Increasing the discharge capacity at the Höljes dam in Klarälven, Sweden

• The Höljes dam was constructed during 1959-62 and is one of Sweden’s largest embankment dams, with a height of 80 m. The dam is classified in the highest category with regard to dam break consequences. There are three spillways: one bottom outlet, one primary spillway and one log flume. Their discharge capacity at full reservoir level is 185 m3/s, 1290 m3/s and 120 m3/s, respectively. The function of the spillways at full discharge has however been questioned. Two issues are of particular concern: (i) The stilling basin at the end of the chute from the primary spillway was originally designed for a discharge of less than 900 m3/s, and is now in poor condition. One of the concerns is whether the walls of the stilling basin could collapse at high discharge, which could lead to accelerating erosion towards the dam toe. (ii) The discharge from the bottom outlet is conveyed via the old diversion tunnel, in which a hydraulic jump occurs. There is a risk that the diversion tunnel outlet may be inundated at the design flood. The free aeration for the hydraulic jump would then be cutoff, which could lead to large-scale air pulsations and dangerous shock pressures. The design flood has also been questioned and recent recalculations give a 20-30 % increase in the design flood. During 2008, different measures are evaluated for increasing the discharge capacity so as to safely pass a higher design flood. Initially, three alternatives will be analyzed through hydraulic model tests:

Ämnesord

TEKNIK OCH TEKNOLOGIER  -- Samhällsbyggnadsteknik (hsv//swe)

ENGINEERING AND TECHNOLOGY  -- Civil Engineering (hsv//eng)

Nyckelord

design flood

discharge

spillway

stilling basin

Publikations- och innehållstyp

ref (ämneskategori)

kon (ämneskategori)