漫谈矿山法隧道技术第十讲——软弱围岩隧道中开挖断面早期闭合的施工技术

Tunneling by Mining Method: Lecture Ⅹ: Construction Technologies for Early Close of Excavation Cross-section of Tunnel in Soft and Weak Surrounding Rocks

阐述开挖断面早期闭合的概念,指出:1)开挖断面早期闭合是针对不良围岩的对策;2)围岩越差,要求闭合的时间、距离越短;3)开挖断面分部越多,闭合距离越长,对控制变形不利;4)开挖断面的早期闭合是指初期支护的闭合,而不是指二次衬砌的闭合。介绍了日本隧道早期闭合仰拱设置方法分类。认为我们已经知道如何实现早期闭合,但还没有做到,这需要机械化水平的提高、缩短单项作业时间才能做到。日本采用的开挖断面早期闭合工法已经标准化,介绍其标准模式及开挖断面早期闭合模式的内涵。通过对日本采用早期闭合工法隧道的实例统计分析,将隧道围岩早期闭合模式划分为5种,归纳了采用早期闭合工法的理由,统计了哪些围岩条件需采用早期闭合工法,并介绍了开挖断面早期闭合隧道的构造参数,以及开挖断面早期闭合隧道的施工方法。以日本七尾公路隧道为例,详细阐述全断面早期闭合施工的管理方法,包括全断面早期闭合的管理项目,最终位移值的管理基准值和初期位移速度的管理基准值及如何确定,全断面早期闭合模式的基准及如何根据施工实际进行修正。从国内外软弱围岩隧道的施工实例,特别是开挖断面早期闭合的实例中,总结软弱围岩隧道大断面施工技术的基本经验。最后指出把掌子面前方围岩的补强与掌子面后方开挖断面早期闭合结合在一起,在有水的条件下,再把掌子面前方围岩的超前钻孔预测组合在一起,是解决不良围岩隧道施工的基本方法。

The concept of early close of excavation cross-section is introduced.It is pointed out that：1）The early close of excavation cross-section has to be adopted in bad surrounding rocks.2）The close time and distance of excavation cross-section reduce with the surrounding rock goes worse.3）The close distance of excavation cross-section increases with partition of excavation cross-section increases.4）The early close of excavation cross-section indicates the close of primary support.The classification of setting of early closed inverted arch of tunnels in Japan is introduced.The author believes that we have to learn how to improve the construction technologies so as to realize early close of excavation cross-section.The standards for early close of excavation cross-section in Japan have been perfected.The mode of the standards and concept of early close in Japan are introduced.The tunnels in Japan,adopting early close of excavation cross-section,are introduced.The early close modes of excavation cross-section are divided into 5 kinds.The rationality of adopting early close of excavation cross-section is summarized.The surrounding rock conditions in which early close of excavation cross-section has to be adopted are summarized.The structural parameters and construction technologies of tunnel using early close of excavation cross-section are introduced.The construction management methods of early close of excavation cross-section of Qiwei Tunnel in Japan,including management items,final displacement management standards,primary displacement speed management standards,early close modes and related modification, are＆nbsp;introduced in detail.The construction technologies for large-cross-section tunnel in soft and weak surrounding rocks are summarized.The combination method of reinforcement of surrounding rock ahead of excavation face and early close of excavation cross-section,together with advance geological prediction hole drilling （under condition of water）,are the basic methods for construction of bad surrounding rocks.