软弱地层的大断面双连拱隧道设计与施工方案优化研究

为研究一种新的连拱隧道施工方法---无中墙单洞法在软弱围岩地层中的可行性和适用性,依托平文高速土基冲连拱隧道工程,采用数值模拟方法在施工力学性能方面对无中墙单洞法和传统的三导洞法进行比选分析,并通过现场监控量测结果验证工法的可行性和安全性。研究结果表明: 1)在支护结构受力性能方面,由于无中墙单洞法临时支护结构较少,结构处理圆顺,能更有效地减少应力集中现象; 2)在结构设计方面,由于无中墙单洞法取消了中隔墙结构,使得施工难度降低; 3)在施工工法方面,采用三台阶法分别对先行、后行隧道进行单洞施工,增加了作业空间,提高了施工组织效率; 4)综合考虑施工力学与工期进度的影响可知,无中墙单洞法适用性较好,可为类似地层条件下双连拱隧道的设计和施工提供参考。

Optimization of Design and Construction Scheme for Large Cross-section Double-arch Tunnel in Soft Ground

In order to study the feasibility and applicability of a new tunneling method in soft surrounding rock,i. e. the single-hole method without mid-wall,the comparative analysis is made on construction mechanical properties of the single-tunnel method without mid-wall and the traditional three-pilot drift method by means of numerical simulation based on the Pingyuan-WenshanHigh-speed Tujichong double-arch tunnel. Meanwhile, the feasibility and safety of the construction method are verified by the statistical analysis of the field monitoring results. The results show that: (1) In terms of deformation control, the two method meet the requirements of safe construction both, but the three-pilot drift method is slightly superior to the single-tunnel method without mid-wall. (2)In terms of the bearing performance of the supporting structure, the stress concentration phenomenon can be effectively reduced by the single-tunnel method without mid-wall for its less temporary support structure adopted and smooth structure. (3) In terms of the structural design, the construction difficulty of the single-tunnel method without mid-wall is small than that of three-pilot drift method due to mid-wall cancel. (4) In terms of the construction method, the construction space is enlarged and the construction organization efficiency is improved by adopting three-bench method to construct two single tunnels. (5) Considering the influence of construction mechanics and construction schedule, the the single-tunnel method without mid-wall has a good applicability which can provide reference for the design and construction of double-arch tunnels under similar stratum conditions in the future.