蛇紋岩の分布する日高山脈をトンネル群で貫く: 北海道横断自動車道　夕張～占冠間

摘要

北海道横断自動車道は，黒松内町を起点として小樽市，札幌市，千歳市，夕張市，帯広市近郊を経て根室市および網走市に至る694kmの高速道路である．このうち小樽～札幌～夕張問および占冠～本別・足寄間が既に開通しており，残る夕張～占冠問34.5kmの開通により，道央圏と道東圏を結ぶ高速道路ネットワークが概成される．夕張IC～占冠IC間は，北に標高1，668mの夕張岳を有する夕張山地，終点側に大雪山系山地，南を高峻な日高山脈に挟まれた山岳地帯を東西に貫いていることから，これら山脈の造山作用に伴って生じた地質や地形の影響を考慮してさまざまな対策をとっている．本稿では，この間の8つのトンネルの概要を説明するとともに，その中でとくに技術的難易度の高かった穂別トンネル（4,318m）と占冠トンネル（3,824m）の計画と実施工内容を報告する．%The Hokkaido Odan Expressway is 694 km long and stretches from Kuromatsunai to Nemuro and Abashiri passing through Otaru, Sapporo, Chitose, Yubari and the outskirts of Obihiro. The section from Otaru to Sapporo to Yubari and the section from Shimukappu to Honbetsu/Ashoro are already in operation and the expressway network that links the centre and the east of Hokkaido was almost completed with the opening ofrnthe remaining section between Yubari and Shimukappu.rnAs the section between Yubari and Shimukappu interchanges is surrounded by the Yubari mountains which includes Yubaridake (1,668 m above sea level) on the north, the Daisetsu mountains on the northeast and Hidaka Mountains on the south. The highway is passing through these mountains from east to west. Various tunnelling techniques were taken in consideration of geological features and geomorphology that occur due to orogenic movement of these mountains. This report gives an overview of 8 tunnels on this section as well as plans and construction details for two of these which were technically difficult in particular: Hobetsu Tunnel (4,318 m) and Shimukappu Tunnel (3,824 m).