碳质泥岩隧道侵限机理及断面恢复技术研究

Research on mechanism of intrusion limit and section restoration technology of carbonaceous mudstone tunnel

【目的】针对隧道上台阶初支侵入断面界限的问题,探讨了隧道发生侵限的机理并提出一种断面恢复方法。【方法】首先从围岩的岩性、地下水条件等方面,分析了浙江省桐庐县仰天洞隧道发生侵限的机理;然后提出整体法和逐环法两种断面恢复方法,采用Midas GTS有限元软件对两种断面恢复方法进行分析比较。【结果】逐环法施工时围岩新增位移量小,隧道拱顶沉降累计值为6 mm,BC水平测线收敛累计值为5 mm;塑性区范围相比整体法明显减小;支护结构最大应力值为16.80 MPa,支护结构承受的应力虽较大但仍处于安全状态。这表明本支护结构能发挥更强的支护效果,逐环法是较优的断面恢复方法。【结论】研究成果可为类似隧道初支侵限工程提供参考。

[Objective] In response to the problem of intrusion into the section boundary by the initial support of the upper step of the tunnel, the mechanism of intrusion into the tunnel was discussed, coming up with a section restoration method. [Method] Firstly, the mechanism of intrusion limit in Yangtian Cave Tunnel of Tonglu County, Zhejiang Province, was analyzed from the aspects of lithology of surrounding rock and groundwater conditions;then, two methods of section restoration:the integral method and the ring-by-ring method, were proposed, which were analyzed and compared by means of the MIDAS-GTS finite element software. [Result] During construction in the ring-by-ring method, the new displacement of surrounding rock is small, the cumulative settlement value of tunnel vault is 6 mm, and the cumulative convergence value of BC horizontal lateral line is 5 mm;the plastic zone range is obviously reduced, compared with the integral method;the maximum stress value of the supporting structure is 16.80 MPa. Although the supporting structure bears fairly large stress, it is still in a safe state, which indicates that the supporting structure can play a stronger supporting effect;therefore, the ring-by-ring method is the optimal method for section restoration. [Conclusion] The research results can provide a reference for similar tunnel initial support intrusion limit projects.