Design and Construction of InJe Tunnel, the Longest Road Tunnel of Korea

Abstract

Inje Tunnel, an 11 km-long twin-tunnel will be the longest road tunnel of Korea. Two parallel tunnels including two vertical shafts and one inclined shaft are under construction. Details of the tunnel design including geotechnical characteristics, cross-section of the excavation, reinforcement, drainage, ventilation operation, safety facility corresponding with a tunnel fire, and portal planning are introduced. Various analyses that systematically make comprehensive utilization of available data obtained from geotechnical investigations were applied for the optimal evaluation of ground conditions. The typical NATM excavation scheme by a combination of drilling, blasting and reinforcement has been undertaken. Steel-fiber mixed shotcrete, steel rib with Lattice girder, and rock bolt were designed for the reinforcement. Ventilation plan using the inclined shaft and vertical shafts are summarized considering traffic conditions and emergency situations. Current construction procedures are also briefly described.