In order to enhance coal recovery ratio of open pit coal mines, a new extraction method called zonal mining system for residual coal around the end-walls is presented. The mining system can improve economic benefits b...In order to enhance coal recovery ratio of open pit coal mines, a new extraction method called zonal mining system for residual coal around the end-walls is presented. The mining system can improve economic benefits by exploiting haulage and ventilation roadways from the exposed position of coal seams by uti- lizing the existing transportation systems. Moreover, the main mining parameters have also been dis- cussed. The outcome shows that the load on coal seam roof is about 0.307 MPa and the drop step of the coal seam roof about 20.3 m when the thickness of cover and average volume weight are about 120 m and 0.023 MN/m~ respectively. With the increase of mining height and width, the coal recovery ratio can be improved. However, when recovery ratio is more than 0.85, the average stress on the coal pillar will increase tempestuously, so the recovery ratio should also be controlled to make the coal seam roof safe. Based on the numerical simulation results, it is concluded that the ratio of coal pillar width to height should be more than 1.0 to make sure the coal pillars are steady, and there are only minor dis- placements on the end-walls.展开更多
The present study examines the results of the researches related to the gob bulking factor carried out at home and abroad.A mathematical function of a three-dimensional gob bulking factor is described based on a three...The present study examines the results of the researches related to the gob bulking factor carried out at home and abroad.A mathematical function of a three-dimensional gob bulking factor is described based on a three-dimensional gob model.The method of taking value for interstice and permeability ratios is also proposed.The law of air leakage of fully mechanized top coal is researched in this study.The results show that the speed of air flow near the upper and lower crossheadings is higher than that in the central section of the gob at the same distance from the working face.When the amount of air at the working face exceeds a critical amount,the width of the spontaneous combustion zone in the upper and lower crossheadings is also larger than that in the central section.In this situation,the key is preventing the coal left in the upper and lower crossheadings from self-igniting.Reducing the amount of air at the working face can decrease the width of the spontaneous combustion zone,especially the width near the upper and lower crossheadings.This also moves the spontaneous combustion zone in the direction of the working face.It can prevent the coal in the gob from self-igniting by making the coal left in the crossheadings to be inert and by effectively controlling the amount of air at the working face.展开更多
The stability control of longwall coalface is the key technology of large-cutting-height mining method.Therefore,a systematic study of the factors that affect coalface stability and its control technology is required ...The stability control of longwall coalface is the key technology of large-cutting-height mining method.Therefore,a systematic study of the factors that affect coalface stability and its control technology is required in the development of large-cutting-height mining method in China. After the practical field observation and years of study,it was found that the more than 95% of failures in coalface are shear failure. The shear failure analysis model of coalface has been established,that can perform systematic study among factors such as mining height,coal mass strength,roof load,support resistance,and face flipper protecting plate horizontal force. Meanwhile,sensitivity analysis of factors influencing coalface stability showed that improving support capacity,cohesion of coal mass and decreasing roof load of coalface are the key to improve coalface stability. Numerical simulation of the factors affecting coalface stability has been performed using UDEC software and the results are consistent with the theoretical analysis. The coalface reinforcement technology of large-cutting-height mining method using the grouting combined with coir rope is presented. Laboratory tests have been carried out to verify its reinforcement effect and practical application has been implemented in several coal mines with good results.It has now become the main technology to reduce longwall coalface failure of large-cutting-height mining method.展开更多
文摘In order to enhance coal recovery ratio of open pit coal mines, a new extraction method called zonal mining system for residual coal around the end-walls is presented. The mining system can improve economic benefits by exploiting haulage and ventilation roadways from the exposed position of coal seams by uti- lizing the existing transportation systems. Moreover, the main mining parameters have also been dis- cussed. The outcome shows that the load on coal seam roof is about 0.307 MPa and the drop step of the coal seam roof about 20.3 m when the thickness of cover and average volume weight are about 120 m and 0.023 MN/m~ respectively. With the increase of mining height and width, the coal recovery ratio can be improved. However, when recovery ratio is more than 0.85, the average stress on the coal pillar will increase tempestuously, so the recovery ratio should also be controlled to make the coal seam roof safe. Based on the numerical simulation results, it is concluded that the ratio of coal pillar width to height should be more than 1.0 to make sure the coal pillars are steady, and there are only minor dis- placements on the end-walls.
基金Financial support for this work was obtained from the National Natural Science Foundation of China(No.51074059)
文摘The present study examines the results of the researches related to the gob bulking factor carried out at home and abroad.A mathematical function of a three-dimensional gob bulking factor is described based on a three-dimensional gob model.The method of taking value for interstice and permeability ratios is also proposed.The law of air leakage of fully mechanized top coal is researched in this study.The results show that the speed of air flow near the upper and lower crossheadings is higher than that in the central section of the gob at the same distance from the working face.When the amount of air at the working face exceeds a critical amount,the width of the spontaneous combustion zone in the upper and lower crossheadings is also larger than that in the central section.In this situation,the key is preventing the coal left in the upper and lower crossheadings from self-igniting.Reducing the amount of air at the working face can decrease the width of the spontaneous combustion zone,especially the width near the upper and lower crossheadings.This also moves the spontaneous combustion zone in the direction of the working face.It can prevent the coal in the gob from self-igniting by making the coal left in the crossheadings to be inert and by effectively controlling the amount of air at the working face.
基金financial support from National Basic Research Program of China (No.2013CB227903)the National Natural Science Foundation of General Program of China (No.51574244)the Joint Funds of the National Natural Science Foundation of China (No.U1361209) are greatly appreciated
文摘The stability control of longwall coalface is the key technology of large-cutting-height mining method.Therefore,a systematic study of the factors that affect coalface stability and its control technology is required in the development of large-cutting-height mining method in China. After the practical field observation and years of study,it was found that the more than 95% of failures in coalface are shear failure. The shear failure analysis model of coalface has been established,that can perform systematic study among factors such as mining height,coal mass strength,roof load,support resistance,and face flipper protecting plate horizontal force. Meanwhile,sensitivity analysis of factors influencing coalface stability showed that improving support capacity,cohesion of coal mass and decreasing roof load of coalface are the key to improve coalface stability. Numerical simulation of the factors affecting coalface stability has been performed using UDEC software and the results are consistent with the theoretical analysis. The coalface reinforcement technology of large-cutting-height mining method using the grouting combined with coir rope is presented. Laboratory tests have been carried out to verify its reinforcement effect and practical application has been implemented in several coal mines with good results.It has now become the main technology to reduce longwall coalface failure of large-cutting-height mining method.
