Field, experimental and numerical study for landslide mitigation in Himachal Pradesh, India: Case study

Landslides frequently disrupt road networks in the mountainous region of Himachal Pradesh, India causing traffic delays and disconnecting the supplies of essential commodities within the affected regions. Therefore, it is essential to establish a comprehensive investigation mechanism to identify the triggering factors and develop effective mitigation strategies through well-defined design protocols. This paper presents a detailed investigation on a shallow landslide that destroyed newly built bridge and blocked rural road connectivity of 14 villages to Mandi town of Himachal Pradesh, India on 14th August 2020. We analyzed geophysical, geotechnical, geological and hydrological data to better understand the characteristics of the landslide. This provided the basis of suggesting suitable mitigation measures based on two-dimensional finite element-based numerical modelling. The results obtained revealed that the anthropogenic activity was the primary cause of the landslide with excessive rainfall acted as the triggering factor. Weak layers and discontinuities in the slope materials and soil conditions increased the landslide risk. The results of numerical modelling suggested that the slope had low safety factors under saturated conditions indicating the importance of water table location in changing the effective stress regime within the soil. Mitigation measures were proposed that included grouted soil nails indicating the factor of safety more than 1 for all the possible loading scenario. The findings of this study provide a comprehensive understanding of landslide characteristics and necessary procedure for mitigating slopes in the Himalayan region. The study can assist in developing effective strategies to reduce the occurrence and impact of landslides in the region.