The Rock Fracture Mechanism During Conical Pick Indentation Based On Discrete Element Method

The cutting gear is a part of mining equipment such as shearer which directly acts on coal rock.Its cutting performance and load characteristics directly affect the cutting efficiency of mining equipment.At the same time,with the continuous increase of coal mining depth,deep complex coal seam geological conditions further improve the difficulty of cutting rock.Therefore,an in-depth analysis of the mechanism of the cutting teeth intruding into broken coal rock,especially in heterogeneous coal rock and complex environment,can provide a theoretical basis for the design of cutting machines and tools,and has important significance for the design and improvement of deep coal seam mining equipment.In this paper,coal and roof and floor rocks(red sandstone)are selected as the research object,and the rock model and the truncated intrusion rock breaking model are established by using discrete element software PFC2 D.The effectiveness and reliability of the discrete element model of truncated intrusion rock breaking are verified by comparing with the rock breaking test results under different cut thickens.Based on the discrete element model of intercept intrusion,the influence of intercept intrusion Angle and intrusion spacing on the process of coal and rock intrusion is studied.The results show that the wedge intrusion Angle mainly affects the crushing zone and the direction of crack growth.The crush zone expands with the increase of the invasion Angle,and the larger invasion Angle is conducive to the horizontal propagation of the main crack at the tooth tip,so as to improve the granularity of rock breaking debris and reduce the specific energy consumption of invasion.This phenomenon is more significant for the red sandstone with high brittleness.Both the lateral force and the intrusion force increase with the increase of the intrusion Angle,while the specific energy consumption and specific crack quantity increase first and then decrease.The simulation analysis of the intrusion spacing shows that the optimal intrusion spacing of the picks is affected by the characteristics of coal and rock,and the red sandstone with greater brittleness has smaller intrusion and fracture affected area,so the optimal intrusion spacing is smaller.The coal rock intrusion model with structural plane is constructed,and the influence of structural plane dip Angle,spacing and shear strength on the intrusive crushing process of coal and red sandstone is simulated.It is found that the Angle of structural plane mainly affects the direction of main crack propagation under the condition of low shear strength of structural plane.The first macroscopic shear crack along the structural plane is formed outside the crushing zone.With the increase of the Angle of the structural plane,the macroscopic crack tends to extend to the coal rock,and the lateral and intrusive forces of the truncated teeth in the intrusive coal and red sandstone decrease,and the specific energy consumption and specific cracks increase.The spacing of structural plane mainly affects the fracture morphology of coal and rock,but has little effect on the invasion load of cutting teeth.As the distance between structural planes increases,the weakening effect of coal and rock strength decreases.The analysis of the shear strength of the structural plane shows that when the shear strength of the structural plane is lower than that of the coal rock,it has a limiting effect on the crack propagation during the invasion process.Finally,the model of coal and rock intrusion breakage under confining pressure is constructed,and the simulation analysis of coal and red sandstone intrusion breakage under confining pressure is carried out.The obstruction and influence mechanism of confining pressure on the macro-crack in the process of the two kinds of coal and rock breakage with different brittleness are the same.Under confining pressure loading,the horizontal stress in coal is increased,which is conducive to horizontal crack propagation and hinders longitudinal crack propagation.However,as the confining pressure continues to increase,it shows the effect of strengthening coal and rock,restricting the expansion of all macroscopic cracks,and the brittle failure form changes to plastic failure.The interception force increases with the increase of confining pressure,and the influence is more significant for the coal rock with low brittleness.With the increase of confining pressure,the specific energy consumption and specific crack amount of intrusive coal increase and tend to be stable,but the influence on the specific energy consumption and specific crack amount of intrusive coal is small.There are 87 figures,5 tables and 107 references in this dissertation.