HIGOKITA ROAD TUNNEL BLASTS THROUGH DIFFICULT TERRAIN.

The 6 km-long Higokita Tunnel is to be an essential link on the new Kyushu Highway. With 23 tunnels totalling over 18 km in length on the new highway between Yatsushiro and Hitoyoshi, the 6 km-long twin tube Higokita Tunnel is a good example of Japanese drill and blast technique now in use on a vast scale for road tunnelling. The Higokita Tunnels are being driven from both ends by different joint ventures. From the north, a jv of Taisei Construction and Tekken Kensetsu KK is doing about 3 km of the work, and from the south a joint venture of Kasima Construction and Hazama Gumi KK is doing another 3 km. This article discusses various aspects of the project, including route geology, drilling equipment, ground support, and others.