基于关键块体理论的隧道分部施工时空效应

Time-space effect in fractional steps construction tunnels by key block theory

分部台阶施工的隧道开挖所形成关键块体因不同工序下临空面的位置、大小及开挖时机的不同而存在时空效应。阐述了关键块体时空效应的概念,并以福州长乐国际机场高速公路二期双向8车道特大跨度连拱隧道为依托,给出了时空效应概念及其工程应用;提出了关键块体所产生的时空效应应用的基本原则。结果表明:在采用双侧壁导坑施工的隧道中,预留核心部分岩体有利于隧道顶部块体的稳定;隧道施工时,减小开挖临空面面积能有效控制关键块体的体积,及时支护能减小因蠕变而导致的块体节理面力学性质的削弱;以时空效应应用基本原则为指导,将其应用于隧道开挖过程可省去部分临时支护,同时可提高隧道施工的安全性和经济性。

The key block＇s time-space effect is existed because of the location or the size and the time of the key block when the tunnel was excavated in fractional steps construction.The definition of time-space effect of the key block is described,and then based on the Jinjishan tunnel which is extra-large eight spans multi-arch tunnel in the second stage of the Fuzhou Changle international airport highway project,the definition and the application of the time-space effect is explained in detail.The basic application principle of the time-space effect of key block is put forward.The analysis shows that the stability of the upper blocks in the tunnel could be improved by reservating the core part rock in the two side-wall pilot tunnel,the key block volume could be controlled by limiting the free face area,the mechanic properties of the joints could be weaken caused by creeping because of supported in time,and the temporary support could be reduced by the application of the guiding fundamental principles of key block,so that the safety and the economic efficiency are raised in the tunnel construction procedure.4 tabs,5 figs,14 refs.