<p>The challenge of instability in both natural and man-made slopes poses significant challenges for researchers and geotechnical experts alike. This instability is influenced by a variety of factors such as precipitation, rising groundwater levels, and increased stress conditions. This study delves into the investigation of shear strength parameters at chainages 4145 and 4050 along the Z-Morh tunnel approach road. The Z-Morh tunnel is located in Himalayan region on National Highway 1 which connects two Union Territories of India: Jammu and Kashmir, and Ladakh. Through various consolidated undrained triaxial and direct shear tests, the research aimed to identify variations in strength characteristics. Notably, the results revealed that direct shear testing overestimated cohesion and internal friction angle by 14.7% and 14.2%, respectively. Furthermore, the study evaluated the slope stability of the approach road, which was being constructed completely in cutting, using limit equilibrium-based software’s. Analysis of factors such as cutting angle, back slope inclination, nail inclination, nail length, and nail arrangement was conducted for both short-term and long-term stability at chainages 4145 and 4050. It was found that a cutting angle of 75° was economically optimal, with a higher FoS associated with decreased cutting angle and closer nail spacing. Chainage 4145 emerged as a critical point, necessitating reinforcement with soil nails to enhance slope stability. The results of this study address a practical problem. In addition to determining the suitable cutting angle, they provide a cost-effective technique to enhance slope stability in-situ.</p>