Assessment and Numerical Analysis of Hydropower Tunnel in Lesser Himalayan Region of Nepal- a Case Study

This paper is focused on the assessment and numerical analysis of hydropower tunnel of the Lesser Himalayan Region of Nepal. This region lies between two major faults namely Main Boundary Thrust (MBT) and the Main Central Thrust (MCT) with weak rock mass like phyllite, schist, gneiss, phyllitic schist, etc. Thus, to overcome the stability problems during underground construction, proper rock support system must be installed. Rock mass classification systems are commonly used for estimating the rock support system in this region, but this approach is inadequate to address the underground stability problems. In this study, numerical analysis is done to define the requirement of support and the result compared to actual support provided in selected case study. Analytical approach is used along with two-dimensional Finite Element Analysis using the software, RS² provided by RocScience for the study. Finally, required modification of the provided support has been suggested to overcome the problem faced in the selected tunnel.