ABSTRACT

In the paper, the authors propose a new quantitative assessment method of rock condition based on observational classification obtained at the tunnel face, which will enable to know either strength or deformability of rock mass, further more appropriate amount of rock bolts, thickness of shotcrete and size and pitch of steel ribs just after the blasting procedure. The study is confirmed by the database of up to the 6,101 sections of tunnels constructed by Japan Highway Public Corporation.