无导洞法双连拱隧道施工方案优化研究

Study on Optimization of Construction Scheme of Double-Arch Tunnel without Middle Drift

目前,传统的连拱隧道施工方法存在施工工序多、临时支护量大、对围岩扰动频繁等问题。为了避免上述问题,以宜金高速黄角坪隧道工程为依托,提出了两种无中导洞法施工方案,通过数值模拟建立地层结构模型,详细分析了不同方案施工过程中围岩的变形特性以及结构的受力特征。研究表明:后行洞开始掘进时,围岩位移和塑性区会明显增大,最终拱顶处形成一个“人字形”塌落拱;初期支护和二次衬砌上的最大压应力都是位于先行洞中墙墙脚位置;二次衬砌的最大拉应力主要位于拱顶内侧或仰拱内侧,而初期支护的最大拉应力很小影响不大;总体来看,方案一施工效率较高,方案二相对保守安全。研究成果可为今后无中导洞双连拱隧道的施工提供参考和借鉴。

At present,there exist some problems in the traditional double-arch tunnel construction method,such as complicated construction procedures,a large number of temporary supports and the effect of frequent disturbance on surrounding rock.In order to avoid the above problems,based on a double-arch tunnel project of Yijin freeway,this paper puts forward two construction schemes without middle drift,and then uses numerical simulation method to analyze the stability and deformation of surrounding rock and the mechanical characteristics of the structure in the different construction schemes.The results show that the displacement and plastic zone of surrounding rock will increase obviously when the second tunnel is excavated subsequently,and then a"herringbone"collapsing arch is formed above the crown of the second tunnel.The maximum compressive stress of the preliminary support and the secondary lining is located at the foot of the wall in the first tunnel.The maximum tensile stress of the secondary lining is mainly located at the inner side of the crown or invert,while the maximum tensile stress of the primary support is small.Overall,scheme 1 has higher construction efficiency,and scheme 2 is relatively conservative and safe.The research results have great significance for theory and practice,and also provide a reference for the construction of double-arch tunnel without middle drift in the future.