The Lesser Himalayan regions face significant geotechnical challenges due to unstable and erosive soil. This study investigates stabilizing these soils with Nano-silica (NS), a reliant additive that has been demonstrated to enhance soil mechanical properties. A comprehensive set of investigations, including multiple laboratory analyses, was conducted to evaluate the mechanical and physical characteristics of problematic soil stabilized with NS. The study also includes reliability analysis to assess the long-term performance and durability of the treated soil. The results of the experiment showed that adding NS greatly increased the soil's compressibility. More precisely, the right amount of NS increased the strength of the problematic soil and resulted in a notable rise in compressibility. According to the durability test results, stabilizing problematic soil with NS and allowing it to cure preserves its improved properties for an extended length of time. Reliability research utilizing probabilistic methodologies showed that applying NS considerably decreased the likelihood of problematic soil failure. The findings show that NS has the potential to be a stable, troublesome soil stabilizer that can lower the probability of soil failure in the Lesser Himalayan regions over the long run. This work provides a foundational understanding for future applications and paves the way for the construction of more robust infrastructure in mountainous terrain.