January 25: A tunnel construction site
by Mie

The other day, my husband "explored" a tunnel construction site not-so-far from home. It sounds me unusual and we soon headed to the site with a digital camera in hand. We passed a crossing on which a traffic sign shows the routes to central Oita (left) and Taketa City (right.)

After Tajiri New Town, we turned south to go upstream of Tajiri stream that winds up to Kamishirakawa village in the foot of Ryouzen hill. I found many billboards like those on the road after seeing off a trail to the village. (Left) The sign reads "Dead end ahead." (Right) They read: from left, "Large-sized vehicles' waiting zone", "Blasting siren pattern", "Off limit", and "Thank you for your attention." They gave me a tension.

The overall view of the site, looking from the front base. The orange arrow indicates the entrance of the tunnel. The soil excavated from the tunnel is dumped onto the sunken place and will be finally converted to rice paddies. The roads will lead us to Ohno town in Ohno county in the end. A dangerous winding trail in the mountains will be widened and made straight by making tunnels like this.

Mr. Nobuyuki Kato, a safety supervisor, kindly brought us helmets and guided us into the tunnel under construction. He first saw my digital camera, then spoke about the Internet. What is surprising, he is a friend of Miss Korenaga, a COARA office member! How small the world is ! All of us were delighted and laughed.

At the entrance of the tunnel is a large machine called "Slide-central." It is moves on the rail by moters to make a semicircular frame for concrete lining work inside of the tunnel.

What is the most dangerous in a tunnel construction work is water break , he explains me. Luckily, the nature of the underground in the tunnel was dry, yet there are some anti-water measures such as vinyl covers and drain pipes.

Many long bolts are inserted to radial direction all through the tunnel length. Since the both ends of the tunnel are weak, they are reinforced with semicircular steel beams. Mr. Kato points out a part of the beam visible at the surface of the wall. The beam will become the base of further frame works to make floor, side wall, and ceiling. He elaborately explained us in a very easy way.

I walked through the 143-meter long tunnel. The construction was hard in its own way because it is slightly curved and has an up-incline of seven degrees, he said.

"I passed under the tunnel to find the world outside covered with snow...", Yasunari Kawabata, a Japanese Nobel prize winner for literature wrote. I stand on the edge of a precipice instead. There is no road yet. Even Mr. Kato doesn't know whether a bridge or a road will extend beyond the edge.

I found a good item. The sign reads "Congratulations the penetration, Kami-Ishikawa Tunnel." The ceremony was held on last Christmas day. It took two months to complete the tunnel after the first probe penetrated the last chunk of rock. (Right) The edge of the "road" (right) and a remnant of old trail (above.)

Thank you very much Mr. Kato, we appreciate your kindness of sharing busy time for us. We will return now. Naked bulbs hung down from the ceiling of the roughly-dug tunnel and a wonderful silhouette of the Slide Controller is visible ahead, creating a something wonderful illusion.

The explanation boards illustrate the anatomy of the construction, showing the inclination of the tunnel (left) and the cross-section (right) with many bolts piled deeply (four-meter long) into the rocky soil of the mountain.

Workers came back the rest-house for lunch. Most of them are the residents of Oita, but some people came from Kumamoto and Nagasaki who stay at a construction lodgings nearby. The construction will last one year or so. There has been no accident until today. I wish they will work safely all through the project.

I found a billboard like this, reading "Your gas-tax and car-weight-tax are exclusively used for road construction." I wish the road will complete someday down to Ohno town and further to make the traffic easier.

Thank you very much.

Mie Home