| The roadheader is currently the key equipment used in the mechanized construction of coal mine roadway.However,for the hard rock roadway,the existing roadheader cannot achieve economical cutting,which seriously restricts the coordinated development of coal mine production.In order to improve the efficiency of hard rock roadway excavation and promote safe green mining and clean and efficient use of roadway,the coal industry can achieve green and economic sustainable development.Based on this,this paper proposes a joint rock-breaking method using hydraulic fracturing and cutting heads.Using a combination of theoretical,numerical and experimental methods,systematically studies the parameters such as strength of rock mass,confining pressure,number of pores,etc.The weakening law of the rock mass in the rock breaking and the effect of the rock breaking performance of the cutting head revealed the hydraulic crack propagation mechanism of the rock mass and the rock breaking mechanism of the rock containing the pores and cracks.It provides important reference for theoretical design and practical value of designing the parameter design of hard rock for hydrofracturing weakening.Based on the theory of fracture mechanics and the theory of cohesive crack propagation,the displacement model and the crack initiation and propagation mechanism in the cohesive crack propagation problem are analyzed.The hydraulic fracturing process of rock samples is simulated by ABAQUS software and the hydraulic fracturing is analyzed.Crack propagation mechanism and failure mode.Based on the theory of cutting rock breaking,using the AUTODYN software to simulate the rock cutting process under a single pick,the broken mechanism of the rock sample under the pick was analyzed.Based on the similarity ratio theory of materials,four rock samples with different hardnesses were configured and the mechanical parameters of the configured rock samples were measured.The effect of different mechanical properties,number of pores,and mode of crack propagation on the water pressure and crack propagation of hydraulic fracturing in rock mass was studied by using a drilling rig and a hydraulic fracture test rig.Research shows that as the mechanical properties of rock sample increase,the cracking pressure of rock sample increases.The position and number of voids around the split hole will have a significant impact on the crack initiation direction and subsequent expansion path of the main crack during the hydraulic fracturing process.During the expansion process of the main crack,it will produce a position towards or near the void surrounding the split hole.Secondary cracks.Directional perforation cracking can control the crack growth in the expected direction,achieving a fast and accurate cracking of the roadway section.Based on the extended finite element theory,combined with hydraulic fracture test research,ABAQUS software was used to establish a numerical simulation model of hydraulic cracking,and further study was made on the hydraulic fracturing crack propagation law and the maximum principal stress distribution cloud diagram under different confining pressure parameters and different directional perforation angles.Numerical simulation results show that the hydraulic fracturing process is divided into four stages: fissure initiation,sporadic development,uniform expansion and fracturing termination.The crack initiation and propagation are mainly controlled by tensile failure,and the initiation pressure varies with the coefficient and orientation of the surrounding pressure difference.The perforation azimuth increases.Under the condition of the same confining pressure difference coefficient,the crack propagation length decreases with the increase of the directional perforation azimuth angle.Under the same directional perforation azimuth angle,the crack propagation length increases with the confining pressure difference coefficient.And increase.Under the condition of the same confining pressure difference coefficient,the turning radius increases with the increase of the directional perforation azimuth angle.When the directional perforating azimuth angles are 0° and 15°,the turning radius r increases with the confining pressure difference coefficient.There is a small increase in the magnitude,and when the directional perforation azimuth is 30° and 45°,the turning radius decreases with the increase of the coefficient of the surrounding pressure difference.Based on the study of rock sample hydraulic cracking test,the research on rock fragmentation by hydraulic fracturing combined cutting head was carried out,and the hydraulic fracture was studied using cutting torque,propulsion force and cutting specific energy consumption during the process of rock cutting.Influence of number of voids and form of cracking on the rock breaking performance of the cutting head in the process of rock specimens.The results show that the cutting torque,propulsion force,and cutting specific energy consumption during the rock fragmentation of the cutting head are reduced with the increase of the number of cracking holes,and the main cracks produced during the cracking process are compared with those of the non-uplifted rock samples.The denser and more dense fissures are formed by the expansion and development of the pores around the upburst hole,resulting in easy cutting of the rock sample.In the overall trend,the curve of the cutting load of the uncracked rock sample is higher than that of the rock sample after the fracture,and the cutting load of the sample after the directional perforation fracture is slightly lower than that of the non-directional fractured rock.This shows that the effect of directional perforation cracking on the weakening of rock samples is better than that of non-directional cracking. |
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