ABSTRACT
This paper is a summary report on the state of progress of tunnelling at the fault-crush zone of the Sasagamine Tunnel. The Sasagamine Tunnel, which is the longest mountain tunnel of Kochi Expressway, has two traffic lanes. This tunnel has been constructed in the area of the Sanbagawa Metamorphic Belt, a famous belt which is located between the Median Tectonic Line and the Mikabu Tectonic Line in Japan. The characteristic of this geology is that the belt is composed mainly of muddy crystalline schists and countless crush zones with fault clay. The result of the measurement at the crush zone, the maximum value of the initial inner cross section displacement of the first day after the excavation, was over 30mm. The final value of the inner cross section displacement was over 100mm. The temporal invert on the heading bench was effective in the control of the inner cross section.
