Traditional methods and ICT

The Onuma Tunnel is located between the Nanae Interchange (tentative name) and the Onuma Koen Interchange on the Trans-Hokkaido Expressway. The evacuation tunnel is currently under construction. The main tunnel is scheduled to become the longest road tunnel in Hokkaido when it opens (as of 2020).

The NATM (New Austrian Tunneling Method) used in the construction of this evacuation tunnel is for excavating a mountain, spraying concrete to form the tunnel and placing rock bolts to secure the concrete and rock to hold the tunnel in place, utilizing the bearing capacity of the ground.
NATM is a common method, but on this project the excavated soil (muck) was transported out of the tunnel by rail, a method rarely used in modern times. This was chosen because of the small cross-section of the tunnel which is only 4.26 m wide and 3.60 m high. The working space is too narrow for dump trucks, so rails are laid inside the tunnel and the soil is transported out in muck cars by special locomotives.

Of the seven tunnel construction projects I have been involved in over the past 20 years, this is the first time this method was used. Road haulage using dump trucks and other vehicles is currently most common, but there are some sites, such as this evacuation tunnel, where rail haulage must be used. For the workers including me, this is a valuable experience.
In addition to this rare technique, the project also incorporates new technologies such as CIM, a system that integrates all aspects of survey, planning, design, construction, and maintenance management into a 3D model, and “direct,” a high-security business chat tool with intuitive operability. In this sense, this construction site exemplifies Obayashi's comprehensive technologies.

Neighborhood safety

Understanding from the local residents is essential for us to construct the evacuation tunnel. We publish a monthly newsletter to explain situations such as the management of the excavated soil, the schedule and the progress of the construction and post it at the local community center and distribute it to each household.

In the newsletter, we convey important safety information using various photos of the site. Information related to areas outside the construction site, like the schedule and haul routes of large vehicle traffic, is especially welcomed by the residents.

Toward the completion

Despite the natural disasters like a big typhoon and the 2018 Hokkaido Eastern Iburi earthquake, the construction work has progressed smoothly. I believe that this is due to the efforts of each and every person involved in the construction of the Onuma Tunnel. For the workers from different companies to maximize their abilities at the site, communication is indispensable. I keep reminding myself that this work is impossible without people, and I endeavor to interact with integrity to all personnel, clients, local community members and all other project stakeholders.

The construction of the Onuma Tunnel is sure to leave its mark on tunnel history. I am looking forward to the day of its completion ceremony when I can breathe a big sigh of relief.