Based on the analyses of data obtained from the underground powerhouse at Jinping I hydropower station, a comprehensive review of engineering rock mechanics practice in the underground powerhouse is first conducted. T...Based on the analyses of data obtained from the underground powerhouse at Jinping I hydropower station, a comprehensive review of engineering rock mechanics practice in the underground powerhouse is first conducted. The distribution of strata, lithology, and initial geo-stress, the excavation process and corresponding rock mass support measures, the deformation and failure characteristics of the surrounding rock mass, the stress characteristics of anchorage structures in the cavern complex, and numerical simulations of surrounding rock mass stability and anchor support performance are presented. The results indicate that the underground powerhouse of Jinping I hydropower station is characterized by high to extremely high geo-stresses during rock excavation. Excessive surrounding rock mass deformation and high stress of anchorage structures, surrounding rock mass unloading damage, and local cracking failure of surrounding rock masses, etc., are mainly caused by rock mass excavation. Deformations of surrounding rock masses and stresses in anchorage structures here are larger than those found elsewhere： 20% of extensometers in the main powerhouse record more than 50 mm with the maximum at around 250 mm observed in the downstream sidewall of the transformer hall. There are about 25% of the anchor bolts having recorded stresses of more than 200 MPa. Jinping I hydropower plant is the first to have an underground powerhouse construction conducted in host rocks under extremely high geo-stress conditions, with the ratio of rock mass strength to geo-stress of less than 2.0. The results can provide a reference to underground powerhouse construction in similar geological conditions.展开更多
Pre-existing discontinuities change the mechanical properties of rock masses,and further influence failure behavior around an underground opening.In present study,the failure behavior in both Inner and Outer zones aro...Pre-existing discontinuities change the mechanical properties of rock masses,and further influence failure behavior around an underground opening.In present study,the failure behavior in both Inner and Outer zones around a circular opening in a non-persistently jointed rock mass under biaxial compression was investigated through numerical simulations.First,the micro parameters of the PFC^(3D) model were carefully calibrated using the macro mechanical properties determined in physical experiments implemented on jointed rock models.Then,a parametrical study was undertaken of the effect of stress condition,joint dip angle and joint persistency.Under low initial stress,the confining stress improves the mechanical behavior of the surrounding rock masses;while under high initial stress,the surrounding rock mass failed immediately following excavation.At small dip angles the cracks around the circular opening developed generally outwards in a step-path failure pattern;whereas,at high dip angles the surrounding rock mass failed in an instantaneous intact rock failure pattern.Moreover,the stability of the rock mass around the circular opening deteriorated significantly with increasing joint persistency.展开更多
Underground space utilization and exploration is an irreversible trend for promoting sustainable development especially in megacities.Geotechnical engineering safety is always one of the most important issues in all p...Underground space utilization and exploration is an irreversible trend for promoting sustainable development especially in megacities.Geotechnical engineering safety is always one of the most important issues in all phases,including planning,design, construction and operation,of the underground project.Engineering geological and hydro-geological characteristics of the foundation rock mass展开更多
The heat How generated from the infinite rock mass surrounding the underground tunnels is a major cause for the increasing cooling demands in deep mine tunnels.Insulation layers with lower thermal conductivities on tu...The heat How generated from the infinite rock mass surrounding the underground tunnels is a major cause for the increasing cooling demands in deep mine tunnels.Insulation layers with lower thermal conductivities on tunnel walls and roof ceilings are believed to supply a thermo-barrier for heat abatement.However,it is found that no systematic theoretical investigations were made to predict and confirm the effectiveness of underground thermal insulation.Specifically,investigations on the underground insulation problems involving heat flows through the semi-infinite hot rock mass and insulation layer were not sufficient.Thus,in this paper,the thermal characteristics,accompanied with heat flow through the semi-infinite rock mass and the insulation layer,were modeled by both analytical and numerical methods with focus on underground mine tunnels.The close agreements between models have indicated that the thermal insulation applied on tunnel surfaces is able to provide promising heat abatement effects.展开更多
针对在复杂环境下利用钻探取芯的传统勘察方法探测地下岩土体结构特征信息存在精度低、地层结构识别准确度不高、数字化程度低等问题,依托某地铁站工程开展了钻孔多属性测试分析,得到了勘察区的孔壁影像、钻孔岩体波速及岩芯室内物理力...针对在复杂环境下利用钻探取芯的传统勘察方法探测地下岩土体结构特征信息存在精度低、地层结构识别准确度不高、数字化程度低等问题,依托某地铁站工程开展了钻孔多属性测试分析,得到了勘察区的孔壁影像、钻孔岩体波速及岩芯室内物理力学性质等数据,定量化分析了钻孔揭示的地下岩体结构面产状和宽度特征,评价了勘察区的地下岩体质量。结果表明:勘察区的地下岩体结构面产状近水平,存在两组主要走向,即NE(40°~60°)走向、NWW走向(280°~300°),其中前者与该区域的构造线方向基本一致,以构造节理、层面为主;地下岩体整体上呈砂质泥岩和砂岩互层,局部存在结构面发育带,根据孔壁岩体质量(Wall Rock Quality Designation,WRQD)指标,岩体质量较好及以上的比例为83.1%;勘察区岩体较完整,岩体质量较好,岩体基本质量分级为Ⅲ~Ⅳ。基于“点—线—面—体”相结合的钻孔多属性测试,为勘察区地下岩体工程地质信息综合评价提供了一种多手段综合勘探方法。展开更多
基金the valuable support from Yalong River Hydropower Development Company,Ltd.HydroChina Chengdu Engineering Corporation,Ltdthe National Natural Science Foundation of China(Grant Nos.51179014,51579016,51379022,and 51539002)
文摘Based on the analyses of data obtained from the underground powerhouse at Jinping I hydropower station, a comprehensive review of engineering rock mechanics practice in the underground powerhouse is first conducted. The distribution of strata, lithology, and initial geo-stress, the excavation process and corresponding rock mass support measures, the deformation and failure characteristics of the surrounding rock mass, the stress characteristics of anchorage structures in the cavern complex, and numerical simulations of surrounding rock mass stability and anchor support performance are presented. The results indicate that the underground powerhouse of Jinping I hydropower station is characterized by high to extremely high geo-stresses during rock excavation. Excessive surrounding rock mass deformation and high stress of anchorage structures, surrounding rock mass unloading damage, and local cracking failure of surrounding rock masses, etc., are mainly caused by rock mass excavation. Deformations of surrounding rock masses and stresses in anchorage structures here are larger than those found elsewhere： 20% of extensometers in the main powerhouse record more than 50 mm with the maximum at around 250 mm observed in the downstream sidewall of the transformer hall. There are about 25% of the anchor bolts having recorded stresses of more than 200 MPa. Jinping I hydropower plant is the first to have an underground powerhouse construction conducted in host rocks under extremely high geo-stress conditions, with the ratio of rock mass strength to geo-stress of less than 2.0. The results can provide a reference to underground powerhouse construction in similar geological conditions.
基金supported by the National Basic Research Program of China (No.2013CB036003)the Graduate Research and Innovation Program of Jiangsu Province (No.CXLX13_943)
文摘Pre-existing discontinuities change the mechanical properties of rock masses,and further influence failure behavior around an underground opening.In present study,the failure behavior in both Inner and Outer zones around a circular opening in a non-persistently jointed rock mass under biaxial compression was investigated through numerical simulations.First,the micro parameters of the PFC^(3D) model were carefully calibrated using the macro mechanical properties determined in physical experiments implemented on jointed rock models.Then,a parametrical study was undertaken of the effect of stress condition,joint dip angle and joint persistency.Under low initial stress,the confining stress improves the mechanical behavior of the surrounding rock masses;while under high initial stress,the surrounding rock mass failed immediately following excavation.At small dip angles the cracks around the circular opening developed generally outwards in a step-path failure pattern;whereas,at high dip angles the surrounding rock mass failed in an instantaneous intact rock failure pattern.Moreover,the stability of the rock mass around the circular opening deteriorated significantly with increasing joint persistency.
文摘Underground space utilization and exploration is an irreversible trend for promoting sustainable development especially in megacities.Geotechnical engineering safety is always one of the most important issues in all phases,including planning,design, construction and operation,of the underground project.Engineering geological and hydro-geological characteristics of the foundation rock mass
基金The financial support from an Engage Grant in the Natural Sciences and Engineering Research Council(NSERC),Canada,is gratefully acknowledged
文摘The heat How generated from the infinite rock mass surrounding the underground tunnels is a major cause for the increasing cooling demands in deep mine tunnels.Insulation layers with lower thermal conductivities on tunnel walls and roof ceilings are believed to supply a thermo-barrier for heat abatement.However,it is found that no systematic theoretical investigations were made to predict and confirm the effectiveness of underground thermal insulation.Specifically,investigations on the underground insulation problems involving heat flows through the semi-infinite hot rock mass and insulation layer were not sufficient.Thus,in this paper,the thermal characteristics,accompanied with heat flow through the semi-infinite rock mass and the insulation layer,were modeled by both analytical and numerical methods with focus on underground mine tunnels.The close agreements between models have indicated that the thermal insulation applied on tunnel surfaces is able to provide promising heat abatement effects.
文摘针对在复杂环境下利用钻探取芯的传统勘察方法探测地下岩土体结构特征信息存在精度低、地层结构识别准确度不高、数字化程度低等问题,依托某地铁站工程开展了钻孔多属性测试分析,得到了勘察区的孔壁影像、钻孔岩体波速及岩芯室内物理力学性质等数据,定量化分析了钻孔揭示的地下岩体结构面产状和宽度特征,评价了勘察区的地下岩体质量。结果表明:勘察区的地下岩体结构面产状近水平,存在两组主要走向,即NE(40°~60°)走向、NWW走向(280°~300°),其中前者与该区域的构造线方向基本一致,以构造节理、层面为主;地下岩体整体上呈砂质泥岩和砂岩互层,局部存在结构面发育带,根据孔壁岩体质量(Wall Rock Quality Designation,WRQD)指标,岩体质量较好及以上的比例为83.1%;勘察区岩体较完整,岩体质量较好,岩体基本质量分级为Ⅲ~Ⅳ。基于“点—线—面—体”相结合的钻孔多属性测试,为勘察区地下岩体工程地质信息综合评价提供了一种多手段综合勘探方法。
