Experimental Study On Factors Affecting Coal Breaking Load Of Two-wing Dry Coal Drill

Drilling stress method is one of the most typical methods for predicting impact ground pressure,the method predicts the risk of impact rock burst by detecting the change law of the stress magnitude of the coal stress during punching,the coal body stress can be obtained indirectly by measuring the bit load,but the factors affecting the bit load change are very complicated.In addition to the coal body stress,there are many factors that will affect the bit load change.Therefore,the factors affecting the bit breaking load of the bit can be Accurately obtain the foundation of the coal body stress.In order to analyze the factors affecting the change of drill load under complex working conditions,this paper uses the combination of theoretical derivation,experimental exploration and field verification to study the relationship between coal body stress,coal rock mechanical properties and drilling parameters and drill load.Through theoretical analysis and experimental tests,some of the results of this study can be drawn as follows:Firstly,through the force analysis of the drill bit,the mechanical model between the bit torque and thrust and the coal body stress,coal rock hardness,coal body strength,coal brittleness,cohesion and internal friction angle is established,and based on the contact relationship between the drill bit and the drill pipe and the coal rock,the dynamic model of the drill bit drilling process is established.Secondly,using the similarity theory to develop the drilling test bench,the different coal body stress,coal rock hardness and propulsion speed are tested and tested.The relationship between these three factors and the bit torque and thrust is studied.The research results show that,both the bit torque and the thrust increase with the increase of the coal body stress,so the bit load is positively correlated with the coal body stress;The bit torque and thrust are positively correlated with the hardness of coal rock.The bit load and the hardness of coal rock increase linearly in a certain hardness range.The bit torque and thrust are positively correlated with the hardness of coal rock.The bit load and the hardness of coal rock increase linearly in a certain hardness range.Finally,field tests were carried out on three working faces with different buried depths to verify and explore the relationship between the factors such as coal stress,propulsive speed,mining stress,brittleness of coal and rock,and the bit torque and thrust,and preliminarily determines the stress relaxation zone,stress concentration zone and original stress zone of the selected working face.This thesis has 69 figures,10 tables and 68 references.