Underground hydroelectric powerstation in Iceland

Underground hydroelectric powerstation in Iceland

Construction of underground hydroelectric powerstation

Client: Landsvirkjun (the National Power Company)

Superior Contractor: FOSSKRAFT J. V., Reykjavik, Iceland

Structures description and completed works:
Project: Kárahnjúkar Powerstation KAR 15 with service capacity 690 MW.
Company executed works at construction of underground hydroelectric powerstation Kárahnjúkar in Iceland.
Boring works were executed through new Austrian tunneling method (NATM) – drilling and blasting works.

Completed structures:

• cable tunnel with 14.8 sqm cross-section and 960 m length for conduction of electric power from underground trafostation,
• drainage tunnel with 68.8 sqm cross-section and 1 400 m length for water drainage from turbines,
• air tunnel with 5.5 sqm cross-section and 92 m length for aeration of underground engine room,
• underground engine room of 119 m length, 14 m width and 35 m height,
• underground trafostation of 103 m length, 13.5 m width and 16 m height,
• feeder corridors to turbines with cross-section from 16 sqm to 5 sqm and cca 225 m of total length,
• drain corridors from turbines to drainage tunnel with 14.3 sqm cross-section and 310 m total length.

Construction technology:
Excavation works were executed through drilling and blasting works, supporting with shotcrete reinforced by steel fibres with SN anchors. Drilling works were performed with drill slip form cars Tamrock Axera T 11, T 08 with extended carriages which allowed drilling up to 5 m length of meshing. Putzmeister WKM 133 was used for shotcrete support. Mucking material was loaded in tunnel with wheel loader Volvo L 180 E equipped with side dumping. Mucking material removal from tunnel was executed with lorries Mercedes DB 3331 6×4.

Contract sum: 122 mil. SKK

Construction period: November 2003 – December 2004