斑竹林隧道软弱围岩变形特征与控制措施研究
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摘要
近年来,我国建设了大量铁路、公路隧道。在修建过程中当隧道位于软弱、破碎段时,隧道围岩具有稳定性差、形变复杂等特点,常形成软弱围岩大变形、流变等地质灾害,往往成为整条隧道的薄弱环节和难题。因此,对软弱围岩变形特征及其控制措施研究是目前急需解决的问题。
为此,作者以斑竹林隧道软弱围岩洞段为研究对象,依据隧道施工监控量测数据,分析和总结了软弱围岩变形特征,并运用弹塑性有限元法分别对软弱围岩隧道不同开挖方式及施工过程中围岩、支护结构力学效应进行数值模拟研究,总结和论证了软弱围岩隧道支护措施和方法,主要研究成果有:
(1)对斑竹林隧道施工过程中现场监测资料进行分析,重点研究了隧道典型断面的围岩变形-时间变化曲线、围岩变形-空间变化曲线的特点及规律,对围岩变形时间效应和空间效应进行分析,得出斑竹林隧道软弱围岩变形特征有:隧道拱顶沉降变形量比周边水平收敛值大。软弱围岩大变形段表现为变形量大,拱顶偏压,围岩受到剪胀挤出,造成支护结构严重破损;Ⅳ级、Ⅴ级围岩一般在埋设测点后经历一个月后趋于稳定,而大变形段可达数月之久;各断面围岩变形-时间变化曲线主要有抛物线型和似阶梯形两种变化型式;各断面围岩变形-空间变化曲线则主要表现为抛物线型和“厂”型,斑竹林隧道围岩变形空间效应显著。
(2)对隧道软弱围岩洞口浅埋段的全断面法和台阶法以及单侧壁导坑法的开挖施工过程进行数值模拟研究,计算出三种开挖方式下每一开挖步后的围岩位移场、应力场和锚杆轴力和喷射混凝土层应力变化情况,对计算结果进行了详细分析,比较三种施工方法的优劣,结合实际和经济性考虑,得出斑竹林隧道软弱围岩洞口浅埋段开挖方式采用台阶法比较科学、合理。
根据斑竹林隧道软弱围岩施工三维数值模拟计算结果分析表明围岩变位比较显著的区域为距隧道开挖轮廓线O.5倍洞径范围内,隧道浅表围岩位移是施工中位移控制的重点;台阶法施工中拱脚处常产生应力集中,所以在实际施工中应注意加强拱底部位的支护,尽早闭合仰拱,以分担拱脚处的承受的荷载;当隧道开挖完毕后,大部分锚杆受力较小,而喷射混凝土层基本全部受到受压,最大压应力产生在边墙顶部,实际施工中常表现为该部位产生纵向裂缝,开裂、剥落,对此应及时采取补喷混凝土等措施,并加强监控量测,控制该部位受力状态的恶化。总体看,支护结构处于正常工作状态。
3)通过对不同围岩隧道支护方法的比较研究,结合各种支护措施的作用机理,从保护和加固围岩角度出发,总结和论证了斑竹林隧道软弱围岩大变形控制对策和支护措施,认为就当前支护理论的发展和施工工艺水平看,无论对于一般软弱围岩还是对于特殊地质围岩,其支护措施应以锚注支护为中心,通过结合其它辅助支护措施,如采用可缩性型钢拱架、可缩锚杆和钢纤维混凝土等措施,从而达到控制各种类型软弱围岩变形的目的。
Lots of rail way tunnels and highway tunnels had built in China in recent years. The surrounding rock has the characteristics of poor stability and complicated deformation etc, once a tunnel is constructed in weak rock. The geologic hazards as large deformation and rheology of weak rock is always being a weakness and a problem of entire tunnel. So one of the urgent problem now is the research on deformation characteristics and reinforcement measures of the weak surrounding rock.
Author studied on the weak surrounding rock of Banzhulin tunnel, analysis and sum up its deformation characteristics with the tunnel's monitoring and measuring data in construction process. And researched on the different excavation methods and mechanical effect of weak surrounding rock and lining of Banzhulin tunnel by elasto-plastic finite element method in numerical simulation. Furthermore, author demonstrated and sum up reinforcement methods and measures of the weak surrounding rock. The primary fruit is listed as follows.
(1)Three-dimensional and time effect of weak rock deformation of Banzhulin tunnel's typical cross-sections' were emphases within analysis of the monitoring and measuring data. Results show the vertical convergence deformation of tunnel's arch crown are bigger than the horizontal of tunnel's side wall. As the part of Banzhulin tunnel located in the weak rock, it had a large deformation, uneven pressure at arch crown, sheared and extruded behavior and lining damaged. The surrounding rock of IV and V distinctions were going to be stability about one month after excavation, as well as the weak surrounding rock which have large deformation taking months. The surrounding rock's deformation-time curve have parabola-style and ladder-style, but its deformation-three dimensional curve have parabola-style and "厂"style. The deformation of the surrounding rock in Banzhulin tunnel has strong three-dimensional effect.
(2) Results of full face method, step excavation method and single-side heading method numerical simulation show the heading and bench method is scientific and feat for the port of Banzhulin tunnel. According the results of three dimensional numerical simulation, the surrounding rock with marked convergence distribute in half diameter area away from excavation outline, and this is key area in construction process. Invert should be constructed quickly to reinforce intrados as the excavation of the heading and bench method cause stress concentration at most time. Most bolt have low axes force, all shotcreting bear compression stress and the top of side wall produce maximal compression stress and shotcreting will get crack along the lengthwise direction in the construction process. For controlling the stress condition of the top of side wall, monitoring and reshotcreting will be essential. Support units are safe and have a good state.
(3)To reinforce and protect the weak surrounding rock, compared with different reinforcement methods, summarized the reinforcement measures of the weak surrounding rock of Banzhulin tunnel which have large deformation, shotcrete and rock bolt inject should be basic, no matter for the weak rock or special geologic condition stratum.
为此,作者以斑竹林隧道软弱围岩洞段为研究对象,依据隧道施工监控量测数据,分析和总结了软弱围岩变形特征,并运用弹塑性有限元法分别对软弱围岩隧道不同开挖方式及施工过程中围岩、支护结构力学效应进行数值模拟研究,总结和论证了软弱围岩隧道支护措施和方法,主要研究成果有:
(1)对斑竹林隧道施工过程中现场监测资料进行分析,重点研究了隧道典型断面的围岩变形-时间变化曲线、围岩变形-空间变化曲线的特点及规律,对围岩变形时间效应和空间效应进行分析,得出斑竹林隧道软弱围岩变形特征有:隧道拱顶沉降变形量比周边水平收敛值大。软弱围岩大变形段表现为变形量大,拱顶偏压,围岩受到剪胀挤出,造成支护结构严重破损;Ⅳ级、Ⅴ级围岩一般在埋设测点后经历一个月后趋于稳定,而大变形段可达数月之久;各断面围岩变形-时间变化曲线主要有抛物线型和似阶梯形两种变化型式;各断面围岩变形-空间变化曲线则主要表现为抛物线型和“厂”型,斑竹林隧道围岩变形空间效应显著。
(2)对隧道软弱围岩洞口浅埋段的全断面法和台阶法以及单侧壁导坑法的开挖施工过程进行数值模拟研究,计算出三种开挖方式下每一开挖步后的围岩位移场、应力场和锚杆轴力和喷射混凝土层应力变化情况,对计算结果进行了详细分析,比较三种施工方法的优劣,结合实际和经济性考虑,得出斑竹林隧道软弱围岩洞口浅埋段开挖方式采用台阶法比较科学、合理。
根据斑竹林隧道软弱围岩施工三维数值模拟计算结果分析表明围岩变位比较显著的区域为距隧道开挖轮廓线O.5倍洞径范围内,隧道浅表围岩位移是施工中位移控制的重点;台阶法施工中拱脚处常产生应力集中,所以在实际施工中应注意加强拱底部位的支护,尽早闭合仰拱,以分担拱脚处的承受的荷载;当隧道开挖完毕后,大部分锚杆受力较小,而喷射混凝土层基本全部受到受压,最大压应力产生在边墙顶部,实际施工中常表现为该部位产生纵向裂缝,开裂、剥落,对此应及时采取补喷混凝土等措施,并加强监控量测,控制该部位受力状态的恶化。总体看,支护结构处于正常工作状态。
3)通过对不同围岩隧道支护方法的比较研究,结合各种支护措施的作用机理,从保护和加固围岩角度出发,总结和论证了斑竹林隧道软弱围岩大变形控制对策和支护措施,认为就当前支护理论的发展和施工工艺水平看,无论对于一般软弱围岩还是对于特殊地质围岩,其支护措施应以锚注支护为中心,通过结合其它辅助支护措施,如采用可缩性型钢拱架、可缩锚杆和钢纤维混凝土等措施,从而达到控制各种类型软弱围岩变形的目的。
Lots of rail way tunnels and highway tunnels had built in China in recent years. The surrounding rock has the characteristics of poor stability and complicated deformation etc, once a tunnel is constructed in weak rock. The geologic hazards as large deformation and rheology of weak rock is always being a weakness and a problem of entire tunnel. So one of the urgent problem now is the research on deformation characteristics and reinforcement measures of the weak surrounding rock.
Author studied on the weak surrounding rock of Banzhulin tunnel, analysis and sum up its deformation characteristics with the tunnel's monitoring and measuring data in construction process. And researched on the different excavation methods and mechanical effect of weak surrounding rock and lining of Banzhulin tunnel by elasto-plastic finite element method in numerical simulation. Furthermore, author demonstrated and sum up reinforcement methods and measures of the weak surrounding rock. The primary fruit is listed as follows.
(1)Three-dimensional and time effect of weak rock deformation of Banzhulin tunnel's typical cross-sections' were emphases within analysis of the monitoring and measuring data. Results show the vertical convergence deformation of tunnel's arch crown are bigger than the horizontal of tunnel's side wall. As the part of Banzhulin tunnel located in the weak rock, it had a large deformation, uneven pressure at arch crown, sheared and extruded behavior and lining damaged. The surrounding rock of IV and V distinctions were going to be stability about one month after excavation, as well as the weak surrounding rock which have large deformation taking months. The surrounding rock's deformation-time curve have parabola-style and ladder-style, but its deformation-three dimensional curve have parabola-style and "厂"style. The deformation of the surrounding rock in Banzhulin tunnel has strong three-dimensional effect.
(2) Results of full face method, step excavation method and single-side heading method numerical simulation show the heading and bench method is scientific and feat for the port of Banzhulin tunnel. According the results of three dimensional numerical simulation, the surrounding rock with marked convergence distribute in half diameter area away from excavation outline, and this is key area in construction process. Invert should be constructed quickly to reinforce intrados as the excavation of the heading and bench method cause stress concentration at most time. Most bolt have low axes force, all shotcreting bear compression stress and the top of side wall produce maximal compression stress and shotcreting will get crack along the lengthwise direction in the construction process. For controlling the stress condition of the top of side wall, monitoring and reshotcreting will be essential. Support units are safe and have a good state.
(3)To reinforce and protect the weak surrounding rock, compared with different reinforcement methods, summarized the reinforcement measures of the weak surrounding rock of Banzhulin tunnel which have large deformation, shotcrete and rock bolt inject should be basic, no matter for the weak rock or special geologic condition stratum.
引文
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[3]陈乐生.四川特长公路隧道的建设与展望[A].中国公路学会隧道工程分会等编.2005年全国公路隧道学术会议论文集[C].北京:人民交通出版社,2005
[4]徐则民,黄润秋.深埋特长隧道及其施工灾害[M].成都:西南交通大学出版社,2000
[5]姜云.公路隧道围岩大变形预测预报及对策研究[D].成都:成都理工大学,2006
[6]王科.家竹箐隧道地质条件及地应力特征[J].世界隧道,1998.1:11-16
[7]张社道.家竹箐隧道施工中支护大变形的整治[J].世界隧道,1997 1:7-16
[8l 张祉道,白继承.家竹箐隧道高瓦斯、大变形、大涌水的整治与对策[J].世界隧道,19981:1-10
[9]喻渝.挤压性围岩支护大变形的机理及判定方法[J].世界隧道,1998,1:46-51
[10]王思敬,黄鼎成.中国工程地质世纪成就[M].北京:地质出版社,2004
[11]何满潮,景海河,孙晓明.软岩工程力学[M].北京:科学出版社,2002
[12]何满潮,黄福昌,闫吉太主编.世纪之交软岩工程技术现状及展望[M].北京:煤炭工业出版社,1999
[13]何满潮,蒋宇静主编.中国煤矿软岩巷道支护理论与实践[M].徐州:中国矿业大学出版社.1996
[14]中华人民共和国交通部.JTG D70-2004.公路隧道设计规范[S].北京:人民交通出版社,2004.11
[15]孙钧.地下工程设计理论与实践[M].上海:上海科学技术出版社,1996
[16]孙钧,侯学渊.地下结构[M].北京:科学出版社,1988
[17]徐干成,白洪才,郑颖人等.地下工程支护结构[M].北京:中国水利水电出版社,2003
[18]李晓红.隧道新奥法及其量测技术[M].北京:科学出版社,2002
[19]L.Muller.改变对NATM的错误概念[J].地下工程,1985,5:1-3
[20]L.Muller.新奥法的基本思想和主要原则[J].地下工程,1980 6:18-25
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