ABSTRACT
The hydropower industry has unfortunately experienced several tunnel failures over recent years. The risks and challenges for the successful design and construction of hydropower tunnels are much more elevated in comparison to other types of tunnels as hydropower tunnels are subjected to dynamic operating conditions that are not always fully known prior to operation. Many hydropower tunnels have been designed and constructed as unlined tunnels incorporating shotcrete lining only in limited areas based on technical assessments performed during and at the later stages of construction. The technical assessment can however be subject to limited access, limited data collection from mapping, concealed instability of TBM excavated tunnels, and the misunderstanding of dynamic hydraulic operations. The main risks associated with the design and construction of hydropower tunnels along with causes of recent collapses are presented and explained along with suggestions for improved industry practice.
