In this study, based on the construction of a large-span triple-arch tunnel, the authors focus on the surrounding rock mass deformation characteristic, evolution process of rock mass load, and mechanical behaviors of tunnel linings. Numerical modelling is used for rock mass deformation analysis. The leading tunnel excavation would disturb the rock mass of the lagging tunnel and cause its pre-deformation. As the middle tunnel lagged behind the two side tunnels, it showed much larger pre-settlement than the side tunnels. The field monitoring method is used to obtain the rock mass pressure, contact pressure between the tunnel linings, and steel stresses inside the tunnel linings. At the initial phase, the rock mass pressure and contact pressure of the linings rapidly increased; then, the monitored pressures tended to be stable until the rock mass was disturbed by the following excavation steps. Most of the steel stresses within the tunnel linings were compressive stresses and considerably lower than the yield strength, which meant that the tunnel linings were in a safe working state. The middle tunnel excavation is the most significant part of the triple-arch tunneling. It caused a significant increase in the rock mass load of the side tunnels, particularly the lateral load on sidewalls. The secondary lining of side tunnels shared most of the new increased load caused by middle tunnel excavation. Therefore, the lateral load-bearing capacity of the triple-arch tunnel was suggested to be improved. The rock mass load was symmetrically distributed along the central axis, but there was considerable bias load on the top and bottom of the division walls between the middle and side tunnels, which meant that the bending resistance and anti-overturning capacity of the division walls should be strengthened. According to the mechanical responses of the tunnel, some engineering suggestions are proposed for large-span triple-arch tunnelling. The results of this study can provide references for the design and construction of large-span triple-arch tunnels.

在这项研究中，作者基于大跨度三拱隧道的建设，着重研究了围岩的变形特征，岩体荷载的演化过程以及隧道衬砌的力学特性。数值建模用于岩体变形分析。领先的隧道开挖会扰乱落后隧道的岩体并引起其预变形。由于中间隧道落后于两侧隧道，因此其预沉降要比侧面隧道大得多。现场监测方法用于获得岩体压力，隧道衬砌之间的接触压力以及隧道衬砌内部的钢应力。在初始阶段，衬砌的岩体压力和接触压力迅速增加。然后，在随后的开挖步骤扰动岩体之前，监测到的压力趋于稳定。隧道衬砌内的大部分钢应力均为压应力，远低于屈服强度，这意味着隧道衬砌处于安全工作状态。中隧道开挖是三连拱隧道最重要的部分。这导致侧隧道的岩体负荷，特别是侧壁的侧向负荷显着增加。侧隧道的二次衬砌分担了由中间隧道开挖引起的大部分新增加的荷载。因此，建议提高三连拱隧道的侧向承载能力。岩体载荷沿中心轴对称分布，但是，在中间隧道和侧隧道之间的分隔壁的顶部和底部都存在相当大的偏压载荷，这意味着应该增强分隔壁的抗弯性和抗倾覆能力。根据隧道的力学响应，针对大跨度三连拱隧道提出了一些工程建议。研究结果可为大跨度三连拱隧道的设计和施工提供参考。