Iceland TBMs Make a Strong Finish and Tie a World RecordThe Kárahnjúkar hydroelectric project includes approx. 72 km of tunnels that will transfer water to a powerhouse in the Fljótsdalur valley. From the powerhouse, the water is carried through a tailrace tunnel that opens into the Fljótsdalur valley. From the mouth of the tunnel, the water is discharged through a tailrace canal into the course of the glacial river Jökulsá í Fljótsdal, where the surface level of the river will be approximately 26.5 m above sea level. Other impressive structures within the Kárahnjúkar scheme are five dams (Kárahnjúkastífla, Desjarárstífla, Sauðárdalsstífla, Kelduárstífla, and Ufsarstífla), two reservoirs (Hálslón and Kelduárlón) and the Ufsarlón pond. Full operation of the power station will be achieved in October 2007. Visit www.karahnjukar.isThe main tunnelling contractors hired by project owner Landsvirkjun are Impregilo on contract KAR-14, the Fosskraft JV (Hochtief, E. Pihl & Son, Istak and Iceland Prime Contractor) on contract KAR-15 and Arnarfell on contract KAR-21. The power scheme will generate 690 MW annually for the Alcoa aluminum smelting plant. Construction supervision of the dams and headrace tunnels (KAR-14) has been commissioned to Mott McDonald, three Icelandic engineering firms - Línuhönnun, Hnit, and Fjarhitun -, Sweco, Norconsult and Coyne et Bellier. Visit www.mottmat.com, www.sweco.se, www.norconsult.no and www.coyne-et-bellier.frThe construction supervision of the power station and associated tunnels has been commissioned to Lahmeyer International and four Icelandic partners, i.e. Honnun, Almenna, VSO, and Rafhonnun. Visit www.lahmeyer.de, www.honnun.is, www.almenna.is, www.vso.is and www.rafhonnun.is Contract KAR-14Water is carried from the Hálslón reservoir through an underground headrace tunnel eastward to a juncture with a diversion tunnel from the Ufsarlón reservoir. From there, a single tunnel continues northeast to the Teigsbjarg escarpment. Through this arrangement, the storage of the Hálslón reservoir can be regulated so as to maximise the use of the water flow in both of the glacial rivers for the power station. The tunnel between the Hálslón reservoir and the Teigsbjarg escarpment is 39.6 km long, approximately 7.2 m in diameter and largely full-face bored. The tunnel from the Ufsarlón reservoir is over 13.3 km, 5.5 m in diameter and also full-face bored to a large extent. Access to the tunnel is via four adits totalling 6.9 km, one at the Hálslón reservoir, one in the Glúmsstadadalur valley, one at River Axará and one at the Teigsbjarg escarpment.On contract KAR-14, Impregilo has put at work three Robbins TBMs for the 39.6 km Hálslón-Teigsbjarg headrace tunnel. The first TBM breakthrough was on 9th September, 2006. The Robbins main beam TBM (TBM 1) finished boring the 14.6 km-long section of the headrace tunnel, two years after the drill started its journey between the Hálslón reservoir and Fljótsdalur valley. On the same day, a second Robbins TBM (TBM 2) tied a world record in the 7 to 8 m diameter range. The machine bored 92 m in 24 hours. Another Robbins machine achieved this same feat on the Epping to Chatswood rail tunnels in Sydney, Australia in 2005. A third TBM (TBM 3) is also at work at the Kárahnjúkar scheme. Click here, here and here. Visit www.robbinstbm.com and www.impregilo.itThe performance of both Iceland machines is especially impressive considering the geology of the tunnels. All three TBMs boring on the headrace tunnel experienced heavily fractured ground and water inflows into their sections of the headrace tunnel. Despite these problems, the TBMs are on schedule. TBM 1 finished its bore on time despite technical difficulties with the conveyor belt. These problems began to surface when the machine was half way through, making the job harder because of the sheer length of the belt. The belt system is one of the longest of that kind in the world and many motors are needed to coordinate the flow of the rock from the tunnel. Nevertheless, TBM 1 averaged 643 m per month in 2006. TBM 1 is being dismantled inside the headrace tunnel at the moment. Impregilo is negotiating at the moment for a potential re-use of TBM 1 on another project.The TBM emerged with very minimal machine wear even after boring through hard basalt, mober and pillow lava geology of up to 300 MPa UCS. The machine was expected to finish at an earlier date but the conveyor belt system has been making the job harder because of the sheer length of the belt. The 7.23 m-diameter TBM 2 is scheduled to finish boring its 10.4 km-long section of tunnel at the end of September. Once boring is complete, the machine will be transported and reassembled to begin boring an 8.7 km-long section of the headrace tunnel from the Jökulsá river diversion to Ufsarlón reservoir in the first quarter of 2007. The tunnel will add to the water supply capacity of the powerhouse by connecting the Ufsarlón reservoir to the main headrace tunnel.TBM 2 drilled 92 metres on 9th September, 2006. This was the longest a TBM had ever drilled in a day at the Kárahnjúkar scheme. The record was set at the same time the breakthrough of TBM 1 was being celebrated. One milestone followed the next. TBMs 2 and 3 are drilling towards each other and as of 27th September, 2006 there were 900 metres left between them for the last breakthrough in the main headrace tunnel. According to original plans, TBM 2 only had 50 metres to go until the end of its job. But it was decided it would continue to drill for a longer time before it will be turned around and made to drill in the direction of the Ufsarlón pond. The reason for this is that it is doing much better than TBM 3 due to better conditions on its path, so that it was decided that it would continue its work beyond its original destination. TBMs 2 and 3 are expected to meet each other by the end of October. The determination of the meeting point between TBM 2 and TBM 3 is constantly changing according to alternating, more or less favourable geology between the two drives throughout tunnelling. TBM 3 will excavate approx. 1.2 km more. Compared to the situation two or three months ago, TBM 3 will excavate less than planned. TBM 3 was stopped on 8th July, 2005 to be partially dismantled, turned 180° and relaunched downstream to bore the headrace tunnel II. TBM 3, launched initially from Adit 3, has dug the approximate 2.5 km adit, approx. 5.2 km of headrace tunnel upstream and is now driving approx. 6.7 km of headrace tunnel downstream. Click here to see the status of works. The red part of the Jökulsá tunnel will be finished next year or early 2008.The bedrock in the project area is formed by lava flows and sedimentary Moberg interbeds of several types. Basalt is classified in the following petrografic typologies: tholeiitic basalt, olivinic basalt and porphyritic basalt. The nature of sediments varies according to the layout of lava layers within the rock mass. The lower layers are basically thin and tufaceous while the upper layers, comprising glacial conglomerates and till deposits, have been shaped by cold climate. The thickest layers are made up of sedimentary fluvioglacial rocks, mainly conglomerates and sandstone. Very large water inflows from aquifers have been encountered during the tunnelling phases, with sometimes peaks of over 1,000 litres per second.Impregilo employs eight shotcreting machines (four Aliva 500 wet mix units, an Aliva 504 portable unit and three Aliva 263 units) to support the tunnel. The shotcrete is reinforced with Sika fibres. Other support techniques are Orsta bolts, Metallegno steel arches and Tuxor welded wire fabric. Visit www.sika.ch, www.orsta.com, www.metallegno.com and www.tuxor.itThe muck is transported by a Continental Conveyor belt. The maximum length of a section is approx. 16 km. The total installed conveyor belt length is about 38 km. Visit www.continental-conveyor.co.ukAdits 1, 2 and 3 have been bored both using the drill/blast method and TBM. When blasted, Sandvik underground drill rigs have been used. At Adit 1, a Tamrock Axera T11 three-boom jumbo was used, with a Cat wheel loader. For Adit 2, 1.5 km was excavated with an Axera T11, and mucking with a Toro 007 LHD, and 1.5 km with TBM. For Adit 3, 500 metres have been blasted by an Axera T08 two-boom jumbo, with Cat loaders, and 2.5 km by TBM. Astra trucks were employed at the blasted sections of the three adits. Adit 1, which is at the end of the headrace tunnel, was completed in 2003. Visit www.tamrock.sandvik.com, www.toro.sandvik.com, www.cat.com and www.astraspa.it Contract KAR-15At the Teigsbjarg escarpment, two 400 m-long penstocks will run vertically in pressure shafts from the headrace tunnel to the Kárahnjúkar underground powerhouse, which is located approximately 800 m within the escarpment. The penstocks are steel-cased, approximately 3.5 m in diameter and branch off at their lower ends to feed the turbines and generators of the power station.The powerhouse will be approximately 115 m long, 14 m wide and with a maximum height of 34 m. It will house six generating units with associated apparatuses and have an installed capacity of 630 MW. Proud crew celebrates breakthrough of Robbins TBM 1 at Kárahnjúkar on 9th september, 2006 Beside the powerhouse there will be a 103 m-long, 13 m-wide and 16 m-high transformer room. The main transformers of the power station will be located in this room. The transformers will step up the electric current produced by the generating units to 245 kV.Access to the powerhouse and to the transformer room will be through a 1 km-long 7.5 m x 7.2 m underground tunnel extending from the Fljótsdalur (Nordurdalur) valley located at a point approximately 2 km southwest of the farm Valthjófsstadur. Just outside the access tunnel there will be a service building housing, among other things, a control centre and staff facilities. A separate 4 m x 4 m cable tunnel of about the same length will extend from the transformer room to the switchgear house, located at a short distance from the service building. The contract also includes a discharge tunnel and a 1.3 km, 9 m x 9 m tailrace tunnel.For the cable tunnel, Fosskraft used a Tamrock Mini 206, with Komatsu wheel loader and Astra trucks, an Axera T08, with Cat wheel loader and Mercedes trucks at the access tunnel and an Axera T11, with also a Cat wheel loader and Mercedes trucks for the tailrace tunnel. Visit www.fosskraft.is and www.komatsueurope.comContract KAR-21Icelandic contractor Arnarfell broke through on 1st September, 2006 on Adit 4 in the headrace tunnel. Originally, TBM 3 was intended to finish that part of the tunnel (383 m) but when it was decided to turn it around, the remaining distance was dug using the drill/blast method. Visit www.arnafell.isArnarfell is also building the Ufsarveita diversion, consisting of a 3.5 km 6 m-diameter drill/blast section of the Ufsarlón headrace tunnel, by means of two Axeras T11 and Dyno Nobel explosives. For support, crews spray shotcrete reinforced with Sika fibres, by means of two Sika-Putzmeister PM 500 shotcrete units and install steel bars. Breakthough of the 3.5 km Ufsarlón headrace tunnel is scheduled in early 2007. Visit www.dynonobel.com and www.putzmeister.deArnarfell is also responsible for a 50 m-long headrace tunnel that goes under the dam at Ufsarlón pond, a 60 m-long tunnel for the Jökulsá river diversion and a tunnel right above the powerhouse cavern. Filling of the Kárahnjúkar dam commenced on 28th September at 9:00 a.m. Click is/14. Read E-News Weekly 50/2003, 12/2003, 45/2002, 19/2002, 12/2002 & 2/2002. 40/06. Tunnels Approx. 72 km Headrace from Hálslón (dia: 7.2-7.6 m) 39.6 km Headrace from Ufsarlón (dia: 6.5 m) 13.3 km 4 adits to headrace (dia: 7.2-7.6 m) 6.9 km 2 diversion tunnels and adit at dam 2.4 km Grouting galleries at dam 0.5 km Surge tunnel (dia: 4.5 m) 1.7 km 2 diversion tunnels Hraunaveita (dia: 4.5 m) 3.7 km 2 vertical pressure tunnels (dia: 4 m) 0.8 km Access tunnel to power station (dia: 7.5 m) 1 km Tailrace tunnel (dia: 9 m) 1.3 km Cable tunnel (dia: 4 m) 1 km Contracts Progress week 37 Progress so far % Total size  KAR-14 Hálslón headrace tunnel, TBM 1*  Work finished  14,656 m  100  14,656 m  KAR-14 Hálslón headrace tunnel, TBM 2  233.3  m  8,514.3 m  95.4  8,927 m  KAR-14 Adit 2, TBM 2  Work finished  1,457.6 m  100  1,457 m  KAR-14 Hálslón headrace tunnel, TBM 3    Work finished  5,198.2 m  100  5,198 m  KAR-14 Adit 3, TBM 3  Work finished  2,624.4 m  100  2,625 m  KAR-14 Headrace tunnel II, TBM 3    241.7 m  5,852 m  87.7  6.678 m  KAR-14 Total length of drilled tunnels  475 m  38,302.8 m  96.9  39,491 m            KAR-14 Jökulsá headrace tunnel, TBM 2  Work not started  0  0  8,697 m  KAR-14 Adit 4, D&B  Work finished  383 m  100  383 m  KAR-14 Ufsarlón headrace tunnel  0 m  552 m  99.6  554 m  KAR-21 Ufsarlón headrace tunnel, D&B  0 m  2,749 m  78.5  3,500 m            KAR-11 Main dam fill                 Work finished  8,433,616 m3  100  8,440,000 m3  KAR-11 Concrete coat of the main dam   0 m2  76,665 m2  82,8  92,555 m2 * Includes Adit 1