震后千枚岩与板岩互层隧道开挖变形控制技术
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摘要
研究目的:汶川至马尔康高速公路鹧鸪山特长隧道洞身通过千枚岩与板岩交互围岩,软硬不均地质频繁突变形成交互地层,受"5·12"强震及不定余震影响,岩体褶皱曲折,层间地下水渗透软化千枚岩,而板岩节理面光滑,千枚岩软化层极易出现似"流体状态"的滑流,造成变形坍塌。为解决鹧鸪山隧道施工的变形坍塌难题,本文通过优化开挖方法和支护参数展开研究。研究结论:(1)类似地层施工应遵循"先柔后刚、先放后抗、及时封闭、径向注浆加固、控制变形"的原则;(2)千枚岩遇水极易软化流失溜坍导致较大变形,提出类似水文地质隧道开挖预留变形值宜控制在20～35 cm;(3)宜采用三台阶预留核心土法开挖,台阶长度控制在3～5 m,台阶总长控制在25 m内,仰拱初支应及时封闭成环,其与掌子面距离宜控制在25 m内;(4)超前支护宜采用自进式中空注浆锚杆加固围岩;(5)富水地段应在初支背后加密埋设环向排水管,将初支背后散水归位,同时应充分考虑隧道突涌水量和营运排水需求,确定适宜的排水沟断面尺寸;(6)本研究成果可为川藏地区类似隧道工程的设计与施工提供参考和借鉴。
Research purposes:The extra-long Zhegushan tunnel trunk of the Wenchuan-Maerkang Expressway will pass through the interaction of the phyllite and slate.The interaction was caused by the frequent mutates of uneven soft and hard geology.Influenced by the 5·12 strong earthquake and indefinite aftershocks,the rock body was folded and twisty,the phyllite was softened by the undergound water from the interaction,joint surface of slate was smooth,and slipstream like " fluid state" occurred easily at the softened layer of the phyllite,all which may cause deformation and collapse.To study the method to solve the problem of construction deformation and collapse,the excavation method and supporting parameters are optimized in this paper.Research conclusions:(1) The construction of the similar stratum should follow the principle of soft first then hard,release first then resistance,close timely,radial grouting reinforcement and control of deformation.(2) The phyllite is easy to soften,lose and slide and slump when encountering water,which will lead to a large deformation.It is proposed that the reserved deformation value of similar hydrogeological tunnel excavation should be controlled within 20～35 cm.(3) The benching tunneling construction method caverned in which the core earth is left untouched is proposed to adopted.The length of the bench is controlled within 3～5 m and total length within 25 m.The invert initial support should be closed in time to form a closed ring,which the distance to the tunnel face should be controlled within 25 m.(4) The method to use auto-placing hollow anchor bar to reinforce the surrounding rock should be adopted for forepoling.(5) For water-rich section,some annular drainage pipe should be embedded in the back of the initial support to make the casual water returns.At the same time,the tunnel inflow and operating drainage demand should be fully considered,the proper cross-section size of trench should be determined.(6) The research results can provide reference for design and construction of similar tunnel engineering at Sichuan-Tibet region.
Research purposes:The extra-long Zhegushan tunnel trunk of the Wenchuan-Maerkang Expressway will pass through the interaction of the phyllite and slate.The interaction was caused by the frequent mutates of uneven soft and hard geology.Influenced by the 5·12 strong earthquake and indefinite aftershocks,the rock body was folded and twisty,the phyllite was softened by the undergound water from the interaction,joint surface of slate was smooth,and slipstream like " fluid state" occurred easily at the softened layer of the phyllite,all which may cause deformation and collapse.To study the method to solve the problem of construction deformation and collapse,the excavation method and supporting parameters are optimized in this paper.Research conclusions:(1) The construction of the similar stratum should follow the principle of soft first then hard,release first then resistance,close timely,radial grouting reinforcement and control of deformation.(2) The phyllite is easy to soften,lose and slide and slump when encountering water,which will lead to a large deformation.It is proposed that the reserved deformation value of similar hydrogeological tunnel excavation should be controlled within 20～35 cm.(3) The benching tunneling construction method caverned in which the core earth is left untouched is proposed to adopted.The length of the bench is controlled within 3～5 m and total length within 25 m.The invert initial support should be closed in time to form a closed ring,which the distance to the tunnel face should be controlled within 25 m.(4) The method to use auto-placing hollow anchor bar to reinforce the surrounding rock should be adopted for forepoling.(5) For water-rich section,some annular drainage pipe should be embedded in the back of the initial support to make the casual water returns.At the same time,the tunnel inflow and operating drainage demand should be fully considered,the proper cross-section size of trench should be determined.(6) The research results can provide reference for design and construction of similar tunnel engineering at Sichuan-Tibet region.
引文
[1]李天斌.汶川特大地震中山岭隧道变形破坏特征及影响因素分析[J].工程地质学报,2009(6):742-751.Li Tianbin.Failure Characteristics and Influence Factor Analysis of Mountain Tunnels at Epicenter Zones of Great Wenchuan Earthquake[J].Journal of Engineering Geology,2009(6):742-751.
[2]刘泽.强震高原季节性冻土区隧道洞口浅埋段施工探讨[C]//“川藏铁路建设的挑战与对策”2016学术交流会论文集,2016:624-632.Liu Ze.The Construction Discussion on Shallow Buried Section of Tunnel Portal in the Seasonal Frozen Soil Area of Strong Earthquake[C]//The Proceedings of2016 Symposium on Challenges and Countermeasures of Sichuan-Tibet Railway Construction,2016:624-632.
[3]王明年,林国进,于丽,等.隧道抗震与减震[M].北京:科学出版社,2012.Wang Mingnian,Lin Guojin,Yu Li,etc.Tunnel Seismic and Shock Absorption[M].Beijing:Science Press,2012.
[4]彭峰,肖盛能,潘威,等.软弱围岩隧道修建新方法---核心土加固变形控制法[J].现代隧道技术,2012(3):131-137.Peng Feng,Xiao Shengneng,Pan Wei,etc.New Construction Method for Tunnels in Weak Surrounding Rock:Controlled Deformation with Core Soil Reinforcement[J].Modern Tunnelling Technology,2012(3):131-137.
[2]刘泽.强震高原季节性冻土区隧道洞口浅埋段施工探讨[C]//“川藏铁路建设的挑战与对策”2016学术交流会论文集,2016:624-632.Liu Ze.The Construction Discussion on Shallow Buried Section of Tunnel Portal in the Seasonal Frozen Soil Area of Strong Earthquake[C]//The Proceedings of2016 Symposium on Challenges and Countermeasures of Sichuan-Tibet Railway Construction,2016:624-632.
[3]王明年,林国进,于丽,等.隧道抗震与减震[M].北京:科学出版社,2012.Wang Mingnian,Lin Guojin,Yu Li,etc.Tunnel Seismic and Shock Absorption[M].Beijing:Science Press,2012.
[4]彭峰,肖盛能,潘威,等.软弱围岩隧道修建新方法---核心土加固变形控制法[J].现代隧道技术,2012(3):131-137.Peng Feng,Xiao Shengneng,Pan Wei,etc.New Construction Method for Tunnels in Weak Surrounding Rock:Controlled Deformation with Core Soil Reinforcement[J].Modern Tunnelling Technology,2012(3):131-137.