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为特殊照明和交通安全在世界最长的双峒公路隧道——秦岭终南山隧道内设计了6个峒室,该隧道穿越中国陕西省秦岭山脉,最大埋深达1 800 m。在峒址附近的2个位置采用应力解除法量测岩石地应力,该处的岩石覆盖厚度分别为1 600和400 m,量测结果显示极高的地应力。为满足照明和行车安全的要求,每个峒室设计成纺锤型,长度为200 m,最大宽度为22 m。受到已建成隧道的限制,两峒室间最小岩柱厚度只有8 m。峒室的主要特征为:(1)高地应力;(2)岩石条件较好;(3)与峒室尺寸相比岩柱厚度很小,这些特征对围岩支护提出极大的挑战。围岩支护是依据岩体分类Q系统采用经验法设计,然后采用数值分析校核。临时支护和永久支护系统均采用喷射混凝土和锚杆。为保证施工和运行期的峒室稳定提出一整套实施程序,包括开挖、喷射混凝土、安装锚杆和监控措施。对于极高地应力区域的峒室采用柔性支护,允许岩体在永久支护安装前发生部分变形,从而保证峒室稳定及支护元件安全可靠地发挥效用。分别采用FLAC3D和Phase 2程序进行三维和二维数值分析,三维计算主要用于研究峒室的整体稳定及沿隧道轴向的三维效应;二维计算用于详细研究施工顺序和各支护单元的功效。数值分析显示喷射混凝土和锚杆在各施工阶段都能安全运作,从而验证了围岩支护设计。
Designed for special lighting and traffic safety The world’s longest double-ridge highway tunnel in the world - Qinling Zhongnanshan tunnel designed six chambers, the tunnel through the Qinling Mountains in Shaanxi Province, China, the maximum depth of 1 800 m. Stress relief was used to measure the rock stress at two locations near the site, where the rock cover thickness was 1 600 and 400 m, respectively. The measurements showed extremely high in-situ stress. To meet lighting and driving safety requirements, each chamber is designed as a spindle with a length of 200 m and a maximum width of 22 m. Due to the restrictions of the completed tunnels, the minimum pillar thickness between the two towers is only 8 m. (1) High ground stress; (2) Rock condition is better; (3) Rock pillar thickness is very small compared with the size of the salamander, which poses a great challenge to the surrounding rock support. Surrounding rock support is based on rock mass classification Q system using empirical design, and then use numerical analysis check. Both temporary support and permanent support systems use shotcrete and rock bolts. In order to ensure the stability of the construction and operation of the chamber proposed a set of implementation procedures, including excavation, shotcrete, installation of anchors and monitoring measures. Flexible support is applied to the plenum in extremely high stress areas to allow partial deformation of the rock mass before permanent support is installed, thus ensuring the stability of the pylon and the safe and reliable support elements. Three-dimensional and two-dimensional numerical analysis are respectively carried out by FLAC3D and Phase 2 programs. The three-dimensional calculation is mainly used for the study of the overall stability and the three-dimensional effect along the tunnel axis. The two-dimensional calculation is used to study the construction sequence and each supporting unit in detail effect. Numerical analysis shows that shotcrete and bolt can work safely in all construction stages, thus verifying the design of surrounding rock support.