Stability evaluation of discontinuous rock slope

In Japan, the evaluations of many dangerous discontinuous rock slopes have been urgently carried out from view-points of geography, geology, slope conditions and the risky aspects of present slope location, etc, in each local region since Toyohama Tunnel in Hokkaido largely failed in 1996 and consequently a number of passengers suddenly died. However this evaluation method is not now perfect, because the contents of it cannot clearly determine both the influence zone and the degree of rock block falling on the road nearby the toe of dangerous rock slope. The purpose of this paper is to propose an original procedure for drawing up a road hazard map along the toe of dangerous rock slopes. The map will be based on the analyses for both the possibility and the extended length of each rock block falling from the Distinct Element Method with taking the Image Processing Method into consideration.