Headrace tunnel for powerstation Kárahnjúkar, Iceland
Construction of headrace tunnel from dam to hydroelectric powerstation
Client: Landsvirkjun (the National Power Company)
Superior Contractor: IMPREGILO S. p. a. Iceland Branch
Structures description and completed works:
Project: Kárahnjúkar Hydroelectrical Project KAR 14.
Company executed excavation works at construction of feeding corridors from dam to underground hydroelectric powerstation Kárahnjúkar.
Completed structures:
- Surge tunnel with 18.3 to 23 sqm cross-section and 1 680 m length, it represents relieving weir tunnel in front of water inflow into vertical shafts to hydroelectric powerstation,
- main headrace tunnel from dam to hydroelectric powerstation with 56 sqm cross-section and 1 600 m length,
- gate shaft with 64 sqm cross-section and 90 m depth.
Construction technology:
Boring works executed through new Austrian tunnelling method (NATM). Excavation works are executed through drilling and blasting works, supporting with shotcrete reinforced by steel fibres with SN anchors. Drilling works are performed with drill slip form cars Tamrock Axera T 11, T 08 with extended mounts which allow drilling up to 5 m length of meshing. Putzmeister WKM 133 is used for shotcrete support. Mucking material is loaded in tunnel with wheel loader Volvo L 180 E equipped with side dumping. Mucking material removal from tunnel is executed by moulds, trail sets and tunnel conveyor belt system.
Contract sum: 130 mil. SKK
Construction period: March 2005 – June 2006
