Abstract
Full-face tunnel excavation has been increasingly employed for SEM (sequential excavated method) tunneling by the virtue of enhanced capacity of roadheaders as well as the ground control effect of early ring closure. As the stability of the tunnel face is essential to full-face tunnel excavation, the tunnel stabilizing method utilizing curved tunnel faces, which would naturally form as part of the tunnel excavation sequences, can be considered effective. This paper addresses an investigation into the characteristics of the shape of curved tunnel face employing numerical models, and the stabilizing effect of tunnel face reinforcing methods, such as shotcrete on tunnel face, using physical models. Further, the constructability and stability of curved tunnel face were verified through trial excavations at an actual tunneling site. As a result it is confirmed that curved tunnel faces are advantageous and the stability of the tunnel face can be improved by a simple reinforcing method such as shotcrete on tunnel face. The trial excavations undertaken have proved the favorable constructability and stability of curved tunnel face. In addition, a conceptual approach to selection of the shape of curve tunnel face and its stabilization behavior is suggested together with a concept of tunnel face stabilizing method proposed.
