Analytical and Numerical Stability Analysis of Road Cut Slopes in Garhwal Himalaya, India

The rocks of the Himalayan terrain are highly deformed and distorted due to complex geological and tectonics setup. Failures of slopes are always reported along National Highway (NH)-7, in the Uttarakhand Himalayan region, which causes loss of lives, traffic blockage, and destruction of property and also deterioration of the environment gradually. The road cut slope stability analysis of five locations were carried out along NH-7, between Shivpuri to Kaudiyala in Uttarakhand, India. For that a rigorous field investigation was done to collect the geotechnical parameters of slopes and also the potential instability condition of cut slopes were monitored with real time. To know the characteristic of rock mass, the geotechnical data's were studied based on rock mass rating (RMR) and geological strength index (GSI). The kinematics of the blocky (good and fair) rock-mass shows in general wedge, toppling and planar type of failures for different rock slopes. The petrography of representative rock samples was also carried out to see the mineralogical variation in quartzite and phyllitic quartzite. The comparative analysis of different empirical methods for slope stability as slope mass rating (SMR), continuous slope mass rating (Co-SMR), and Chinese slope mass rating (CSMR) shows a decent correlation and revealed that slopes are mostly partially stable. Q(slope) stability has also been applied to reveal the stability problems and to find out stable slope angle for different slopes. Further to clarify the stability of these slopes, numerical models (LEM and FEM) were applied. The numerical result, (FoS) of different slopes revealed that slopes are stable, critically stable and unstable, with a good agreement between LEM and FEM models. The collective effort of slope stability analysis through analytical and numerical methods will give the better perception to find out the potential remedial measures and optimum slope design.