基于临界稳定断面的隧道围岩稳定性分析方法探讨

为定量评价隧道围岩的稳定性并指导支护设计，提出了隧道临界稳定断面的概念及基于临界稳定断面的隧道围岩稳定性分析方法，主要包括以下内容：（1）隧道临界稳定断面就是与设计开挖断面中心埋深相同、几何形状相似在无支护状态下围岩能够自稳的最大断面；（2）当设计开挖断面小于临界稳定断面时，临界稳定断面与设计开挖断面之间的围岩可以作为支护结构利用，且当其安全系数满足设计要求时，认为围岩能够长期自稳，除进行局部防护外，不需要系统支护，否则需要补充工程支护措施；（3）当设计开挖断面大于临界稳定断面时，需要进行工程支护；（4）提出了设计支护力的计算方法，即认为破坏区范围内的围岩为松散体，设计支护力 应能维持该松散体的稳定且具有一定的安全系数。通过该方法，对两种典型断面形式的铁路隧道的临界稳定断面进行了研究，并计算了不同围岩级别、不同埋深条件下围岩的自承载安全系数与所需的工程支护力。研究成果可以为隧道围岩稳定性的量化分析、支护设计等提供一种新的思路。

Discussion on stability analysis method of tunnel surrounding rock based on critical stable section

In order to quantitatively evaluate the stability of tunnel surrounding rock and guide the support design, the concept of critical stable section of tunnel and the stability analysis method of tunnel surrounding rock based on critical stable section are proposed. The main contents are as follows: 1) The critical stable section of a tunnel is the largest section with the same central buried depth and similar geometry as the designed excavation section, and the surrounding rock can be self stable without support. 2) When the design excavation section is smaller than the critical excavation section, the surrounding rock between the critical stability section and the design excavation section can be used as a support structure; and when the safety factor meets the design requirements, it is considered that the surrounding rock can be self-stable for a long time, except for local protection, no system support is required, otherwise supplementary engineering support measures are required. 3) When the design excavation section is larger than the critical stable section, the "artificial" support is required. 4) A method for calculating the design support force is proposed, in which, the surrounding rock in the damage area is considered to be loose, and the design support force should be able to maintain the stability of the loose body with a certain safety factor. This method is employed to analyze two typical sections of the critical stable sections of railway tunnels, and to calculate the self-bearing safety factor of surrounding rock and the required ‘artificial’ support force under the conditions of different surrounding rock grades and different burial depths.