大規模な破碎帯と熱水変質地山における双設道路トンネルの施工: 新名神高速道路 野登トンネル

摘要

The Nonobori Tunnel is a two-lane road tunnel of 4.1km in length located between Komono IC and Kameyama-Nishi Junction on the Shin-Meishin Expressway. Emergence of fractured zone and welling water during excavation was estimated from the planning phase of the Nonobori Tunnel East works, but it was ascertained that a large-scale fractured zone with marked deformation and hydrothermal alteration zone existed by a result of excavation. Consequently, as well as adopting effective drainage, selecting auxiliary methods based on observation and measurement data and selecting suitable tunnel support for the ground brought about completion of excavation without problem. In addition, the necessity of a distance of 5D (around 50m) between the twin tunnels was verified in concerned section in order to neutralize the reciprocal effects involved in approximation of cutting faces of the twin tunnels.%野登トンネルは，新名神高速道路の菰野IC～亀山西JCT間に位置する延長4.1kmの2車線道路トンネルである.野登トンネル東工事では，当初から，破砕带区間と突発湧水の出現が想定されていたが，掘削の結果著しい変形を伴う大規模な破砕帯と熱水変質地山が存在することが判明した.そこで，効果的な水抜き工法の採用に加え，観察や計測データにもとづいた補助工法と地山に適合した支保パターンを選定することで掘削を無事完了させた.また，当該区間においては，双設トンネルの切羽接近に伴う相互影響をなくすためには，5D(50m程度)の離れが必要であることを検証した.