摘要
以国内罕见的大帽山原位2扩4隧道为工程背景,分析CD工法下不同围岩的地表下沉、拱顶沉降、洞周收敛等现场监控量测结果,建立隧道扩建施工过程的三维弹塑性有限元模型,研究CD工法开挖时软弱围岩的稳定性。并将数值计算结果同现场量测值进行对比,其结果在数值和变形规律上基本吻合,表明本文建立的数值模型是可行的。在此基础上,提出锚杆支护参数的优化建议。相较于常规隧道,小净距隧道原位2扩4围岩变形特性如下:①软弱围岩洞口段地表沉降曲线两头小、中间大,并在既有隧道正上方出现一个微小的沉降槽;地表的总位移量主要是由于上半断面的开挖引起。②周边收敛变形和拱顶下沉有振荡特征,洞壁围岩并不是一直朝净空移动。隧道拱顶处围岩最终累积下沉量为5.72mm,仰拱主要表现为向上的隆起。③隧道原位扩挖导致既有隧道横断面产生不同程度的变形,拱脚、拱腰、拱顶等部位的最终沉降不等且依次减小,左侧的变形相对右侧较大,整个断面呈现明显的偏压状态。研究结果对日益增多的隧道扩建施工时围岩稳定性的进一步研究提供参考。
Taking the uncommon two-to-four Damaoshan tunnel as background, the stability of soft surrounding rocks by CD method is studied based on the monitoring results of surface settlement, crown settlement and eonvergement of different surrounding rocks and the three-dimensional elastic-plastic finite element model. The tested deformation results agree well with the computed ones, which proves the feasibility of the proposed analysis model. On the basis of analysis results, optimization advice of supporting parameters is put forward. Compared to the regular tunnels, the deformation characteristics of the surrounding rocks of two-to-four four lane tunnels with small clear-distance are as follows： （~） Curves of the surface settlement are presented small in both ends while big in the middle. A tiny settlement appears above the existing tunnel on the soft surrounding rocks and the total displacement of the surface is mainly caused by the construction of the up-stage. （~） The deformation of the convergement and crown settlement oscillate and the wall rock moves towards the clearance. The accumulative crown settlement is 5.72mm and the settlement at the bottom is upward. （~） Tunnel expansion will influence the existing tunnel, causing differential degrees of deformation. The total settlements on arch, arch back, crown are not equal and reduce in turn. The entire section shows bias with deformation on left side greater than that of the right . The research results can provide reference to the further research on the surrounding rocks construction stability of tunnel expansion.
出处
《土木工程学报》
EI
CSCD
北大核心
2013年第7期124-132,共9页
China Civil Engineering Journal
基金
福建省交通科技发展项目(200910)
国家自然科学青年基金(51109084)
关键词
小净距隧道
隧道原位扩建
围岩稳定性
数值模拟
监控量测
small clear-distance tunnel
tunnel expansion in situ
surrounding rocks stability
numerical simulation
site monitoring
