ABSTRACT:

Hoek & Brown introduced the disturbance factor, "D," to their failure criteria in order to account for the critical effect of blast-induced damage zone in the assessment of the rock mass parameters. Considering the vital effect of blast damage extent on the surficial stability of jointed cut slopes, the present study examines the stability behavior of a jointed cut slope that had been excavated through rough blasting practice along NH-5 in dynamic Himalayan conditions in Himachal Pradesh, India. The effect of the blast damage zone on the stability behavior has been investigated through continuum-based Finite Element modeling. A parametric study has been done by assigning different damage factor ‘D’ to the damage zone of the rock slope. The results demonstrate the variability in safety factors of jointed cut-slopes in relation to the extent and degree of blast-induced rock mass damage of the disturbance zones.

INTRODUCTION

In recent decades, the demand for constructing road networks in remote mountainous areas has been steadily increasing. However, the construction of roads in inaccessible hilly areas poses many challenges, such as geological conditions, limited equipment access, and lack of technological advancements. Drilling and blasting methods (DBM) are typically the only suitable excavation techniques for such critical conditions, as they are flexible and economical in nature (Murthy & Dey 2003, Verma et al. 2015, Ghosh et al. 2022). However, the excavation of rock slopes using DBM creates blast-induced damage zones, which leads to deterioration of the physical and mechanical properties of the rock masses (Saiang & Nordlund 2009 and Verma et al. 2018). The stability of high rock slopes along the roads is a significant concern to be dealt by engineering geology specialist, especially when using DBM for excavation. The stability issue is justified by road blockage, loss of human life, and hindrance to communication and trade. Therefore, the estimation of the stability of rock-cut slopes, constructed using DBM, has major challenges in considering the Excavation Damage Zones (EDZ) in highway cut slopes. The rock slope is considered to be nonlinear due to its inconstant nature, caused by the occurrence of joints and their varied conditions, faults, other natural discontinuities and anisotropy. Nonlinear failure criteria are widely used for the assessment of rock mass strength proposed by Hoek & Brown (1980) and Hoek et al. (2002) and their applicability, and restrictions are discussed by Marions et al. (2005).

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