对于单向掘进的隧道，安全出洞是隧道顺利贯通的关键工序。文章以厦门金榜连拱隧道下穿挡墙段出洞为例，结合出洞口的地质条件和环境条件，对隧道出洞方案进行优化，并根据出洞施工监测数据，对施工中围岩和挡墙的变形进行了分析。研究结果表明：（1）将原37 m明挖出洞方案优化为靠山体一侧10 m暗挖、其余27 m洞顶加盖暗挖的方案，保留了原有挡墙和山体，降低了隧道施工噪音、粉尘等污染对周边居民生活的影响，节省了工期，使隧道出洞做到了安全、环保施工；（2）隧道出洞27 m洞顶加盖暗挖施工具有降低施工污染和兼作二次衬砌外侧模板的作用；（3）受外凸挡墙和山体的影响，左洞洞周收敛和拱顶沉降都是最大的，由于施作了两侧双排ϕ159钢管注浆围护桩，洞顶加盖暗挖段各洞洞周收敛均较小，收敛值在15 mm之内；（4）隧道施工过程中，整个挡墙及其所保护的山体基本上是向没有外力约束的临空面移动，而该方向正是隧道施工扰动的方向。%Considering that safe construction of the tunnel exit portal section is of great importance to the success⁃ful breakthrough of a unidirectional driven tunnel, and using the exit portal section of the Jinbang double-arch tun⁃nel in Xiamen, which passes under a retaining wall, as an example, scheme optimization is conducted based on the geological and environmental conditions at the tunnel exit portal, and the deformation of the surrounding rock and re⁃taining wall during construction are analyzed based on the measured data. The results show that: 1) after an opti⁃mized construction scheme (i.e., a 10-meter bored section on the side close to the mountain+a 27-meter bored sec⁃tion with roofing) was adopted instead of the original 37-meter open-cut construction scheme, the retaining wall and adjacent mountains were reserved, the impacts of construction noise and dust on the nearby residents were reduced, the construction period was shortened, and construction safety and environmental protection were ensured;2) in ad⁃dition to pollution reduction, the roofing of the 27-meter bored section also served as an extrados formwork of the secondary lining;3) subjected to the convex retaining wall and adjacent mountains, the left tube has both the maxi⁃mum convergence around the tunnel and the maximum vault settlement, and the convergence at the 27-meter bored section is relatively smaller with a value keeping within 15mm, which is attributed to the construction of two rows ofϕ159 steel pipe grouting piles on both sides;4) the retaining wall and adjacent protected mountains would move in the direction of the free face without any external-force constraint, and this direction is the one in which construc⁃tion disturbances occur.
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