Himalayan rock mass and possibility of limiting concrete lined pressure tunnel length in hydropower projects in the Himalaya: Fid-Bau Portal

Himalayan rock mass and possibility of limiting concrete lined pressure tunnel length in hydropower projects in the Himalaya

Panthi, Krishna Kanta

Abstract

In recent past, the development activity in hydropower sector got momentum in the Himalayan region. However, the investment cost is considered considerably higher than in other part of the world, and there is a strong need to look for alternative solutions that reduces the investment cost. Civil engineering part of the costs is one of the major areas where cost reductions could be made by involving today's construction technology. As it is well known, the use of underground space, such as waterway tunnels, shafts, and underground caverns, are inevitable in the development of hydropower projects in the Himalaya. Finding innovative solutions in underground construction is therefore a key issue where cost reductions can be achieved to improve financial viability. It is highlighted here that the traditionally used fully concrete lined waterway system has proven to be costly solutions; therefore, innovative solutions are needed to reduce the fully concrete lined length of the pressure tunnels. However, applied solutions must guarantee long-term stability and sustainability, cost-effectiveness, and construction time savings. This paper presents some design considerations that could be used to reduce fully concrete lined tunnel length for low to medium pressure waterway tunnels. Adoption of such an approach will help reduce overall construction costs and times. However, one should make sure that the prevailing rock mass conditions and applied tunnel rock support consisting of sprayed concrete and systematic bolting are enough to secure long-term stability and safety of the waterway system.