Investigation of the effect of road building on landslide occurrence using the FLAC SLOPE model (Case Study: Ilam dam watershed)

Landslides are one of the destructive erosion events in slopes that cause financial losses on the roads. Nowadays landslides are more influenced by human activities than natural aspect. But one of the important human activities in landslide event is road construction in most of Watersheds. In this research the effect of the road in landslide event in part of the Ilam dams, in southeast Ilam with 18360 hectare was evaluated by slope stability model (FLAC SLOP). After selecting the slopes, requirement parameters by soil sampling were done in each slope. To determine the factor of safety (FS), these parameters were considered as the input in the model and FS values were calculated. In the next step effect of road on selected slopes was applied in the model. The results indicated that the road building in slopes with more than 15 percent steepness decreased the stability of slopes. Also using this model could help recognize unstable slopes and could characterize conservation operations to increase slop stability. Based on results operations like nailing and terraces increase slope stability up to 20 percent.