隧道稳定性分析与设计方法讲座之三：隧道设计理念与方法

本文作为一个讲座对以往研究成果作一综述。回顾了当前采用的3种隧道设计方法，提出了基于数值极限分析的地层－结构法，克服了地层－结构法缺点，可以求得设计所需的围岩稳定安全系数，解决了当前设计中的人为性问题。对隧道深浅埋分界线进行了探索，叙述了基于散体理论的隧洞深浅埋分界标准。提出了基于弹塑性理论的隧洞深浅埋分界标准，并对2种分解标准的优缺点进行了评述。阐述了隧道设计计算的5个基本理念： 1）隧道设计必须满足运行和施工中安全要求，提出初期支护后围岩安全系数必须保证施工安全； 2）隧道设计计算模型必须适应不同工程地质条件、围岩压力特征，符合隧道实际受力情况； 3）必须符合现代围岩压力理论与现代支护原理，充分发挥围岩自承作用； 4）隧道结构计算模型也应符合结构实际受力状态，树立初期支护作为围岩加固材料，按塑性理论计算的新理念； 5）采用合理的计算方法与计算参数，确保隧道设计计算的科学性。最后以一个地铁车站为例，采用本讲座提出的方法介绍了Ⅱ、Ⅲ、Ⅴ级围岩中隧道的设计方法与成果。

Tunnel Design Idea and Tunnel Design Method

The paper reviews three tunnel design methods used at present and puts forward the stratum structure method based on numerical limit analysis. The method can work out the safety factor of surrounding rock needed in the design, so the current subjective problems can be solved. The paper studies the separatrix between shallow tunnels and deep tunnels and also evaluates the advantages and disadvantages of the two dividing standards. Five basic ideas of tunnel design and calculation are discussed in the paper: 1) The tunnel design must satisfy the safety requirements during operation and construction and the safety factor of surrounding rock after primary support must ensure the construction safety; 2) The design and calculation model should adapt to different geological conditions, different surrounding rock pressure characteristics and different practical mechanical state of the tunnel; 3) The design and calculation of tunnel must be in accordance with the modern pressure theory of surrounding rock and supporting principle and must make full use of the self support capability of surrounding rock; 4) The tunnel structure model should also adapt to the practical mechanic state and the new idea that the primary support is the reinforcement material of surrounding rock and that calculation should be made according to the plastic theory should be established; 5) Reasonable calculation method and calculation parameters should be used to ensure scientific tunnel design and calculation. Finally, taking a subway station as an example, the paper introduces the design method of tunnels in Grade II, Grade III and Grade V surrounding rock.