Underground Hydropower Plants

Most of the hydropower plants developed in a mountainous topography consist different underground structures such as headrace tunnels, pressure tunnels and shafts, powerhouse caverns, tailrace, and access tunnels. Design of underground structures in a cost effective and optimum way is a challenge and demands step wise investigations on the engineering geological condition of the area where these structures will be located. Orientating, shaping, and sizing plays an important role for the overall stability of each structures regarding both hydraulic requirements and long-term stability viewpoint. This manuscript briefly discusses on development history of underground hydropower plants in Norway, discusses steps of engineering geological investigations, highlights potential stability problems an underground opening may experience and elaborates on the design aspects practiced