In order to solve the problem of rib spalling of high coal walls in fully-mechanized（HCWFM）mines,we used the principle of damage mechanics to analyze coal wall rib spalling.The results show that coal wall rib spalli...In order to solve the problem of rib spalling of high coal walls in fully-mechanized（HCWFM）mines,we used the principle of damage mechanics to analyze coal wall rib spalling.The results show that coal wall rib spalling is,to a certain degree,a macro-performance of the development of micro-cracks.We built a mechanical model to simulate the damage to the front of coal walls,carried out theoretical calculations of the damage parameters,analyzed the effect of mining height,original cracks,seam strength,horizontal stress,vertical displacement of the coal walls and other parameters on coal wall rib spalling, which conform well with the results of our field measurements and numerical simulation.The key to control coal wall rib spalling is to control the development of cracks in coal walls.Accelerating the speed of advancing the working face,improving the setting load of support and the horizontal force of the guard board,strengthening coal walls and other technical measures can effectively reduce the degree of damage to the coal walls and control coal wall rib spalling at HCWFM faces.展开更多
According to medical literature, fracture of the first rib is quite rare and the bilateral condition is especially rare. This type of fracture is usually associated with severe intrathoracic trauma and other bony or n...According to medical literature, fracture of the first rib is quite rare and the bilateral condition is especially rare. This type of fracture is usually associated with severe intrathoracic trauma and other bony or neurovascular injuries, thus can be considered as a harbinger of major trauma. However here we present three cases of low velocity first rib fractures without any major trauma or multisystem injuries. All the three patients were treated conservatively and did well on simple analgesics and rest and had no early or late complications. It can be seen that not all the first rib fractures are associated with major trauma or multisystem injuries. There is a variant of first rib fracture with low velocity injuries which is not associated with any major complications in contrast to majority of first rib fractures associated with high velocity injuries. Causative factor of such injuries may be violent muscular contraction of scalenus anterior or serratus anterior, but not direct trauma.展开更多
基金provided by the Independent Research Fund(No.SKLCRSM09X02)the Open Research Fund of the State Key Laboratory of Coal Resources and Safety Mining (No.08KF12)the Qinglan Project of Jiangsu Province and the Graduate Students Innovation Fund of Colleges and Universities in Jiangsu(No.CX09B_120Z)
文摘In order to solve the problem of rib spalling of high coal walls in fully-mechanized（HCWFM）mines,we used the principle of damage mechanics to analyze coal wall rib spalling.The results show that coal wall rib spalling is,to a certain degree,a macro-performance of the development of micro-cracks.We built a mechanical model to simulate the damage to the front of coal walls,carried out theoretical calculations of the damage parameters,analyzed the effect of mining height,original cracks,seam strength,horizontal stress,vertical displacement of the coal walls and other parameters on coal wall rib spalling, which conform well with the results of our field measurements and numerical simulation.The key to control coal wall rib spalling is to control the development of cracks in coal walls.Accelerating the speed of advancing the working face,improving the setting load of support and the horizontal force of the guard board,strengthening coal walls and other technical measures can effectively reduce the degree of damage to the coal walls and control coal wall rib spalling at HCWFM faces.
文摘According to medical literature, fracture of the first rib is quite rare and the bilateral condition is especially rare. This type of fracture is usually associated with severe intrathoracic trauma and other bony or neurovascular injuries, thus can be considered as a harbinger of major trauma. However here we present three cases of low velocity first rib fractures without any major trauma or multisystem injuries. All the three patients were treated conservatively and did well on simple analgesics and rest and had no early or late complications. It can be seen that not all the first rib fractures are associated with major trauma or multisystem injuries. There is a variant of first rib fracture with low velocity injuries which is not associated with any major complications in contrast to majority of first rib fractures associated with high velocity injuries. Causative factor of such injuries may be violent muscular contraction of scalenus anterior or serratus anterior, but not direct trauma.
