Effect of Blast Damage Zone on Slope Optimization: A Case Study of the Himalayan Highway Slope

The highways in the Himalayan region pass through critical topographical settings along with varying geological and geotechnical conditions. These highways are significant links for connecting people and resource supply to remote areas, in addition to their strategic nature, necessitating stable slopes along the highway. However, different types of rock failures are exposed and highly vulnerable due to unscientific blasting practices, resulting in uneven slope profiles and overhanging of rock blocks along these highways. Drilling and blasting create an Excavation Damage Zone (EDZ) in rock masses, which intensifies due to poor blasting practices. The strength properties of the rock mass in EDZ deteriorated due to stress relief and disturbance of the natural fabric of the rock mass. In such circumstances, slope geometry optimization with controlled blasting techniques is an economic approach to stabilize rock slopes. Therefore, in this study, stability analysis and slope optimization of a jointed rock slope along NH 5 have been carried out through the Finite Element Method, considering a layer of blast-induced damage zone. The EDZ was taken into account during the assessment of rock mass strength parameters by including the disturbance factor ‘D’ introduced in the Hoek and Brown failure criterion. The study results signify the EDZ effect on the safety factor of joint highway slopes, along with strain concentration and deformation patterns. The factor of safety is found to be more sensitive to slope angle than slope height, coupled with the EDZ layer. It can be an effective approach to reduce the failure risk along hilly highways.