Abstract
Although there has been an increase in the number of slope disasters occurring along roads every year, there have been reports of slope disasters occurring in many places along roads that were judged as safe as a result of preventive measures carried out in 1996, 2001, and 2006. Further, considering the recent increase in the amount of local rainfall, it has become crucial to assess the risk of slope failure by taking into account the effects of rainfall on slope failure. In this study, our objective is to assess the risk of slope failure by taking into account rainfall characteristics and each slope feature along expressways. We attempt to achieve this by using a qualification theory. The factors contributing to slope failure are determined for every cut slope and natural slope. Then, on the basis of heavy rainfall data of 2004, the Soil Water Index for grids of 2.5 km each are calculated. The contributing factors and the Soil Water Index are analyzed by using a qualification theory, and the areas at risk of slope failure are determined. As a result of this approach, i.e., the classification accuracy to extract the unstable slops in natural slopes has risen compared with classification accuracy by using only slope features.
