【作者】 李健；

【导师】 谭忠盛；

【作者基本信息】 北京交通大学 ， 桥梁与隧道工程， 2012， 博士

【摘要】 随着我国高速铁路的飞速发展,相应的基础建设经验、理论也随之迅速发展。已修建并投入运营的郑西高速铁路包含有总计38座隧道、总长77km,隧道开挖断面达170m2左右。虽然此前我国有较为丰富的黄土铁路隧道修建经验,但是尚未有隧道单洞开挖面积达170m2的先例。对于这种环境下的隧道工程,如果采用之前的隧道设计理念,以经验设计为主,将很难保证能根据不同围岩地质条件,选择合理的开挖方法、超前支护、初期支护、以及有效地控制地层移动和地表沉降的技术。现有的黄土隧道设计理念将严重制约隧道建设的科学化、规范化,会直接影响隧道工程及既有地面构筑物的安全性、经济性。本文以郑西线黄土隧道洞群为依托工程,对大断面黄土隧道的支护作用机理及变形特征进行系统深入的研究,得到以下主要研究成果：(1)分别在深埋、浅埋大断面黄土隧道开展隧道变形特征研究。分别在深、浅埋大断面黄土隧道设置地表与洞内位移现场监测试验段,通过分析现场监测数据发现,浅埋段黄土隧道施工引起的地表沉降量大,而且难以控制,地表易出现裂缝,无论深浅埋隧道拱部初期支护都呈现整体下沉的趋势,且拱脚不够稳定等。(2)分别在深埋、浅埋大断面黄土隧道开展系统锚杆作用机理研究。分别在深、浅埋黄土隧道设置有、无系统锚杆对比试验段,通过分析现场监测数据发现,对于浅埋大断面黄土隧道,拱部取消系统锚杆后,能缩短各工序的施工时间,相比设置锚杆情况下反而有利于控制围岩变形；对于深埋大断面黄土隧道,设置或不设置系统锚杆下围岩变形量相当。采用理论分析手段,基于围岩变形理论及锚杆中性点理论研究黄土隧道锚杆—围岩的相互作用机制,发现黄土隧道拱部与边墙位移分布模式存在显著的不同,从而导致了锚杆在隧道不同位置处,作用不同。基于锚杆—围岩相互作用机制及离心加载有限元分析,提出了大断面黄土隧道中锚杆设计参数。(3)在浅埋大断面黄土隧道开展不同钢架形式作用机理研究。在浅埋黄土隧道分别设置型钢钢架、格栅钢架对比试验段,现场对比试验结果表明,两种钢架初期支护变形相当；两种钢架的应力均在允许值范围之内,但格栅钢架应力较小；格栅钢架围岩—初期支护接触压力分布较均匀；两种钢架组合支护在控制大断面黄土隧道拱顶下沉方面无明显差异,型钢钢架组合支护在控制隧道初期支护水平收敛位移方面具有一定优势。基于混凝土早期强度,建立组合支护与围岩的特征曲线,研究围岩与组合支护的相互作用机制,最终得到在大断面黄土隧道中格栅钢架适用条件,以及在不同围岩条件下钢架的设计参数。(4)采用现场监测、理论分析及数值计算等手段研究浅埋大断面黄土隧道地表沉降控制技术。通过理论分析、数值计算等综合手段分析试验段监测数据,揭示了浅埋黄土隧道地层沉降变形规律,并在此基础上分析地层变形的影响因素；得到了浅埋大断面黄土隧道地表沉降控制基准；提出了减小开挖面积、侧导多台阶开挖、预留核心土、快速封闭及加强超前支护、初期支护、大拱脚等一系列沉降控制关键技术,最终保障了阌乡隧道顺利下穿连霍高速公路。更多还原

【Abstract】 With the rapid growth of high speed railway construction in China, the corresponding basic construction experiences and theory are also developing greatly. Along the Zheng-Xi High Speed Railway,38tunnels with total77km length has been constructed. The tunnel sections have significant large excavation section as170m2. Although China has many construction experiences in loess area, but no tunnel section as Zheng Xi’s has reached such big. So, if continuely follow the old design method, such as empirical design, it’s hard to choose the suitable method for construction, advanced and primary supportting, and controlling the ground settlement and deformation. Undoubtedly, the existing design theory in loess area will restrict seriously the scientificity and standardlization of loess tunnel construction, and further have direct influence on the tunnel and the ground structures’security and economical efficiency. Based on the loess tunnel construction in Zheng-Xi High Speed Railway, systematic deep research on the deformation features of tunnel and tunnel supporting mechanism, has been done; and the most important conclusions are summarized as follow:(1) The deformation feature research on deep buried and shallow large section loess tunnel:According to field monitoring data, it is found that the ground settlement caused by the construction exceeds the allowable design value a lot; the settlement is hard to control but will easy cause ground crack; the support of tunnel has integral sinking both in deep buried and shallow tunnel, and also the arch springing isn’t steady, etc.(2) The system bolts mechanism research deep buried and shallow large section loess tunnel:According to field monitoring data, it is found that cancelling the system bolts is more propitious than with system bolts to control the deformation of soil because of curtailing the construction time of different process in shallow large section loess tunnel; But for deep buried large section loess tunnel, with or without system bolts doesn’t has influence on section deformation. Based on the theory of soil deformation and neutral point theory of bolt, the study indicates that the different distribution model of displacement lead to bolts play different role in different position of tunnel. Based on soil mechanism, bolt mechanism and the method of centrifugal loading finite element, designing parameter for system bolt in large section loess tunnel has been presented in dissertation. (3) The comparison of grid steel frame and section steel frame in shallow large section loess tunnel:The result indicates that the deformation of the two supports are almost equivalent; both the stresses of the two supporting forms are in the range of allowable value, but the stresses of grid steel frame is lesser than the section steel frame’s; the earth pressure distribution in grid steel frame is better than the section steel frame’s; there isn’t any obvious differences between the two supports to control the vault crown settlement of tunnel, but the section steel frame has some advantages to control the horizontal convergence of tunnel. Based on the early strength of concrete, the support characteristic curves combined both supporting forms and ground response curve have been developed to study the mechanism between soil and support, and finally the applicable condition and design parameters for the different steel frame have been developed.(4) Ground surface settlement controlling technology of shallow large section loess: According to the field monitoring data, the law of soil deformation above the shallow large section loess tunnel and the influence factors to the deformation have been presented; also the control criterion for ground surface settlement of shallow Large section loess Tunnel is set up by research; Aseries of key technologies to control the settlement, such as reducing excavation area, increasing excavation steps of pilot tunnel, reserving core soil, quick closure, reinforcing primary support, big arch springing, etc, has been proposed and used successfully in the LianHuo Highway underpass Project.更多还原