Slope management criteria for Alishan Highway based on database of heavy rainfall-induced slope failures

In this paper, a study of slope failures along the Alishan Highway (locally, known as “Tai-18”) is carried out. An innovative empirical model is developed based on 15-year records of typhoon rainfall-induced slope failures. This model is intended for assessing the likelihood of slope failure along Tai-18 in the future. The rainfall data considered in the proposed model include the maximum hourly rainfall and the effective cumulative rainfall. The effective cumulative rainfall is defined at the point when the curve of cumulative rainfall goes from steep to flat. Then, a simple criterion is established for assessing the potential of slope failure and issuing warning and/or closure for Tai-18 during a future extreme rainfall. Slope failures during Typhoon Saola in 2012 and those in Japan demonstrate that the new empirical model is effective and applicable to other regions with similar rainfall conditions.