阿里山森林铁路为世界闻名的高山铁路之一，惟受2009年莫拉克台风重创，森林铁路60k+550~61k+450二万坪路段发生大规模崩塌，路基严重流失，致使铁路停驶至今。为使森林铁路早日复驶，并能永续经营，采用费用较高、工期较长的迂回隧道方式进行修复。本案例无任何道路可供通达，施工前须辟建高难度的施工便道，以供后续人员、材料、机具进出； 台风、豪雨期间，崩塌区落石及土石流不断，施工便道维护及人员避难不易； 洞口腹地狭窄、崩积层进洞困难及林地生态保护等施工特色与技术难题，更非原规划设计足以因应。经业主、监造及施工团队数次应变处理后，勉以通过，其经验与心得可供后续类似案例参考。

Mt. Alishan is one of the most wellknown mountain forest railway, but the railway communication between Sta. 60k+550~61k+450 of Erwanping section has being disrupted until now, due to the serious run off of roadbase induced by the tremendous landcollapse, which occurred during the Typhoon Morakot since 2009. For early traffic reopen and capable of sustainable management of forest railway, the more expensive and long duration construction method Bypass Tunneling has been adopted for its rehabilitation. Owing to the lack of any available connections, the high construction difficulty of access roads should be built first for the mobilization and subsequent supplying of construction materials , equipments and manpower etc., and also for the access roads maintenance and workers evacuation when subjected to the uninterrupted rockfall and debris flow during the typhoon and rainstorm season. In addition to the construction characteristics and technical problems in the narrow hinterland of tunnel entrances, difficulty in tunnel entrancing through colluvial deposits and ecology protection for forest area, the original countermeasues of planning and design are inadequate. Finally, the tunnel is cut through with an effort after the several emergency treatments executed under the negotiation between the owner, supervisor and construction teams, and hope that the construction experiences of the project be useful for the references to similar cases in application.