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Four Atlas Copco Drill Rigs at Work in Vielha

Four Atlas Copco Drill Rigs at Work in VielhaThe existing Vielha tunnel, named Alfonso XIII, was inaugurated in 1948 and was developed during the reign of King Alfonso XIII. It is over 5,240 m in length, which makes it the second longest in Spain behind the Somport tunnel that connects the Huesca province with France. It is a two-way single-tube tunnel with two 3 m-wide lanes and two 50 cm-wide pavements. The gradient is 5%. New safety rules in Europe, with the disasters at the Mont Blanc, Tauern and Saint Gotthard tunnels in background, induced the Spanish Ministry of public works to double the existing tunnel with a new safer tube parallel to it. The new Vielha tunnel, named Juan Carlos I, is located in Vall d'Aráin Léda province (Catalonia), between km 150.9 and km 156.2 on road N-230, section Vilaller-Vielha.The project includes the construction of a new bidirectional tunnel, 5,230 m in length. The carriageway will accommodate three 3.5 m-wide lanes, two shoulders (0.5 and 1 m) and two 1 m-wide pavements. The central lane will be reversible and two of the three lanes will be used for north-south traffic. The headroom is 5.29 m with a maximum gradient of 4.57%.Once the new tunnel is commissioned, the existing old tunnel will be earmarked for heavy vehicles carrying hazardous cargos and used as an emergency tunnel for rescue in case of incidents in the new tunnel.The project designer is Idom. Construction was awarded in January 2002 to UTE Túnel de Vielha, a JV headed by OHL (50%) with Copcisa (25%) and Comsa (25%) as partners. Their contract is worth €128 million and they have 39 months to complete the tunnel. The contract includes all civil engineering of the new tunnel and its accesses, installations and equipment, and the ventilation and central control buildings. The tunnel will be ready in June 2005. Visit www.idom.es, www.ohl.es, www.copcisa.com and www.comsa.com. The technical assistance to work control and construction supervision has been awarded to Sener for €3.6 million. Visit www.sener.esMaximum SafetyThroughout the tunnel, there will be 25 safety niches on one side and 25 fire niches on the opposite side, each situated 200 m apart. Twelve 12 m-long shelters, spaced out every 400 m, connecting with the cross passages leading to the old tunnel, will allow for evacuation in the event of an incident. Eight lay-bys every 550 m (four on each side) will allow to stop in case of necessity.The tunnel will be equipped with semi-transverse reversible ventilation. In case of accident, the system will confine a fire and extract smoke through a false ceiling.  House-sized ventilation stations will be located at both ends.Other noticeable equipment include 67 CCTV cameras, 12 variable message panels, traffic lights, barriers to prevent cars from entering the tunnel, SOS posts, a network of telephones, radiocommunications and loudspeakers, a fire detection system, water supply (fire hydrants at the right wall and sprayers in ceiling) and automatic incident detection (AID). The technical management of all these systems will be centralised in a new control centre located 400 m from the south portal.The road surfacing will be vibrated concrete on thin concrete. It is fireproof, thus avoiding fire propagation peculiar to asphalt mixtures that contain bitumen. Under the roadway, there will be a 3 m x 2.25 m service tunnel for the electric wiring and water duct that will feed the hydrants of the anti-fire niches.GeologyFrom south to north, towards Vielha, the massif is comprised of moraines (210 m), approx. 420 m of fractured granite, then about 2,100 m of massive granite. Then appears, in contact with the granite, the Civis formation, a highly metamorphic rock of the Devonian period consisting mostly of slates. This will be the trickiest zone. After that, there is a 1,600 m portion with quartzites, mixed with shales in the next 250 m. The alignment ends on the north side crossing Carboniferous shale and blackish Silurian shale (approx. 420 m).Advanced Engineering at 1,600 mThe excavated cross section is 127 m2. The south drive is descending with a gradient of 4.57%. Once lined, the tunnel's cross section will be 95 m2. The south portal lies at 1,595 m and the north entrance at 1,396 m. Weather conditions can be extreme as was the case in late 2002 with temperatures below -20°C. Work takes place all year round, winter included, in three shifts from Monday 8 am to Saturday 2 pm. Each team is composed of a chief, six workers, a mechanic and an electrician. There is still one year of tunnelling prior to breaking through. A cycle takes 14 hours.The tunnelling method is drill/blast. The JV decided to acquire four Atlas Copco drill rigs, two of them being WL3 C models for the main tunnel and two L2 C rigs for the shelters and cross passages to the existing tunnel. Visit www.atlascopco.com, www.facedrilling.com and www.drillersclub.comThe Rocket Boomer WL3 C is a fully computerised jumbo with three booms and basket, to handle sections up to 155 m2. The Rocket Boomer L2 C is a twin boom drill rig, for up to 90 m2 sections. Both are equipped with COP 1838 rock drills and Secoroc drill bits. Visit www.atlascopco.com/rde/esp and www.atlascopco.com/secorocThese machines feature the CAN-bus electronic system. The CAN-bus (Controller Area Network) is an intelligent software that can be adapted to the number of booms, the level of automation and the introduction of new functions without need to install an expensive and powerful computer. This system is reliable, flexible and easily expandable, allowing new units to be added anywhere along the data bus, without adding another cable.To improve the reliability of the system for a multi-boom rig operating in the full automation mode, two-level circuit communication has been implemented. The upper level talks to the whole rig, and the identical lower circuit talks to each boom circuit. All signalling on angles in the boom joints is restricted to the boom circuit, while the upper level system advises only on the basic position of each boom.The advantage of this setup is that a lower level circuit fault on one boom caused, perhaps, by falling rock or pinching against the sidewall, will not hamper the operation of the other booms. The software is split into a number of blocks, and individual blocks can be added, deleted or modified. Auto-collaring and anti-jamming functions are incorporated into the system, and the combination of these, and improved regulation of the double dampened 1838 drill machines, produces favourable drill steel costs.The operator can control the whole rig from one panel, and he can communicate with any of the booms. This means that only one operator is needed for two booms, or all three booms if it is a three-boom rig. This also applies to short holes because the boom movements and feed positioning are carried out without the assistance of the operator. Jamming of the drill steel no longer occurs, saving time and giving straighter holes.Another important feature with the CAN-bus rig is that these have a built-in diagnostic procedure for the electronic system, making it easy to find and repair faults. The electronic components on the CAN-bus rigs are common and interchangeable, thus requiring fewer parts at site. As per the maintenance contract signed between the JV and Atlas Copco, there is a mechanic on secondment at the site and an independent spare part warehouse at each portal.South DriveAt the south portal (Vilaller side), construction started with a canopy of spiles in the first 210 m of moraine. The 15 m-long umbrella vaults were composed of 65 steel pipes, 89 cm in diameter. A Tamrock 316G three-boom drill rig with basket has been used to drill the holes. Excavation of the top heading was then performed using a CAT 325 excavator and when 12 m had been bored, a new canopy was installed with a 3 m overlap on the previous one. The support in this soft ground stretch consists of HEB 180 steel arches and two layers of shotcrete, with and without fibres. Visit www.smc.sandvik.com and www.cat.comWhen the granite was reached, a ramp was built downward to open the full section. From there on, the first Rocket Boomer WL3 C for the main tunnel and the first Rocket Boomer L2 C for the shelters and cross passages began their job. Their twins are working at the north drive.The Rocket Boomer WL3 C commenced in August 2003. Average progress is 7 m/day, 40 m/week and 175 m/month. As of mid November 2003, progress at the south drive had reached 900 m. The Rocket Boomer L2 C began the first shelter and transverse escape corridor in September. As of mid November, progress equalled 40 m. The south drive is 3 weeks ahead of schedule.The drill pattern includes 150 holes spread out on the 127 m2 section. They are 5 m in length and 51 mm in diameter, with four cylindrical empty bigger holes of greater diameter (102 mm) drilled in the lower part of the face, symmetrically to the tunnel's vertical axis. The explosives are Goma-2 (26 and 32 mm) supplied by Unión Española de Explosivos. Visit www.uee.esThe support in the granitic zone is made of 3 cm of fibre-reinforced shotcrete, a second layer of identical thickness without fibres and Atlas Copco's Swellex Mn 12 rockbolts (13 units by lineal metre). All the steel fibres used in the tunnel are supplied by Bekaert. Visit www.swellex.com, www.rockreinforcement.com and www.bekaert.comThe Swellex bolts are placed using the basket boom of the jumbo. Also, three Normet's Himec platforms are used (two at the north drive and one at the south heading) to carry out tasks such as installing wire mesh or loading the explosives. Visit www.normet.fiFour Putzmeister's Wetcrete, two WKM 102 and two WKM 103, are used for shotcreting. There is one unit of each model at each drive. Visit www.putzmeister.de or www.putzmeister.esThroughout excavation, the tunnel is ventilated by means of Zitrón fans. At the south portal, there is a fan outside that takes the air in. At the north face, there are two fans taking the air from the existing tunnel through cross passage number 9 and blowing towards one side and the other. Visit www.zitron.comThere is water ingress. Because of the gradient, the water stays at the face, which requires pumping round the clock using Flygt pumps. Visit www.flygt.comNorth DriveProgress at the north drive (Vielha side) had reached 1,700 m in mid November. Sixty metres had been bored on cross passage number 12, 54 m on number 11 and 2 m on number 10. Tunnelling of the main tunnel began with the widening to 127 m2 of an existing 1,350 m-long 60 m2 ventilation tunnel that connected with the existing tunnel. Work began in December 2002 using the Tamrock 316G jumbo. The drill pattern included 72 holes, 5 m in length and 48 cm in diameter. Goma-2 explosives (26 mm ) were used.The support is made up of a 5 cm fibre-reinforced shotcrete layer, Swellex Mn rockbolts (one unit per m2), wire mesh, more bolts (5 units per lineal metre) and 6 cm of shotcrete without fibres.There is a fault approximately 400 m after the end of the widened ventilation tunnel. It was therefore decided to reduce the excavation to the top heading. The second Rocket Boomer WL3 C drills 98 holes in the upper part of the face and UEE's Goma-2 explosives (26 mm) are used for the blasts. HEB 180 and TH 21 steel beams supplied by Auxiliar de Entibación are used for the support. Visit www.guiadeprensa.com/metal%202000/const%20metal%20mecanicas-estruc/entubicion.html. The fault will be crossed implementing four lengths of umbrella vaults. Incoming water is more important at the south drive with volumes of 35-40 litres/sec. Thanks to the natural descending gradient, the water does not stay at the face and flows towards the exit. The JV is taking advantage of such amounts of water to collect and treat it in two 12 m-diameter tanks installed outside the north portal. With a flocculating agent, the altered pH is corrected and the particles settle on the bottom.Mucking-outThe total tunnel system, including the cross passages between the new tunnel and the existing one, will generate 671,337 m3. The excavated material is transported to dumps at the north portal and 5 km away from the south portal. The spoil not reused is transported to four dumps (3 at the south portal and one at the north one). The granite is processed in a crushing plant to produce aggregates. There is one concrete plant at each portal. The machinery used for the mucking-out at the south drive include five dumpers Volvo A25 and a loader Komatsu WA600. Visit www.volvo.com/dealers/en-gb/vcegb/Products, www.komatsueurope.com and www.kesa.es. A loader CAT 968 and two dumpers Volvo A25 are used to remove the spoil at the north drive. Visit www.cat.com. Click es/57. 49/03.AcknowledgementsTunnelbuilder.com wishes to thank Pedro Garcí­a Borjabad (project administrator), Ángel Marti­n Aragón (project manager), Carlos Montenegro Ferreyra (tunnelling manager), Ana Laporta, Ángel Rodrígu­ez Espina (tunnelling manager, south drive), Laudelino González (technical manager) and Miguel Jurado (tunnelling manager, north drive) at UTE Túnel de Vielha as well as Manuel Lorente, Darsy Castillo and Fernando Menéndez Chicharro at Atlas Copco SAE for allowing and organising the visit to the jobsite. Reproduction of this article permitted quoting Tunnelbuilder.com as source where it was first published.