Drill and Blast at Hedins Fjord Tunnels in IcelandThe Hedins fjord tunnels in northwest Iceland consists of two-lane tunnels stretching for 10,575 metres. The first, 3,650 m-long tunnel connects the Siglu fjord and the Hedins fjord and the second tunnel, 6,925 m in length, links the Hedins fjord and the Olafs fjord. The two tunnels are connected by a bridge, which is to be built in Hedins fjord.The excavated cross sectional area of the two-lane tunnels is 52.83 sq m and in the sections with an emergency stop lane, the cross-section is 75.25 sq m. The width and height of both tunnel tubes are 8.6 m and 7.16 m, respectively. The traffic lanes are 3 m wide. There are no other underground structures than the tunnels to be excavated.The tunnels are built by Czech contractor Metrostav and Hafell for the Icelandic road administration Vegagerdin. The engineering supervisor is Iceland-based company Geotek. Click is/19. Visit www.metrostav.cz, www.hafell.is, www.geotek.is and www.vegagerdin.is/english GeologyThe tunnels are driven in hard rock, without a systematic lining, through effusive rock throughout their lengths. The tunnel alignment passes through sub-horizontal beds of basalt, which are interlayered by tuffs and tuffites. The basalt beds are 10-20 m thick, the tuff/tuffite layers are about 1 m thick. Unfavourable geological conditions were encountered during the excavation, with significant inflows of both cold and hot water. Drill and blastThe excavation is performed using two Tamrock drill rigs with Sandvik tools. There are two to three rounds per day, depending on geology. Visit www.miningandconstruction.sandvik.com or www.sandvik.comTunnelling of the Siglu fjord tunnel commenced in September 2006 and the tunnel has broken through on 21st March, 2008. The Olafs fjord tunnel commenced in November 2006. The length excavated is 2,700 m as of March 2008. Breakthrough is expected at the end of 2008 or beginning of 2009. Primary supportFor support, cement grouted Orsta Stal rock bolts (3, 4, 5 and 6 m long, 20-25 mm in diameter), mechanically fastened Orsta Stal CT-bolts (3, 4 and 5 m long, 20 mm in diameter), steel mesh, shotcrete grade ? C40, unreinforced or steel fibre-reinforced with SikaFiber-CHO 65/35 NB, and BASF additives (Meyco SA 162 setting accelerator, Glenium SKY 580 super-plasticiser and TCC 735 concrete improver). Shotcreting is placed by two Meyco shotcrete manipulators. Visit www.orsta.com and www.ct-bolt.com and www.basf-cc.comWhen the tunnel excavation is completed, the tunnel will be covered with waterproofing and frost protection by means of a PE membrane. The final lining in the mined part of the tunnel, where necessary, will consist only of shotcrete and rock bolts. Mucking-outThe rock is loaded on Komatsu dumpers by Brøyt front-end loaders (tunnel excavators) and transported to a stockpile in front of the tunnel. Volvo wheeled loaders are also used. View pictures here. Visit www.komatsu.com/ce, www.volvo.com/constructionequipment and www.meyco.basf.com 17/08.