It has been decided that the entrance to the Tsushima Aren Incline Shaft will be constructed using the liner plate method, and work is progressing smoothly. The liner plate method is a construction method in which the lower half is made of reinforced concrete, and the upper half is made of H-beams assembled into an arch shape and solidified with concrete. Once completed, the entrance to the tunnel will be 6m in diameter, 5.2m long, and will slope down 1m every 4m.
The construction method and location of the tunnel entrance were finally decided in early June, and work began immediately. It was decided that the best way to locate it was to jut out about 2m from the tunnel slope, and backfill the surrounding area with soil to blend in with the mountain. The tip of the excavator was fitted with a rock-breaking device called a "breaker," which was pounded into the huge, hard bedrock, breaking it down into smaller pieces. The crushed earth and sand was then transported away in dump trucks to widen the surface of the tunnel entrance. "As we expected, the bedrock was hard, so it took a long time," said the site supervisor.
Although it is the rainy season, there has been little rain and work is progressing smoothly. Starting on June 14th, the floor was prepared with a 1/4 downward slope, and after the concrete was poured, rebar was installed and the formwork for pouring the concrete was assembled over two days. It is 3m high. On the 20th, ready-mixed concrete was poured into the formwork for the left and right side walls. We are currently waiting for the concrete to dry.
The formwork will be removed on June 30th, revealing the lower half of the mine entrance. After backfilling with soil and soil improvement work on the soft ground layer, the upper half of the materials will be delivered in mid-July, and if all goes well, the mine entrance is scheduled to be completed by the end of the month.
The Tsushima Arirang Festival, one of Tsushima's summer festivals, which has been held on the first Saturday and Sunday of August, was canceled last year due to a Buddhist statue issue, but is set to resume this year. The hot festival season is upon us.
International Highway Foundation Newsletter July 2014 (PDF view/download)
