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  • 1. EOSC547: EOSC547: Tunnelling & Underground Design g D g Topic 1: Geological Hazards in Tunnelling 1 of 46 Tunnelling Grad Class (2012) Dr. Erik EberhardtTunnel Construction: In the BeginningAll major ancientcivilizations developedtunneling methods. InBabylonia, tunnels were y ,used extensively forirrigation; and a brick-lined pedestrian passagesome 900 m long wasbuilt around 2180 BCunder the EuphratesRiver to connect theroyal p l l palace with the ith thtemple. Construction wasaccomplished by divertingthe river during the dryseason. 2 of 46 Tunnelling Grad Class (2012) Dr. Erik Eberhardt 1
  • 2. Tunnel Construction: In the BeginningThe Greeks and Romans both made extensive use of tunnels toreclaim land by drainage and for water aqueducts.6th-century-BC Greek water tunnel on theisle f S m d ii l of Samos driven some 1100 m through m th hlimestone with a cross section about 2 x 2 m. Perhaps the largest tunnel in ancient times was a 1600 m long, 8 m wide, 10 m high road tunnel (the Pausilippo) between Naples and Pozzuoli, built in 36 BC. 3 of 46 Tunnelling Grad Class (2012) Dr. Erik EberhardtTunnel Construction: In the Beginning In the AD 41, Romans used some 30,000 men to push a 6 km tunnel over 10 years to drain Lacus Fucinus. They worked from shafts 40 m apart and up to 125 m deep. Far more attention was paid to ventilation and safety measures when workers were freemen. 4 of 46 Tunnelling Grad Class (2012) Dr. Erik Eberhardt 2
  • 3. Tunnel Construction: In the Beginning Ancient construction was carried out using a succession of closely spaced shafts to provide ventilation. String line and plumb bobs were used for surveying. Ventilation methods were primitive, often limited to waving a canvas at the mouth of the shaft, and most tunnels claimed the lives of hundreds or even thousands of the slaves used as workers. To save the need for a lining, most ancient tunnels were located in strong rock, which was excavated by heating the rock with fire and suddenly cooling it by dousing with water causing the rock to spall. 5 of 46 Tunnelling Grad Class (2012) Dr. Erik EberhardtModern Beginnings: The ThamesTunnelling in soft, water saturatedground began with Marc Brunel whenhe invented the principle of shieldtunnelling and undertook a contract totunnel under the Thames between1825 and 1841. His shield consistedof 12 independent cells in whichworkers hand excavated the groundbehind a secure wall of ‘polingboards’. One board would be removedto provide access for digging, afterwhich it would be replaced and pushedforward by hydraulic jacks to re-engage th face support. the f tBrunel’s shield was 7 m high and 12 m wide, andenabled 36 miners to work the tunnel face atone time. The brickwork built right behind the‘shield’ served as an abutment for the wholeframe. On average, progress was 3-5 m/week. Harding (1981) 6 of 46 Tunnelling Grad Class (2012) Dr. Erik Eberhardt 3
  • 4. Modern Beginnings: The ThamesFlooding was aconstant problem forBrunel in tunnellingunder the Thames.In one such flood 6men drowned.Brunel’s complaint tothose offering adviceon tunnelling in suchdifficult conditions,“In every case theymake the ground tosuit the plan and notthe plan to suit theground”. Completed in 1843, Brunel’s tunnel is still in full use as part of London’s Underground railway system, exactly as built! 7 of 46 Tunnelling Grad Class (2012) Dr. Erik EberhardtModern Beginnings: The ThamesJames Greathead solved the problem of containing groundwaterduring the construction of subaqueous tunnels in loose soil, bycombining shield tunnelling with the use of compressed air during hisconstruction of the London Underground. James Greathead’s 2.5 m diameter circular shield, propelled by screw jacks, employed the first use of cast iron lining segments. This led to a considerable increase in the number of shield driven tunnels world-wide. At the beginning of the 20th century, the majority of the tunnels were built with Greathead shields. 8 of 46 Tunnelling Grad Class (2012) Dr. Erik Eberhardt 4
  • 5. Geotechnical Challenges: Gotthard Base Tunnel The Known Knowns, Known Unknowns, & Unknown Unknowns 9 of 46 Tunnelling Grad Class (2012) Dr. Erik Eberhardt AlpTransit In 1994 the Swiss voted an alpine protection article into their constitution, forbidding the expansion of road capacity in alpine regions. This forced the government to shift heavy goods traffic from road to rail. To accommodate this, voters approved the “Alptransit” project to build new tunnels through the Gotthard and the Lötschberg. 10 of 46 Tunnelling Grad Class (2012) Dr. Erik Eberhardt 5
  • 6. Reasons for the Base Tunnels Increasing Population Demands & Commercial Traffic - The Gotthard Road Tunnel, is the main north-south route through the g Alps, between Switzerland and Italy. - 18,000 vehicles/day pass through the Gotthard Road Tunnel. Safety Pollution Drivers going DGotthard Road through theTunnel Fire Gotthard Road(2001) – 11 Tunnel inhale aspeople killed many pollutants as if they smoked up to eight cigarettes. 11 of 46 Tunnelling Grad Class (2012) Dr. Erik EberhardtAlpTransit Base Tunnels 12 of 46 Tunnelling Grad Class (2012) Dr. Erik Eberhardt 6
  • 7. Tunnelling & Geology – The Swiss Base Tunnels World’s Longest Transportation Tunnels Length Completion Tunnel (km) Date Gotthard Base (CH) ( H) 57.1 . 2012* Brenner Base (AU) 55.4 2020 Sei-kan (Japan) 53.9 1988 Chunnel (ENG-FR) 50.5 1994 Loetschberg (CH) 34.6 2007 #30 Mount MacDonald (CAN) @ 14.6 km #43 New Cascade (USA) @ 12.5 km Gotthard Road Tunnel (CH) = 16.9 km Canada = 5 rail tunnels > 2 km USA = 4 rail tunnels > 2 km Switzerland = 42 rail tunnels > 2 km 13 of 46 Tunnelling Grad Class (2012) Dr. Erik EberhardtTunnelling & Geology – The Swiss Base Tunnels World’s Longest Transportation Tunnels COST: Length Completion Tunnel (km) Date 1998: $7.2 Billion 2011: $9 7 Billion * $9.7 Gotthard Base (CH) ( H) 57.1 . 2012* Brenner Base (AU) 55.4 2020 Sei-kan (Japan) 53.9 1988 1998: $3.2 Billion Chunnel (ENG-FR) 50.5 1994 2007: $4.3 Billion Loetschberg (CH) 34.6 2007 Modernisierung der Bahn Bauprogramm Gotthard San Gottardo Financing: 2000 2005 2010 2015 2020 2025 2000 Lötschberg 200710% Oil Tax 2000 Gotthard 2006 Zimmerberg 2012 2013 201815% Loans Neat 2006 Ceneri 201655% Heavy Vehicle Tax Ausbauten 2007 2011 St. Gallen – Arth-Goldau Verbindung 2011 201620% 1% increase in VAT Zürichsee – Gotthard 2000 1. Etappe 2005 Bahn 7.5.2_ Modern.Bahnen.Bauprogramm_98_0161_S 2011 2.Etappe 2022 2000 Rollmaterial Infrastruktur Lärmschutz Anschluss an 2002 2012 europäisches Hochleistungsnetz 14 of 46 Tunnelling Grad Class (2012) Dr. Erik Eberhardt 7
  • 8. Lötschberg Base Tunnel Length = 34.6 km Total tunnel system = 88.1 km 80% Drill & Blast Excavated material = 16 million tonnes 20% TBM 15 of 46 Tunnelling Grad Class (2012) Dr. Erik EberhardtGeological Challenges: Lötschberg Base TunnelBuried Valleys: burial is the consequence of glacial down cutting and alluvialdeposition. Buried valleys are a major concern in tunnelling as they areoften deep (!!), with unknown thicknesses, and filled with water saturatedsediments under high water pressures. The Th path of the Lötschberg passed under the th f th Löt hb d d th Gästern Valley, 200 m below the valley floor. It was estimated that the alluvial sediments extended 100 m below surface leaving 100 m of strong limestone to form the roof of the tunnel. In actuality, the buried valley reached depths of more than 185 m. By July 24, 1908, th t 1908 the tunnel had advanced such that l h d d d h th t only a thin wall of rock divided the working- face from the buried valley. Within seconds of that morning’s blast, 40,000m3 of water saturated sediments swept into the tunnel killing 25 men and filling the tunnel for a distance 1.25 km. 16 of 46 Tunnelling Grad Class (2012) Dr. Erik Eberhardt 8
  • 9. Lötschberg Base Tunnel: Geological Prognosis Loew et al. (2000) 17 of 46 Tunnelling Grad Class (2012) Dr. Erik EberhardtGeological Challenges: Lötschberg Base TunnelKarst:Given the porous nature of karst,large volumes of water and a highrisk of water ingress was 1.5m 1 5mexpected over a section about 3 d bkm long. It was constantlynecessary to carry out preliminaryboring in order to discoverwhether any large, water-filledkarst sink-holes might endangerthe tunnel driving operations. 18 of 46 Tunnelling Grad Class (2012) Dr. Erik Eberhardt 9
  • 10. Gotthard Base Tunnel Length = 57 km Sedrun shaft = 800 m Pillar = 40 m width Excavated material = 24 M tonnes 19 of 46 Tunnelling Grad Class (2012) Dr. Erik Eberhardt Gotthard Base Tunnel 20 of 46 Tunnelling Grad Class (2012) Dr. Erik Eberhardt 10
  • 11. Gotthard Base Tunnel: Geological Prognosis Loew et al. (2000) 21 of 46 Tunnelling Grad Class (2012) Dr. Erik EberhardtGeological Challenges: Gotthard Base Tunnel Potential Tectonic Max. Geologic Unit Key Hazard Unit Length Cataclastic Faults High pressure water Crystalline Massifs, 100 @ 5m inflow. Penninic Gneisses Weak Rocks (Phillites Strongly squeezing (Phillites, Crystalline Massifs 1.3 1 3 km Schists, Cataclasites) ground. Loew et al. (2000) Granites Rockburst. Crystalline Massifs >14 km Sugar Grained Water saturated (Par)autochthonous 200 m Dolomites debris inflow, Triassic Sediments cohesionless rock.The first Gotthard rail tunnel was constructed between1872-1882, and cut the travel time from Zurich to Milanfrom 27 to 5.5 hours. However, 310 men died and 877were incapacitated during construction of the 14.9 kmtunnel. Numerable challenges and harsh conditions wereencountered, many of which were augmented by the equallyharsh contract signed by the tunnel designer Louis Favre . 22 of 46 Tunnelling Grad Class (2012) Dr. Erik Eberhardt 11
  • 12. Geotechnical Challenges: Known Knowns Brittle Fault Zones Zangerl et al. (2006) 23 of 46 Tunnelling Grad Class (2012) Dr. Erik EberhardtBrittle Fault Zones - Water Inflows Loew et al. (2000)Fault zones may form highlypermeable conduits forgroundwater,groundwater leading to tunnelinflows. Encountering largequantities of water may lead toflooding of the excavation,especially if there is no outlet forthe water to drain to. 24 of 46 Tunnelling Grad Class (2012) Dr. Erik Eberhardt 12
  • 13. Brittle Fault Zones – Weak Ground Laws et al. (2003) Granitic Fault Rocks Aar Massif (3=5MPa) 25 of 46 Tunnelling Grad Class (2012) Dr. Erik EberhardtBrittle Fault Zones – Ground Support 26 of 46 Tunnelling Grad Class (2012) Dr. Erik Eberhardt 13
  • 14. Amsteg (June 2005) – West TBM ... West TBM crosses hydrothermally altered rock adjacent to fault zone, enounters flows of 2-3 l/s that flushes loose material into the cutter head. l h h d Ehrbar (2008) ... 5 month delay, $10 million cost. 27 of 46 Tunnelling Grad Class (2012) Dr. Erik EberhardtGeotechnical Challenges: Known KnownsSqueezing Ground – Tavetsch MassifSqueezing ground refers to weak,plastic rock material which displacesinto the tunnel excavation under thei h l i d haction of gravity and induced stresses.This squeezing action may result indamage/failure to the ground supportsystem, or require the costly re-excavation of the tunnel section. 28 of 46 Tunnelling Grad Class (2012) Dr. Erik Eberhardt 14
  • 15. Geotechnical Challenges: Squeezing Ground Ehrbar & Pfenninger (1999) 29 of 46 Tunnelling Grad Class (2012) Dr. Erik EberhardtSqueezing Ground Support Fabbri (2004) 30 of 46 Tunnelling Grad Class (2012) Dr. Erik Eberhardt 15
  • 16. Geotechnical Challenges: Known Unknowns Where ground possesses the ability to flow freely (i.e. “running ground”), for example with water saturated cohesionless materials, then special support and control p pp difficulties can arise. Sugar-grained dolomites (granular & cohesionless). 31 of 46 Tunnelling Grad Class (2012) Dr. Erik EberhardtGeotechnical Challenges: Running Ground Sugar-grained dolomites (granular & cohesionless). 32 of 46 Tunnelling Grad Class (2012) Dr. Erik Eberhardt 16
  • 17. Geotechnical Challenges: Running GroundThe tunnel will cross the Triassic Piora Zone, a highly weathered andfractured aquifer under high hydraulic pressure. Based on exploratorydrilling, it was found that the tunnel will pass ~250 meters below thebase of the aquifer through unweathered and unfractured dolomite/anhydrite-sequences.Considered thegreatest geologicalrisk to theffeasibility and ysuccess of thetunnel project, inNov. 2008 theTBM passed safelythrough the Piora. 33 of 46 Tunnelling Grad Class (2012) Dr. Erik EberhardtGeotechnical Challenges: Known Unknowns Rockbursts involve sudden releases of stored strain energy through the failure of strong rock. rock They manifest themselves through the sudden ejection of rock into the excavation. Rockbursting potential is of special concern in cases of deep tunnelling where high stress concentrations form due to overburden loads or tectonic activity. 34 of 46 Tunnelling Grad Class (2012) Dr. Erik Eberhardt 17
  • 18. Stress-Stress-Controlled Failure & Stress Path 1 Stress Concentration Unstable Stable Wedge In-Situ Stress Stress Path Relaxation 3 Kaiser et al. (2000) 35 of 46 Tunnelling Grad Class (2012) Dr. Erik EberhardtHigh Overburden – Spalling & Rock Bursting Baeret al. (2007) 2.4 ML – Mar. 25, 2006 1.6 ML – Nov. 6, 2006 36 of 46 Tunnelling Grad Class (2012) Dr. Erik Eberhardt 18
  • 19. Geotechnical Challenges – Unknown Unknowns Subhorizontal Faults 37 of 46 Tunnelling Grad Class (2012) Dr. Erik EberhardtFaido-Bodio:Faido-Bodio: “Unexpected” Faults Bonzanigo (2007) 38 of 46 Tunnelling Grad Class (2012) Dr. Erik Eberhardt 19
  • 20. Faido-Bodio:Faido-Bodio: “Unexpected” Faults 14’500 Tm EST-Ost 14’000 13’500 Amphibolite 14 500 14’500 Tm EST-West EST West 14 000 14’000 13 500 13’500 Faido Squeezing ground Bodio blocks TBM The total delay for y passing through these faults along this section: ... one year. 39 of 46 Tunnelling Grad Class (2012) Dr. Erik EberhardtFault Zones & the Faido Cross-Over Cross- Ehrbar (2008) Similar ground conditions (i.e. unexpected faults) at the Faido multipurpose cross-over station were responsible for a further 2-year delay and was over budget by more than 200%. 40 of 46 Tunnelling Grad Class (2012) Dr. Erik Eberhardt 20
  • 21. Faido-Bodio:Faido-Bodio: “Unexpected” Faults 41 of 46 Tunnelling Grad Class (2012) Dr. Erik EberhardtGBT: Other Geological ChallengesBodio 42 of 46 Tunnelling Grad Class (2012) Dr. Erik Eberhardt 21
  • 22. GBT: Other Geological Challenges  n´= n -  p f  normal deformation (i.e. closure)  “Poison ratio” effect Zangerl et al. (2008) 43 of 46 Tunnelling Grad Class (2012) Dr. Erik EberhardtGBT: Other Geological Challenges Given that tunnel overburden will exceed 2000m, temperatures as high as 45°C are projected. In addition, silicosis, an incurable disease of the lungs, caused by the unprotected respiration of quartz dust presents a p potential hazard to workers. Ventilation designs must g account for both factors to ensure worker safety.More than 13 million m3 of waste rockwill be generated, leading toenvironmental issues as to where toput it. At the same time, the it timeextraction of gravel resources forconcrete in the Swiss midlands isbecoming more difficult. The solution,therefore, was to specially break, sort& wash the waste rock so that it couldbe used for concrete aggregate. 44 of 46 Tunnelling Grad Class (2012) Dr. Erik Eberhardt 22
  • 23. Lecture ReferencesBaer, M, Deichmann, N, Braunmiller, J, Clinton, J, Husen, S, Fäh, D, Giardini, D, Kästli, F,Kradolfer, U & Wiemer, S (2007). Earthquakes in Switzerland and surrounding regions during2006. Swiss Journal of Geosci.ences, 100: 517–528.Bonzanigo, L (2007). Brittle tectonics in metamorphic rocks: Implications in the excavation of theBodio Section of the Gotthard Base Tunnel. In: Proceedings of the 1st Canada-US Rock MechanicsSymposium, VS i Vancouver. T l & F Taylor Francis: L d i London, vol. 2 pp. 1141 1148 l 2, 1141-1148.Ehrbar, H (2008). Gotthard Base Tunnel, Switzerland: Experiences with different tunnellingmethods. In: 2º Congresso Brasileiro de Túneis e Estruturas Subterrâneas Seminário Internacional“South American Tunnelling”.Ehrbar, H & Pfenninger, I (1999). Umsetzung der Geologie in technische Massnahmen imTavetscher, Zwischenmassiv Nord. In: Tagungsband Zum Sympoisums Geologie AlpTransit(GEAT99), Zurich. A.A. Balkema, Rotterdam, pp. 381-394.Fabbri, D (2004). The Gotthard-Base Tunnel: Project overview. In: 6th Annual TunnellingConference, Sydney.Hoek, E (2001). Big tunnels in bad rock: 2000 Terzaghi Lecture. ASCE Journal of Geotechnical andGeoenvironmental Engineering, 127(9): 726-740.Kaiser, PK, Diederichs, MS, Martin, D, Sharpe, J & Steiner, W (2000). Underground works inhard rock tunnelling and mining. In Proceedings, GeoEng2000, Melbourne. Technomic Publishing:Lancaster, pp. 841-926. 45 of 46 Tunnelling Grad Class (2012) Dr. Erik EberhardtLecture ReferencesLaws, S, Eberhardt, E, Loew, S & Descoeudres, F (2003). Geomechanical properties of shearzones in the Eastern Aar Massif, Switzerland and their implication on tunnelling. Rock Mechanicsand Rock Engineering, 36(4): 271-303.Loew, S, Ziegler, H-J & Keller, F (2000). AlpTransit: Engineering geology of the world’s longesttunnel system. In: Proceedings, GeoEng 2000, Melbourne. Technomic Publishing, Lancaster, 927–937.Zangerl, C, Eberhardt, E, Evans,Zangerl C Eberhardt E Evans KF & Loew S (2008) Consolidation settlements above deep Loew, (2008).tunnels in fractured crystalline rock: Part 2 – Numerical analysis of the Gotthard highway tunnelcase study. International Journal of Rock Mechanics and Mining Sciences, 45(8): 1211-1225.Zangerl, C, Loew, S & Eberhardt, E (2006). Structure, geometry and formation of brittlediscontinuities in anisotropic crystalline rocks of the Central Gotthard Massif, Switzerland. EclogaeGeologicae Helvetiae, 99(2): 271-290. 46 of 46 Tunnelling Grad Class (2012) Dr. Erik Eberhardt 23