The stability of underground excavations is influenced by discontinuities interspaced in surrounding rock masses as well as the stress condition. In this work, a numerical study was undertaken on the failure behavior ...The stability of underground excavations is influenced by discontinuities interspaced in surrounding rock masses as well as the stress condition. In this work, a numerical study was undertaken on the failure behavior around a circular opening in a rock mass having non-persistent open joints using PFC software package. A parallel-bond stress corrosion(PSC) approach was incorporated to drive the failure of rock mass around the circular opening, such that the whole progressive failure process after excavation was reproduced. Based on the determined micro parameters for intact material and joint segments, the failure process around the circular opening agrees very well with that obtained through laboratory experiment. A subsequent parametric study was then carried out to look into the influence of lateral pressure coefficient, joint dip angle and joint persistency on the failure pattern and crack evolution of the rock mass around the circular opening. Three failure patterns identified are step path failure, planar failure and rotation failure depending on the lateral pressure coefficient. Moreover, the increment of joint dip angle and joint persistency aggravates the rock mass failure around the opening. This study offers guideline on stability estimation of underground excavations.展开更多
CO_(2)驱油是CO_(2)捕集、利用与封存(carbon capture,utilization and storage,CCUS)技术中CO_(2)地质利用环节的重要组成部分,延长油田开展CO_(2)驱油与封存项目取得了良好的增油封碳效果,但实际CO_(2)驱注入环境下的管柱腐蚀失效原...CO_(2)驱油是CO_(2)捕集、利用与封存(carbon capture,utilization and storage,CCUS)技术中CO_(2)地质利用环节的重要组成部分,延长油田开展CO_(2)驱油与封存项目取得了良好的增油封碳效果,但实际CO_(2)驱注入环境下的管柱腐蚀失效原因尚不明晰。利用扫描电镜(scanning electron microscopy,SEM)、3D共聚焦显微镜、能谱分析(energy dispersive spectrometer,EDS)、X射线衍射(X-ray diffraction spectroscopy,XRD)等实验手段对取自吴起某CO_(2)驱油与封存示范区注气管柱的腐蚀形貌进行表征,并对管柱腐蚀产物进行分析,以期明确研究区CO_(2)驱注气管柱腐蚀失效原因。结果表明:以CO_(2)腐蚀为主导的局部腐蚀造成注气管柱的腐蚀失效,腐蚀产物包括FeCO_(3)、Fe的高价氧化物及少量FeS。分析认为,低温CO_(2)的连续注入不会引起管柱腐蚀,但CO_(2)停注期间井筒温度回升、地层水上返使得注气管柱具备了发生CO_(2)/H_(2)S腐蚀的条件,且注气井转注水进一步加剧了管柱腐蚀。建议在CO_(2)停注以及转注水期间加强对注气管柱的杀菌与防腐措施。展开更多
基金Project(2013CB036003)supported by the National Basic Research Program of ChinaProjects(51374198,51134001,51404255)supported by the National Natural Science Foundation of ChinaProject(BK20150005)supported by the Natural Science Foundation of Jiangsu Province for Distinguished Youth Scholar,China
文摘The stability of underground excavations is influenced by discontinuities interspaced in surrounding rock masses as well as the stress condition. In this work, a numerical study was undertaken on the failure behavior around a circular opening in a rock mass having non-persistent open joints using PFC software package. A parallel-bond stress corrosion(PSC) approach was incorporated to drive the failure of rock mass around the circular opening, such that the whole progressive failure process after excavation was reproduced. Based on the determined micro parameters for intact material and joint segments, the failure process around the circular opening agrees very well with that obtained through laboratory experiment. A subsequent parametric study was then carried out to look into the influence of lateral pressure coefficient, joint dip angle and joint persistency on the failure pattern and crack evolution of the rock mass around the circular opening. Three failure patterns identified are step path failure, planar failure and rotation failure depending on the lateral pressure coefficient. Moreover, the increment of joint dip angle and joint persistency aggravates the rock mass failure around the opening. This study offers guideline on stability estimation of underground excavations.
文摘CO_(2)驱油是CO_(2)捕集、利用与封存(carbon capture,utilization and storage,CCUS)技术中CO_(2)地质利用环节的重要组成部分,延长油田开展CO_(2)驱油与封存项目取得了良好的增油封碳效果,但实际CO_(2)驱注入环境下的管柱腐蚀失效原因尚不明晰。利用扫描电镜(scanning electron microscopy,SEM)、3D共聚焦显微镜、能谱分析(energy dispersive spectrometer,EDS)、X射线衍射(X-ray diffraction spectroscopy,XRD)等实验手段对取自吴起某CO_(2)驱油与封存示范区注气管柱的腐蚀形貌进行表征,并对管柱腐蚀产物进行分析,以期明确研究区CO_(2)驱注气管柱腐蚀失效原因。结果表明:以CO_(2)腐蚀为主导的局部腐蚀造成注气管柱的腐蚀失效,腐蚀产物包括FeCO_(3)、Fe的高价氧化物及少量FeS。分析认为,低温CO_(2)的连续注入不会引起管柱腐蚀,但CO_(2)停注期间井筒温度回升、地层水上返使得注气管柱具备了发生CO_(2)/H_(2)S腐蚀的条件,且注气井转注水进一步加剧了管柱腐蚀。建议在CO_(2)停注以及转注水期间加强对注气管柱的杀菌与防腐措施。
