencing laws of cutting force in the cutting process are analyzed,and the PFC-2d discrete element model of cutting is established on the basis of theoretical calculation results for cutting verification,and the linear positive correlation between cutting force and coal stress is obtained.The half Angle of the cutting edge has a certain influence on the cutting force.There is a certain relationship between the total number of cracks and the stress of coal body when the main crack appears,and the number of cracks increases slowly.(3)based on the law of conservation of energy,the drilling parameters associated with the stress of coal,and the drilling with the Abaqus simulation verification,put forward a method of using drilling parameters inversion coal stress,and theoretical analysis,the parameters of drilling and the loss is analyzed to verify the result with field drilling,confirmed the feasibility of research,a method for stress analysis of coal is put forward.