Maintaining stability as well as optimizing recovery of crown pillar, a pillar separating surface area with the uppermost stope in overhand cut and fill underground mining method, is important. Failures in stope may l...Maintaining stability as well as optimizing recovery of crown pillar, a pillar separating surface area with the uppermost stope in overhand cut and fill underground mining method, is important. Failures in stope may lead to crown pillar failures and cause surface subsidence. Increasing crown pillar thickness will increase crown pillar stability yet reduce mining recovery because part of crown pillar is formed by ore body. Preventing stope failure is the key to maintain stability and optimize recovery of crown pillar. Therefore, it is important to study countermeasure method for stope failure especially in crown pillar area. An attempt has been made to investigate the effectiveness of various countermeasures for stope failure in crown pillar area by means of parametric study. The result shows active type support system is effective for supporting stope in high vertical stress condition while the passive one needs to be installed if the stope is opened in high horizontal stress condition. In general, more supporting capacity from both type support systems is needed if the stope is opened in more severe geological condition. Another countermeasures, sill pillar and surface pile, are introduced for stope instability in crown pillar and non-crown pillar area. Sill pillar is an abandoned slice of unstable stope based on stability analysis. Sill pillar is very effective to stabilize stope both in crown pillar and non-crown pillar area, especially for stope in high horizontal stress condition. Sill pillar application in model with stress ratio 2 can optimize 20 meter thickness of crown pillar into 5 meter. Another proposed countermeasure is surface pile. Surface pile can be installed from the surface to improve stability of crown pillar and stope. The most effective use of surface pile is found in simulation of model with stress ratio 0.75 where surface pile can optimize 15 meter thickness of crown pillar into 5 meter.展开更多
雷击是影响±500 k V直流架空输电线路运行的重要因素,±500 k V直流线路避雷器的挂网试运行成功,为直流线路防雷改造提供了有效技术手段,但大规模的工程应用仍是空白。笔者结合±500 k V江城线直流线路避雷器安装项目,研究...雷击是影响±500 k V直流架空输电线路运行的重要因素,±500 k V直流线路避雷器的挂网试运行成功,为直流线路防雷改造提供了有效技术手段,但大规模的工程应用仍是空白。笔者结合±500 k V江城线直流线路避雷器安装项目,研究了±500 k V直流线路避雷器选型、选点原则,给出了不同塔型下直流线路避雷器的安装方案,并提出直线塔宜采用悬挂式安装方案,耐张塔宜采用地面支柱式安装方案。运行数据表明,笔者提出的±500 k V直流线路避雷器选型、选点原则防雷改造效果明显,安装方案达到线路安全运行要求,对±500 k V直流线路避雷器的推广应用和在运直流线路防雷改造工作具有重要的实践和借鉴意义。展开更多
文摘Maintaining stability as well as optimizing recovery of crown pillar, a pillar separating surface area with the uppermost stope in overhand cut and fill underground mining method, is important. Failures in stope may lead to crown pillar failures and cause surface subsidence. Increasing crown pillar thickness will increase crown pillar stability yet reduce mining recovery because part of crown pillar is formed by ore body. Preventing stope failure is the key to maintain stability and optimize recovery of crown pillar. Therefore, it is important to study countermeasure method for stope failure especially in crown pillar area. An attempt has been made to investigate the effectiveness of various countermeasures for stope failure in crown pillar area by means of parametric study. The result shows active type support system is effective for supporting stope in high vertical stress condition while the passive one needs to be installed if the stope is opened in high horizontal stress condition. In general, more supporting capacity from both type support systems is needed if the stope is opened in more severe geological condition. Another countermeasures, sill pillar and surface pile, are introduced for stope instability in crown pillar and non-crown pillar area. Sill pillar is an abandoned slice of unstable stope based on stability analysis. Sill pillar is very effective to stabilize stope both in crown pillar and non-crown pillar area, especially for stope in high horizontal stress condition. Sill pillar application in model with stress ratio 2 can optimize 20 meter thickness of crown pillar into 5 meter. Another proposed countermeasure is surface pile. Surface pile can be installed from the surface to improve stability of crown pillar and stope. The most effective use of surface pile is found in simulation of model with stress ratio 0.75 where surface pile can optimize 15 meter thickness of crown pillar into 5 meter.
文摘雷击是影响±500 k V直流架空输电线路运行的重要因素,±500 k V直流线路避雷器的挂网试运行成功,为直流线路防雷改造提供了有效技术手段,但大规模的工程应用仍是空白。笔者结合±500 k V江城线直流线路避雷器安装项目,研究了±500 k V直流线路避雷器选型、选点原则,给出了不同塔型下直流线路避雷器的安装方案,并提出直线塔宜采用悬挂式安装方案,耐张塔宜采用地面支柱式安装方案。运行数据表明,笔者提出的±500 k V直流线路避雷器选型、选点原则防雷改造效果明显,安装方案达到线路安全运行要求,对±500 k V直流线路避雷器的推广应用和在运直流线路防雷改造工作具有重要的实践和借鉴意义。
