浅埋软弱地层中连拱隧道有无中导洞施工工法对比研究

Comparative Study on Central Drift Excavation Method and Single-tunnel Excavation Method Applied in Multi-arch Tunnel in Shallow-buried Soft Ground

为研究无中导洞连拱隧道施工工法在浅埋软弱地层中的适用性,运用有限元数值模拟方法对无中导洞工法和传统的中导洞工法进行对比研究,重点从隧道开挖引起的围岩变形、支护结构主应力以及围岩塑性区分布进行了对比分析。结果表明:(1)在围岩扰动变形方面,无中导洞工法引起的拱顶沉降和外侧边墙水平位移均较小,但在邻近中墙侧产生稍大的侧向变形;(2)在支护结构受力方面,因临时支护结构少且结构刚度过渡更加圆顺,无中导洞工法有利于抵抗偏压荷载和减少应力集中;(3)在围岩塑性区分布方面,无中导洞工法施工造成的围岩塑性区分布范围和径向深度均较小,主要在中墙底部及其邻近的两侧拱脚位置稍大于有中导洞工法;(4)综合施工过程力学行为和施工效率,无中导洞连拱隧道工法在浅埋软弱地层中具有较强的可行性和适用性。

To study the applicability of the single-tunnel excavation method in multi-arch tunnel in shallow-buried soft ground,the comparative analysis is made on the construction mechanical responses of the central drift excavation method and the single-tunnel excavation method by numerical simulation with finite element method.In which,the comparisons are focused on the tunnel excavation-induced deformation of surrounding rock,principal stress of supporting structure and plastic zone of surrounding rock.The calculated results reveal that:(1)In terms of the surrounding rock deformation,the settlement of the vaults of the sub-tunnels as well as the horizontal displacements of the outside side walls by adopting single-tunnel excavation method is less than that in the central drift excavation method,but larger lateral deformation occurs at the side near the central wall;(2)In terms of the supporting structure stress,the stress value and the stress concentration can be both effectively reduced with single-tunnel excavation method owing to its few temporary supporting structures and strong structural integrity with smooth stiffness transition;(3)In terms of the surrounding rock plastic zone,the distribution range and the radial depth caused by single-tunnel excavation method are smaller,but is slightly larger at the location of the bottom of the central wall and its adjacent sides;(4)In view of the mechanical behaviors and construction efficiency,the single-tunnel excavation method for multi-arch tunnel has strong feasibility and applicability in the shallow-buried soft ground.