Geomechanical Challenges and Engineering Solutions for Tunnel Stability in the Himalayas: A Case Study Approach

Abstract

The Himalayan region, characterized by complex geological formations and high tectonic activity, presents significant challenges for tunnel construction. This paper examines geomechanical issues such as tunnel squeezing, stress-induced instability, and rock bursting, with a focus on hydropower and railway tunnel projects in Nepal and India. Case studies, including the Chameliya Hydroelectric Project, Parbati II Hydroelectric Project, Nilgirikhola Hydroelectric Project, and railway tunnels in the Garhwal Himalaya, highlight the impact of weak, schistose rock masses and extreme overburden pressures. Various engineering methodologies, including empirical, semianalytical, analytical, and numerical modeling approaches, are discussed to assess stress states and deformation behavior. The study underscores the need for adaptive excavation techniques, such as the New Austrian Tunneling Method (NATM) and rock mass classification systems, to ensure tunnel stability. By integrating probabilistic analysis and advanced support systems, this research contributes to optimizing underground construction strategies in geologically challenging terrains.

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