Landslide disaster and its prevention works in Shikoku region of Japan

Abstract This study introduces two examples of landslide countermeasures in Shikoku, Japan. The first case is a landslide that occurred in the Chichibu belt. This landslide was characterized by loose rock mass (past landslide mass) distributed at a maximum thickness of approximately 30m. As a result of comparing and examining the three types of construction methods as countermeasures against this landslide, it was judged that the countermeasure works combining the anchor works and the drainage boring works was the most appropriate. This landslide experienced the largest downpours since the completion of the countermeasures, but no landslide activity has been confirmed. The second case is a landslide that occurred in the Mikabu belt. This site was a place where fragile geology was distributed, but a cut at the lower end of the slope was implemented for road construction. After this cutting work, landslides occurred on the slope during heavy rain. Two landslides occurred step by step with the rainfall. As a result of a comparative study of the two countermeasures for this landslide, it was determined that the countermeasure that combined earth removal, anchoring and drainage boring was the most appropriate. The landslide activity was stopped after the countermeasure work was completed, and road construction was completed safely.