It is difficult to accurately calculate the lump coal rate in a fully mechanized mining face.Therefore,a numerical simulation of the coal wall cutting process,which revealed the crack expansion,development,evolution i...It is difficult to accurately calculate the lump coal rate in a fully mechanized mining face.Therefore,a numerical simulation of the coal wall cutting process,which revealed the crack expansion,development,evolution in the coal body and the corresponding lump coal formation mechanism,was performed in PFC2D.Moreover,a correlation was established between the cutting force and lump coal formation,and a statistical analysis method was proposed to determine the lump coal rate.The following conclusions are drawn from the results:(1)Based on a soft ball model,a coal wall cutting model is established.By setting the roller parameters based on linear bonding and simulating the roller cutting process of the coal body,the coal wall cutting process is effectively simulated,and accurate lump coal rate statistics are provided.(2)Under the cutting stress,the coal body in the working face underwent three stages—microfracture generation,fracture expansion,and fracture penetration—to form lump coal,in which the fracture direction is orthogonal to the cutting pressure chain.Within a certain range from the roller,as the cutting depth of the roller increased,the number of new fractures in the coal body first increases and then stabilizes.(3)Under the cutting stress,the fractured coal body is locally compressed,thereby forming a compact core.The formation and destruction of the compact core causes fluctuations in the cutting force.The fluctuation amplitude is positively related to the coal mass.(4)Because the simulation does not consider secondary damage in the coal,the simulated lump coal rate is larger than the actual lump coal rate in the working face;this deviation is mainly concentrated in large lump coal with a diameter greater than 300 mm.展开更多
The matching relationship between coal cutting and caving in fully mechanized top-coal caving face is analyzed in detail from the angle of reliability. The coupling equation of reliability is established corresponding...The matching relationship between coal cutting and caving in fully mechanized top-coal caving face is analyzed in detail from the angle of reliability. The coupling equation of reliability is established correspondingly, and the mathematical equation of the coefficient of velocity matching of coal cutting and caving is obtained, which meets a certain reliability demand for making the working procedure of coal caving not influence coal cutting of coal-cutter. The results show that the relationship between the coefficient of the velocity matching and the reliability of coal cutting and caving system is linear on the whole when R <0.9. It is pointed out that different numerical value should be selected for different coal face according to different demand for reliability.展开更多
The paper analyses the stress characteristics in longwall face and its interaction with impact coal cutting, and puts forward the operation method for impact coal cotting. Similar material to the coal in particular mi...The paper analyses the stress characteristics in longwall face and its interaction with impact coal cutting, and puts forward the operation method for impact coal cotting. Similar material to the coal in particular mine was used to simulate the coal mass. Impact coal breaking test was performed on the test rig. The traveling pattern of the impact stress wave in coal and the dynamic response of impact parameters on coal property is analyzed.展开更多
基金The funding was supported by National Natural Science Foundation of China(No.51974294).
文摘It is difficult to accurately calculate the lump coal rate in a fully mechanized mining face.Therefore,a numerical simulation of the coal wall cutting process,which revealed the crack expansion,development,evolution in the coal body and the corresponding lump coal formation mechanism,was performed in PFC2D.Moreover,a correlation was established between the cutting force and lump coal formation,and a statistical analysis method was proposed to determine the lump coal rate.The following conclusions are drawn from the results:(1)Based on a soft ball model,a coal wall cutting model is established.By setting the roller parameters based on linear bonding and simulating the roller cutting process of the coal body,the coal wall cutting process is effectively simulated,and accurate lump coal rate statistics are provided.(2)Under the cutting stress,the coal body in the working face underwent three stages—microfracture generation,fracture expansion,and fracture penetration—to form lump coal,in which the fracture direction is orthogonal to the cutting pressure chain.Within a certain range from the roller,as the cutting depth of the roller increased,the number of new fractures in the coal body first increases and then stabilizes.(3)Under the cutting stress,the fractured coal body is locally compressed,thereby forming a compact core.The formation and destruction of the compact core causes fluctuations in the cutting force.The fluctuation amplitude is positively related to the coal mass.(4)Because the simulation does not consider secondary damage in the coal,the simulated lump coal rate is larger than the actual lump coal rate in the working face;this deviation is mainly concentrated in large lump coal with a diameter greater than 300 mm.
文摘The matching relationship between coal cutting and caving in fully mechanized top-coal caving face is analyzed in detail from the angle of reliability. The coupling equation of reliability is established correspondingly, and the mathematical equation of the coefficient of velocity matching of coal cutting and caving is obtained, which meets a certain reliability demand for making the working procedure of coal caving not influence coal cutting of coal-cutter. The results show that the relationship between the coefficient of the velocity matching and the reliability of coal cutting and caving system is linear on the whole when R <0.9. It is pointed out that different numerical value should be selected for different coal face according to different demand for reliability.
文摘The paper analyses the stress characteristics in longwall face and its interaction with impact coal cutting, and puts forward the operation method for impact coal cotting. Similar material to the coal in particular mine was used to simulate the coal mass. Impact coal breaking test was performed on the test rig. The traveling pattern of the impact stress wave in coal and the dynamic response of impact parameters on coal property is analyzed.
