ABSTRACT
The construction work for the Morioka to Hachinohe section of the Tohoku Shinkansen is proceeding smoothly with a completion time set at December 2002. In this section, there are twenty-one short and long tunnels. The second Itsukaichi tunnel is one of these tunnels. It is a relatively short tunnel of 1,175 m. The entrance to this tunnel is located directly under national road No. 4 where approx. 15,000 vehicles pass daily. The tunnel must be routed under a small earth covering of 2 m to 5 m thick.
The tunnel was excavated using the NATM method. In the portion where the tunnel intersects the road, an all ground fastening (AGF) method was used as a supplementary method.
As a result, the top end and the face were prevented from collapsing and the tunnel was excavated while keeping the sinking of the ground surface to a minimum without interfering with road traffic.
