History of road construction with discontinuous analysis in Japan
ByT. Nakai, K. Hatakeyama & Y. Ohnishi
Pages 8

ABSTRACT: Just 15 years ago discontinuous analysis started being applied the design of road construction. The first application was the construction of slope protection for the North Kyoto Highway using key block analysis under the direction of Ohnishi. Nakai presented this actual case at the special workshop at ICADD-2 (1997) in Kyoto. Successively, design and construction using key block analysis and Discontinuous Deformation Analysis (DDA) were performed on the road construction site of the Otaki Dam under the direction of Shi. Here, we were able to apply the usefulness of discontinuous analysis to secure the stability of huge unstable rock blocks. As the work progressed, key block analysis which Ryu et al. was applied to tunnel excavation. The first work was Ritto Tunnel of the New Meishin Highway presented at ICADD-4 (2001). Key block analysis was continually proposed to predict rock fall and failure in a complex situation with new digital photogrammetry technology at the Suzuka Tunnel construction using the Tunnel Boring Machine (TBM) advanced construction method presented at ICADD-6 (2003). Recently, the Manifold Method (MM) was applied to real slope stability problems with tunnel excavation associated with slope cutting and old railway tunnels. The effect of new tunnel construction on the pre-existing old railway tunnels should be carefully evaluated. Miki et al. proposed applying MM to road design and construction to secure the stability of the upcoming tunneling work and excavation presented at ICADD-9 (2009). Following these examples from 15 years of experience in Japan, this paper reviews the history of road construction using discontinuous analysis in Japan and verifies its effectiveness in rock mass design.