Cofferdam Removal of the Second Powerhouse of Abbaspour Dam
M.Moradi (Manager Deputy JAHAD TOSSE MANABE AB Co.)
A.P.Ruhi (Technical Office Expert JAHAD TOSSE MANABE AB Co.)
Abstract
The second powerhouse of Abbaspour dam has been constructed with an installed
capacity of 1000 MW. Two conic shaped concrete cofferdams were constructed to
prevent water flowing into the powerhouse during construction period. Each
cofferdam had 20 rings. After the construction of the powerhouse was completed, two
sequential methods were finally used to remove the cofferdams: Demolishing by
dynamite explosion in each cofferdam ring, 60 holes were hollowed out. After
explosion the concrete was removed easily by hand tools. To control hurled materials
arising from explosion, a platform was built around the cofferdams and the platform
was cleaned by use of a tower crane.
Removing the cofferdam by using a barge, on which a beam is placed. When the
barge was rested on the cofferdam, the tanks were filled with water and the barge sank
blow the surface of the water. After that the beam fixed to the concrete ring by using
three jaws. The fixed concrete ring could easily be removed by only letting the water
out of the tanks. The barge rises now to a higher level and separates the ring from the
cofferdam. Finally a tugboat is used for taking the barge to the upstream of the
reservoir to unload the rings.