POWER, WATER & STORAGE | SECTOR
USING TBMS IN HIMALAYAN HYDRO
Use and applicability of TBMs for constructing headrace tunnels in Himalayan hydropower projects is discussed by consultant Dean Brox.
ABSTRACT: Tunnel boring machines (TBMs) have been used for the construction of long tunnels for more than 70 years and their use has included a number of long tunnels for hydropower and other civil infrastructure projects. Most of the major mountain ranges – including
the Alps, Andes, Caucasus, Himalayas, and Rockies, where several hydropower projects have been built and continue to be planned – are associated with high overburden and challenging geotechnical conditions for the construction of long tunnels. The historical use of TBMs in the Himalayas was hampered with challenges, some due to specific aspects not directly related to geotechnical risks but rather the inappropriate type of TBM for the prevailing geological conditions. Two TBM-driven tunnels for hydropower/multi-
purpose water projects have been recently completely successfully, and ahead of schedule, in Nepal, with progress rates of more than 20m/day; this has spurned renewed interest in their use for future projects. Two TBMs also successfully completed 20km of the central section of the 28.5km-long headrace tunnel – also the deepest tunnel in the Himalayas – at the Neelum Jhelum project, in Pakistan. TBMs are also in current use on two major hydro projects in India that have indicated positive progress to date with up to 43m of advance in a single day.
Past, recent, and present projects for TBMs for
hydro projects in the Himalayas are presented and discussed, along with the key risks and logistical challenges, and the technical evaluations necessary in early studies.
1 INTRODUCTION TBMs have been used in construction of long tunnels, including for hydropower and civil infrastructure projects, respectively, for decades. In most major mountain ranges these long tunnel projects have high overburden and are excavated in challenging geotechnical conditions. Goel (2014, 2016) presented several challenges and
lessons learned associated with the first series of TBMs that were attempted to be used in the Himalayas from the late 1980’s to the late 2000’s. Given that there have been some very positive results within the past decade and in particular, most recently with some ongoing projects, it is warranted to document a fresh perspective for the use and applicability of TBMs in the Himalayas. With improved technical evaluations and risk
management practices having provided success, the tendency in the past to shy away from application of TBMs in major mountains due to actual problems encountered, and/or perceived risks, should now be challenged.
Above, figure 1: Prominent dipping bedrock geology in the Himalayas PHOTO: MILLEN, B. & BRANDL, J (2011) October 2025 | 19
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