Stability evaluation of road-cut slopes in the Lesser Himalaya of Uttarakhand, India: conventional and numerical approaches

The hilly terrains of Himalaya are among the most vulnerable of the regions of India due to natural hazards. Different kinds of landslides occur frequently in the tectonically and geodynamically active region of Himalaya. Transportation, public networks, and all kinds of socioeconomic activities that occur in the high hills of the Lesser Himalaya are entirely dependent upon the local road and highway network in this region. However, the stability of the slopes that have been cut to construct and/or widen roads and highways is a major concern in hilly regions. Unplanned excavations performed by blasting have resulted in these cut slopes that are on the verge of instability. Such slopes become vulnerable under the influence of factors such as heavy rainfall, seismic activity, dynamic loading, and/or various kinds of human intervention. Any kind of slope failure can lead to disruption of traffic, losses of property and lives, injuries, as well as environmental degradation. In the present study, a slope stability analysis was performed of road-cut slopes along about 20 km of NH-109 from Rudraprayag to Agastmuni in the state of Uttarakhand in India. Based on field observations and variations in geological and geotechnical conditions, five locations were chosen for detailed study, including a laboratory study and numerical analysis. The two-dimensional conventional limit equilibrium method and a numerical technique based on the finite element method were used to analyze the cut slopes. This comparative analysis of slope stability provided a deeper understanding of this issue. The results of the analyses performed using both methods aided in identifying potentially vulnerable slopes and enabled us to compare the two methods.