Underground hydroelectric power station Kárahjúkar II., Iceland


Landsvirkjun (National Power Company), Iceland

Superior Contractor

IMPREGILO S.p.A. Iceland Branch

Construction period

March 2005 – June 2006

Objects description:

  • company executed excavation works at construction of feeders from dam to the underground hydroelectric power station Kárahjúkar

Construction technology:
Tunnels were excavated by using drilling and blasting works, by NMT – (Norwegian Tunnelling Method). Drilling works were carried out by drilling jumbo Tamrock Axera T 11, T 08 with extended feeds that allowed to drill up to advance lenght 5 m long shots. Putzmeister WKM 133 was used for stabilizing by shotcrete. Loading in the tunnel was performed by wheel loader CAT 966 with side tipping. Mucking from tunnel was executed by dumpers Paus, trail sets and conveyor belt system.

Executed works:

  • surge tunnel in front of water inflow into vertical shafts to powerhouse, length 1 680 m, profile 18,3 – 23 m2
  • main headrace tunnel from dam to powerhouse, length 1 600 m, profile 56 m2
  • shaft for power intake gate, depth 90 m, profile 64 m2
  • primary support was realized by shotcrete reinforced with steel fibers and SN anchors