In recent years,there is a scenario in urban tunnel constructions to build super-large-span tunnels for traffic diversion and route optimization purposes.However,the increased size makes tunnel support more difficult....In recent years,there is a scenario in urban tunnel constructions to build super-large-span tunnels for traffic diversion and route optimization purposes.However,the increased size makes tunnel support more difficult.Unfortunately,there are few studies on the failure and support mechanism of the surrounding rocks in the excavation of supported tunnel,while most model tests of super-large-span tunnels focus on the failure characteristics of surrounding rocks in tunnel excavation without supports.Based on excavation compensation method(ECM),model tests of a super-large-span tunnel excavation by different anchor cable support methods in the initial support stage were carried out.The results indicate that during excavation of super-large-span tunnel,the stress and displacement of the shallow surrounding rocks decrease,following a step-shape pattern,and the tunnel failure is mainly concentrated on the vault and spandrel areas.Compared with conventional anchor cable supports,the NPR(negative Poisson’s ratio)anchor cable support is more suitable for the initial support stage of the super-large-span tunnels.The tunnel support theory,model test materials,methods,and the results obtained in this study could provide references for study of similar super-large-span tunnels。展开更多
Although super-large-span tunnels ensure convenient transportation,they face many support challenges.The lack of normative construction guidance and the limited number of reference engineering cases pose a significant...Although super-large-span tunnels ensure convenient transportation,they face many support challenges.The lack of normative construction guidance and the limited number of reference engineering cases pose a significant challenge to the stability control of superlarge-span tunnels.Based on the geological conditions of a super-large-span tunnel(span=32.17 m)at the bifurcation section of the Shenzhen interchange,this study determined support parameters via theoretical calculation,numerical simulation,and engineering analogy.The support effects of negative Poisson’s ratio(NPR)anchor cables and ordinary anchor cables on super-long-span tunnels were simulated and studied.Further,based on FLAC3D simulations,the surrounding rock stress field of NPR anchor cables was analyzed under different prestressing conditions,and the mechanism of a long-short combination,high-prestress compensation NPR anchor cable support was revealed.On the basis of numerical simulations,to our knowledge,the three-dimensional(3D)geomechanical model test of the NPR anchor cable and ordinary anchor cable support for super-large-span tunnel excavation is conducted for the first time,revealing the stress evolution law of super-large-span tunnels,deformation and failure characteristics of the surrounding rock,and the changing trend of the anchor cable’s axial force,and verifies that NPR anchor cables with high preloads are suitable for super-large-span tunnel support and have advantages over ordinary anchor cables.This study can provide a reliable theoretical reference for the support design and stability control of the surrounding rock of similar shallow-buried super-large-span tunnels.展开更多
针对目前应用最为广泛的交联聚乙烯(Crosslinked Polyethylene,XLPE)绝缘电缆,梳理了几种常用的耐压试验方法,分析了其工作原理,并介绍了几种试验各自特点以及应用范围。通过一次110 k V/7 km电缆交流耐压试验方案,指出并联补偿串联谐...针对目前应用最为广泛的交联聚乙烯(Crosslinked Polyethylene,XLPE)绝缘电缆,梳理了几种常用的耐压试验方法,分析了其工作原理,并介绍了几种试验各自特点以及应用范围。通过一次110 k V/7 km电缆交流耐压试验方案,指出并联补偿串联谐振交流耐压试验能够增加试验装置的灵活性,在有效减小回路电流的同时,降低试验对设备容量的要求,给出高电压、长距离电缆耐压试验现场试验应注意的一些问题,为以后试验提供参考。展开更多
基金supported by the Innovation Fund Research Project of State Key Laboratory for Geomechanics and Deep Underground Engineering,China University of Mining and Technology(Grant No.SKLGDUEK202201)the Foundation for the Opening of State Key Laboratory for Geomechanics and Deep Underground Engineering,China University of Mining and Technology(Grant No.SKLGDUEK2129)the Open Research Fund of State Key Laboratory of Geomechanics and Geotechnical Engineering,Institute of Rock and Soil Mechanics,Chinese Academy of Sciences(Grant No.Z020007)。
文摘In recent years,there is a scenario in urban tunnel constructions to build super-large-span tunnels for traffic diversion and route optimization purposes.However,the increased size makes tunnel support more difficult.Unfortunately,there are few studies on the failure and support mechanism of the surrounding rocks in the excavation of supported tunnel,while most model tests of super-large-span tunnels focus on the failure characteristics of surrounding rocks in tunnel excavation without supports.Based on excavation compensation method(ECM),model tests of a super-large-span tunnel excavation by different anchor cable support methods in the initial support stage were carried out.The results indicate that during excavation of super-large-span tunnel,the stress and displacement of the shallow surrounding rocks decrease,following a step-shape pattern,and the tunnel failure is mainly concentrated on the vault and spandrel areas.Compared with conventional anchor cable supports,the NPR(negative Poisson’s ratio)anchor cable support is more suitable for the initial support stage of the super-large-span tunnels.The tunnel support theory,model test materials,methods,and the results obtained in this study could provide references for study of similar super-large-span tunnels。
基金supported by the Foundation for the Opening of State Key Laboratory for GeoMechanics&Deep Underground Engineering(Grant No.SKLGDUEK2129).
文摘Although super-large-span tunnels ensure convenient transportation,they face many support challenges.The lack of normative construction guidance and the limited number of reference engineering cases pose a significant challenge to the stability control of superlarge-span tunnels.Based on the geological conditions of a super-large-span tunnel(span=32.17 m)at the bifurcation section of the Shenzhen interchange,this study determined support parameters via theoretical calculation,numerical simulation,and engineering analogy.The support effects of negative Poisson’s ratio(NPR)anchor cables and ordinary anchor cables on super-long-span tunnels were simulated and studied.Further,based on FLAC3D simulations,the surrounding rock stress field of NPR anchor cables was analyzed under different prestressing conditions,and the mechanism of a long-short combination,high-prestress compensation NPR anchor cable support was revealed.On the basis of numerical simulations,to our knowledge,the three-dimensional(3D)geomechanical model test of the NPR anchor cable and ordinary anchor cable support for super-large-span tunnel excavation is conducted for the first time,revealing the stress evolution law of super-large-span tunnels,deformation and failure characteristics of the surrounding rock,and the changing trend of the anchor cable’s axial force,and verifies that NPR anchor cables with high preloads are suitable for super-large-span tunnel support and have advantages over ordinary anchor cables.This study can provide a reliable theoretical reference for the support design and stability control of the surrounding rock of similar shallow-buried super-large-span tunnels.
文摘针对目前应用最为广泛的交联聚乙烯(Crosslinked Polyethylene,XLPE)绝缘电缆,梳理了几种常用的耐压试验方法,分析了其工作原理,并介绍了几种试验各自特点以及应用范围。通过一次110 k V/7 km电缆交流耐压试验方案,指出并联补偿串联谐振交流耐压试验能够增加试验装置的灵活性,在有效减小回路电流的同时,降低试验对设备容量的要求,给出高电压、长距离电缆耐压试验现场试验应注意的一些问题,为以后试验提供参考。
