Enhancing tunnel stability in the Himalayas: Empirical design support through numerical modelling

Abstract

This study focuses on assessing the effectiveness of an empirically recommended support design through numerical modelling. Numerical techniques are utilized to accurately evaluate tunnel stability under various geological conditions. Numerical analysis is conducted on two different rock types along the tunnel route, employing the recommended support design based on the existing rock mass rating (RMR) and Q‐system. Furthermore, support recommendations are made using the modified RMR and Q‐system, considering the impact of stress. The numerical analysis indicates that the support recommended by the existing RMR may not substantially impact the total displacement and vertical stresses around the tunnel crown in the “Fair” to “Poor” rock mass of the study area. However, extending the bolt length by modifying the RMR to incorporate stress effects results in a reduction of total displacement and vertical stresses, ultimately achieving a stable level. These results underline the importance of considering stress effects and utilizing modified support designs to enhance tunnel stability.