Situated 130m deep inside the hill south of the
Palmwash, the Powerhouse Complex consists of three long caverns, parallel
to each other with appurtenant trenches and recesses and their
interconnecting galleries. The largest of the three caverns is the Machine
cavern with the ability to house four 80 MW generators with their turbines
housed in the central part. At the western and eastern end respectively
are a large four-story Control Building and the Workshop Area. The cavern
is 141.5m long, 16m wide and 36.5m high and is connected to the outside by
a 360m long access gallery for vehicle transit.
Some 75 000m³ of concrete has been applied
underground, mainly for the encasement of draft tubes and turbines - part
in the tunnels and shafts and part in the Powerhouse Complex. The concrete
was transported by truck mixers. Plain, mild and high intensity steel was
used - a total of 3 500 tons. Temperature control was performed to ensure
that fresh concrete, when placed in the final position did not exceed 25ºC.
Shotcrete was made for underground permanent lining and used for the
access gallery, the roof of the tailrace tunnel, the roofs of the machine
hall and surge chamber as well as the roofs and halls of the transformer
hall. A total of 3 700m³ underground shotcrete was mainly supported by
2.88 and 7.7 kg/m² of steel fabric. Additives were adapted for faster
setting and hardening of the shotcrete.
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