ABSTRACT
The Minoh toll road mountain tunneling project (southern lot) includes construction of a main tunnel (2000 meters long), an evacuation tunnel (2009 meters long), a working tunnel (354 meters long) and crosscuts. The south entrance of the main tunnel, which connects with the on-off ramps, has an extremely large section exceeding 300 square meters at maximum. The geology is Osaka stratum group over 100 meters from the south entrance, and Tamba zone in the rest. Actually, the working tunnel construction has been completed, and parts of the main tunnel have been completed including about 500 meters to the north from the working tunnel, and about 150 meters to the south (as of January 2001). Since the geology is complex, the face was extremely unstable during excavation of the working tunnel with a significant volume of water inflow in many places.
This paper evaluates various auxiliary methods used in the working tunnel construction, focusing upon the effect of new injected long face reinforcement, and presents the design principle of this technique.
