Bolu Tunnel Breaks Through in TurkeyTurkish Prime Minister Recep Tayyip Erdogan and Italian Ambassador to Turkey Carlo Marsili presided on 4th September, 2005 the breakthrough ceremony of the right tube of the USD234 million Bolu tunnel on the Gumusova-Gerede section of the Ankara-Istanbul highway. The left tube broke through on 28th July, 2005. The client is the General Directorate of Highways under the Ministry of Public Works and Settlement. Yüksel Proje is consulting engineers. The designer of the tunnel is Geoconsult ZT. The Bolu tunnel is being constructed by the Italian contractor Astaldi. After the tunnel and highway are completed, drivers will travel between Ankara and Istanbul in three and a half hours. The present duration is four to five and a half hours. The tunnel will enter service at the end of 2006, reducing road accidents risks and the time spent to cross the Bolu mountain pass from 30 to 5 minutes. Click tr/16. Visit www.bayindirlik.gov.tr, www.yukselproje.com.tr, www.astaldi.com and www.geoconsult.atBecause of poor soil conditions, the excavation area is as big as 275 sq m although the final section will be 100 cu m. There are emergency cross passages at every 500 metres, suitable for vehicles. Their excavation area is about 87 sq m and the final section will be 43.88 sq m. The tunnels are being bored through highly tectonised and faulted sequences of rocks. The fault systems within this region are classified as seismically active at the first degree. The Bolu tunnels are separated by about 50 m. Ground cover above the tunnel crown reaches 250 m maximum, with the majority of the tunnels under a cover of 100-150 m. Pre-tunnelling groundwater levels were 45%-85% of the overburden cover. Generally the ground exists as subangular blocks of hard material within a clayey matrix. The proportion of the clayey matrix varies substantially between the different geotechnical units so that the worst ground comprises wide zones of uniform pure fault gouge clay. The proportion within the clayey matrix by volume varies from about 30% to 100%. In some zones the ground consisted of uniform fault gouge with no hard inclusions comprising the minimum favourable conditions. Such zones have been encountered in thickness of up to 50 m or more along the tunnel alignment and also extend vertically (80 m to 120 m of poor material overburden). Along some sections of the tunnel, the dip of the slicken-sided surface has presented towards the face the potential of large blocks sliding on such surfaces. Face bolting was used to reduce this risk.The geology consists of highly tectonised and intermixed series of mudstones, siltstones and limestones, with stiff heavily slicken-sided highly plastic pure fault gouge clay. The studies carried out and a report prepared by Prof. A. Barka and associates showed that the Bakacak fault is approximately 10 and 15 km long and it crosses the Bolu tunnels within a 200 m-wide zone. The fault in this area is basically oriented east-west and crosses the tunnel alignment almost by a right angle between chainages 62+800 and 63+000 (left tunnel). This fault traces are north dip angle on the geological cross sections and they cross the tunnel by a fault clay, 75 m wide in the left tunnel and 91.5 m in the right tunnel. This fault gouge clay layer is between metasediments (metasiltstone, metalimestone, quartzitic limestone, crystallized limestone), blocks with low-to-medium plastic, firm-to-stiff sandy, silty or clayey fault gouge matrix. This fault gouge material is at the interface between Asarsuyu-Elmalik geological formation. The fault gouge material encountered at the tunnel level is formed by two units: Unit 1 - dark brown, high plastic, stiff to very stiff slicken-sided surface and Unit 2 - reddish brown, medium plastic, very stiff to hard slicken-sided surface. These materials form the Bakacak fault.At the beginning of the excavation, blasting was used since there was some good soil conditions (approx. 400 m). The remaining part of the tunnel has been excavated by conventional excavator equipped with hydraulic hammer. Every tube had two faces. Each tunnel face employed a CAT 235C ME excavator with jack hammer (250 hp), a CAT 966F loader (220 hp, 3.8 cu m), a CAT 9560E loader (167 hp, 3 cu m) and Astra trucks BM 64.26 (260 hp, 14 cu m, 20 tons) for the mucking-out. Visit www.cat.com and www.astraspa.comWiremesh, MBT shotcrete with Bekaert's Dramix steel fibres, steel ribs, Atlas Copco MAI self-drilling anchor bolts and steel pipes for forepoling have been used for support. The equipment used include a Scamac SC271 shotcrete pump (160-115 hp), transmixers for concrete - Astra-CIFA BM 64.31 (260 hp, 10 cu m), Iveco-CIFA 330 (2 hp, 10 cu m) and Iveco-CIFA 300 (260 hp, 9.5 cu m) - a Dieci 70 mobile telescopic elevator (100 hp, 7 tons) for steel ribs installation, an Atlas Copco GD Anker M400 pump (600 l/h) for bolt injection, an Hydrolice truck drill, a Puntel PX 100 (120 hp) and a Puntel JET1 106h for forepoling and boreholes, an Iveco-CIFA 300 pump (260 hp, 64 cu m/hr) for Bernold lining, and an Astra-CIFA BM21 pump (200 hp, 55 cu m/hr) for steel shutters. Visit www.degussa.com, www.bekaert.com/building, www.rockreinforcement.com, www.cifa.com, www.dieci.com and www.bernold-ceresola.com The remaining works to be done include 11.5 m of Bernold concrete, 148.5 m of final lining and 160 m of warterproof membrane in the right tunnel and 81 m of final lining and 81 m of waterproof membrane in the left tunnel. The electro-mechanical equipment will be installed by a subcontractor of Astaldi. Bids have been receiced on 19th September and are being analysed. The Bolu tunnel forms part of a 26 km highway section. The official completion date is 15th December, 2006. Read more visiting www.tunnelbuilder.com/rockreinforcement/edition2pdf/page91.pdf 39/05.