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The paper describes the recent devastating landslide of Kotrupi, Himachal Pradesh in India which had claimed many human lives and properties along its course on 13 August 2017. This event was the third reactivation of the slide as per data available. The study for this landslide involves a preliminary investigation of the site and comparison of pre- and post-event slope stability analysis. Other than rainfall, the combined effect of differential weathering rate of the debris and soil layers, low material strength, and the presence of a fault zone was found to be the primary cause of instability. The analysis was carried out with the geotechnical investigation and numerical modeling with the help of finite element model-based Phase 2 simulator. The significant findings of this paper include numerical simulation of pre- and post-event slide as stated under unsaturated and saturated condition. The study finds a low factor of safety of the present slope. The unstable condition of the slope may trigger another event of the same intensity shortly. [ABSTRACT FROM AUTHOR]

This study investigates the role of bed-material anisotropy in triggering landslides in metamorphic terrains of the Darjeeling-Sikkim Himalaya. The initial disposition of foliation (planar anisotropy) with respect to the hillslopes is found to be a crucial parameter in controlling the scale of landslides. Hillslopes with foliation dipping into the surface slope are mostly affected by deeper-seated larger-scale landslides, as compared with those occurring on hills with down slope-dipping foliations. To verify our field observations, we performed scaled slope-failure experiments in a tilted sandbox, simulating the foliation anisotropy in analogue models. Sand-mica beds with the anisotropy planes dipping into the surface slope developed shear localisation along deep-penetrating listric zones, leading to slope failure in the form of down-sliding blocks of large dimensions. In contrast, models with anisotropic planes dipping down slope produced failure zones restricted to the shallow level. The narrow failure zones in the latter case had little tendency to grow in depth but propagated up the hillslope direction. Using Drucker-Prager's failure criterion, we also ran experiments with finite element models to substantiate the contrasting effects of bed anisotropy on hillslope failure processes. [ABSTRACT FROM AUTHOR]