Use of a TBM on Nepal’s Sunkoshi Marin and Bheri Babai projects, in mountainous terrain

Tunnels play a key role in the Nepal’s hydropower and water resources development, and projects often need to be implemented in mountainous terrain. To date, the drill and blast method has generally been used, as there have been doubts about the use of TBMs in the challenging Himalayan context. Therefore, no real experience on mechanized tunnelling methods was gained until recently by developers. This paper examines the valuable lessons learned with the first successful use of TBMs for two Nepalese multipurpose hydro projects, and recommendations are drawn for future hydropower projects in similar conditions.