Study of the triggering mechanism for rainfall-induced reactivated landslide occurred in a gentle slope Available to Purchase

A small-scale landslide occurred in Butterfly Valley in 2011. However, the treatment measures at that time were not targeted due to a lack of understanding of the sliding mechanisms, resulting in the blockage of some drainage points. In June 2015, the Butterfly Valley slope slid again after heavy rainfall, resulting in severe deformation. The scope and scale of the landslide were more extensive than those in 2011, and some roads were severely damaged, which brought safety risks to this scenic area. The field investigation results and the monitoring data showed that the stratum of the Butterfly Valley was characterised by a typical binary stratigraphic structure composed of clay on the surface and highly weathered rocks underlying it. Using the Geo-Slope simulation software, it was found that the primary cause of the landslide reactivation was the rise in groundwater level under this stratigraphic structure. This rise increased the uplift pressure from confined water and decreased the strength of the clay layer above the highly weathered basalt. Meanwhile, the equation for the factor of safety was modified using the Janbu method and the stability of the Butterfly Valley landslide was discussed. This study contributes to the safety evaluation and prevention of similar landslides on gentle slopes.