G5_Group-Presentation of tunneling module.pptx

it is the presentation on different methods of tunneling

1. Special Methods of Tunnelling -uses of tunnel boring machine (TBM) Group 5: Namgay Lhaden Kuenzang Dema Kinzang Choden Nima Tamang Yonten Thinley

2. Outline Special methods of Tunnelling New Austrian Tunneling Method (NATM) or Sequential Excavation Method (SEM) Cut and Cover Method Immersed Tunnel Jacking method Uses of TBMs 2

3. 1 . NATM/ SEM The New Austrian Tunneling Method (NATM) or Sequential Excavation Method (SEM) can be defined as a support method to stabilize the tunnel perimeter with the help of sprayed concrete, anchors and other support and uses regular monitoring to control stability of the tunnel (Ahmad et al., 2019). It was Rabcewicz in 1948 who patented the very idea of this tunneling method (Schubert,2015). NATM is best suited for short-range (> 2 km) tunnels in regions with variable soil conditions. Its philosophy and construction method yield a more cost-effective, flexible tunneling operation when compared with the other methods. 3

4. NATM is based on the following principles of : Prevention from disintegrating of rock mass, hence keeping its strength. Rock mass classification. Shotcrete protection Monitoring the behaviour Construction measures Advantages of NATM: Adaptability: adapts to varying geological conditions, making it highly flexible for different environments, especially in complex terrains. Faster Construction: use of shotcrete for immediate stabilization allows for faster progress in tunnel excavation compared to more traditional methods. Minimal Environmental Impact: causes less disturbance to the surrounding environment and structures, making it suitable for urban tunneling projects. Improved Safety: monitoring allows for early detection of potential hazards, leading to safer working conditions in potentially unstable ground. 4

5. Sequence of NATM: Profile Marking : Marking the tunnel alignment on the ground for accurate excavation. Face Drilling : Drilling holes into the rock face for controlled blasting. Charging and Blasting : Filling holes with explosives and detonating them to break rock. Defuming : Ventilating the tunnel to remove harmful gases and dust post-blasting. Mucking : Removing loose rock and debris from the tunnel using specialized machinery. Scaling (if needed): Removing loose rock from walls to enhance safety. Geological Face Mapping : Analyzing the rock face to assess conditions for construction methods. 5

6. 8. Face Sealing Shotcrete : Applying a thin shotcrete layer for immediate stabilization. 9. Lattice Girder Erection : Installing girders to support the tunnel roof. 10. Fore Poling (if needed): Placing poles ahead of the tunnel face for temporary support in weak ground. 11. 3D Monitoring : Installing points to track tunnel deformation and ground movement. 12. Initial Lining Shotcrete : Applying a thicker shotcrete layer for long-term stability. 13. Rock Bolting & Grouting : Installing bolts and injecting grout to reinforce the rock mass and tunnel. 6

7. Fig 1: Sequence of NATM. Source: (Ahmad et al.,2019) 7

8. Limitations of NATM/ SEM: Geological Uncertainty : Unpredictable conditions can cause delays or require extra reinforcements. High Initial Investment : Monitoring equipment and skilled labor setup can be costly. Over-reliance on Monitoring : Inaccurate monitoring can misjudge ground conditions, risking instability. Limited in Poor Ground : Less effective in weak or fractured ground with insufficient support. Time-Consuming Adjustments : Frequent adjustments based on monitoring can delay the project. 8

9. 2. Cut and Cover The Cut and Cover method in tunnelling is a construction technique used for building shallow tunnels. There are two C and C techniques. The “Cut and Cover” and “Cover and Cut” methods are advanced engineering techniques for tunnel construction in urban and interurban areas . Figure 2. “Cut and Cover” tunnel. 9

10. C&C Techniques Aspect Cut and Cover Cover and Cut Depth Limited depth (<50m) Shallow overburden Use Case Sensitive areas, temporary relocation of utilities Highly sensitive areas, utilities can't be relocated Geotechnical Conditions Used in adverse conditions (faults, loose materials) Minimizes excavation risk Environmental Impact Moderate impact Lower impact due to shallow grading Excavation Risk Higher risk than "Cover and Cut" Lower excavation risk 10

11. Figure 3. Stages of Construction for the “C&C Techniques (cut and cover on left, cover and cut on right) The “ Cut and Cover ” method is preferred to the traditional open excavation leading to cutting sections for reasons of environmental protection and geotechnical stability . 11

12. 1. Site Preparation : Clear the area and relocate utilities. 2. Excavation : Dig a trench to the required depth. 3. Support Installation : Install temporary supports to prevent trench collapse. 4. Tunnel Construction : Build the tunnel structure (usually Precast-concrete) inside the trench. 5. Utility Installation : Install utilities (drainage, lighting, etc.) within the tunnel. 6. Backfilling : Fill the trench with compacted soil and restore the surface. 7. Final Touches : Complete entrances, exits, and remaining finishes. Procedure of Cut and Cover method 12

13. Cut and Cover in Soft soil and Rock Formation Aspect Cut and Cover in Soft Soil Cut and Cover in Rock Formation Soil Conditions Involves soft, unstable soils requiring immediate support systems. Involves various grades of rock, typically medium hard to very weak. Support Systems - Soil nail walls - Anchored retaining walls (panel or column type) - Sheet piles - Micro piles - Braced excavations - Rock bolts Excavation Methods - Excavators (backhoes, bucket loaders) - Drill-and-blast methods - Dump trucks for soil removal - Hydraulic hammer excavation   - Diamond wire saws Ground Stability Requires ground strengthening to prevent collapse during excavation. More stable than soft soil; usually does not require ground strengthening. Construction Techniques - Backfilling - Shotcrete for surface stabilization - Drainage management - Grouting for rock improvement Material Handling - Compactors and rollers for soil compaction - Rock trucks for transporting excavated materials - Dump trucks for backfill - Crushers for breaking down rock Quality Control - Soil testing equipment for monitoring stability - Geotechnical instruments for monitoring ground stability 13

14. Limitation of Cut and Cover method Surface Disruption : Extensive excavation affects traffic and local communities. Ground Stability : High risk of soil collapse in soft conditions, requiring complex support. Utility Interference : Existing underground utilities often need temporary relocation. Depth Limitations : Effectiveness decreases significantly with greater depths. 14

15. 3 . Immersed Tunnels Immersed tunnels are prefabricated tunnel sections placed underwater, typically used to cross shallow bodies of water ( Kuensel et al., 2012). They provide a transportation link in areas where bored tunnels or bridges may be impractical. Figure 4 : Image of an immersed tunnel.

16. Types of immersed tunnel 1. S inge-shell steel tunnel 2. Double-shell steel tunnel 3. Sandwich construction tunnel 4. Concrete-Immersed tunnels Figure 5. Types of immersed tunnels ( Sciencedirect , 2018) 16

17. Construction Method Trench Excavation : The first step involves excavating a trench along the path where the tunnel will be placed. This trench is typically dug in the seabed, using specialized dredging equipment (Clamshell dredgers). Foundation Preparation : The trench needs a stable base to support the heavy tunnel elements and prevent settlement after installation. Using sand injection or grout injections to stabilize the base (Zhou et al., 2021). Fabrication of Tunnel Elements : The tunnel sections are typically prefabricated at a dry dock or shipyard, far from the installation site. Figure 6. Clamshell Dredgers Figure 8. Installation of a continuous rubber gasket Figure 7. Sand injection 17

18. Construction Method Transportation & Lowering : Once the tunnel sections are constructed, they are floated to the installation site using pontoons or tugboats. Alignment & Connection : Once a tunnel section is in place, it must be aligned with the previous section with a high degree of precision. Misalignment can lead to leaks or structural problems later on. Backfilling : Backfilling is done to secure the tunnel sections in place and provide additional support and protection from external forces such as water currents or earthquakes. Fig ure 9.Tunnel elements in transportation. 18

19. Advantages Immersed tunnels can be designed to accommodate a wide range of cross-sections, allowing for versatility in their use. Immersed tunnels can support larger cross-sections than bored tunnels, which is crucial for busy transportation corridors. As long as the seabed is reasonably stable, these tunnels can be constructed with minimal disruption, making them suitable for coastal and river crossings in a variety of geological settings. Limitations During the transportation and placement of tunnel sections, marine traffic is often disrupted. It is sensitive to Ground Conditions. The trench must be stable enough to support the tunnel sections without shifting or collapsing. Location Challenges 19

20. Real life Examples Oresund Tunnel (Denmark-Sweden) Part of the Øresund bridge and tunnel connection, crossing shallow water (Hedberg, 2002). which connects Denmark and Sweden via both a bridge and a tunnel. Hong Kong-Zhuhai-Macau Bridge Tunnel One of the longest undersea tunnels in the world ( Quanke et al., 2022). This tunnel is part of the Hong Kong-Zhuhai-Macau Bridge, a massive infrastructure project that connects Hong Kong, Macau, and Zhuhai. Busan- Geoje Fixed Link (South Korea) Connects Busan to Geoje Island with an immersed tunnel section. connects Busan, South Korea’s second-largest city, to the island of  Geoje . Figure 10. Oresund Tunnel Figure 11. Hong Kong-Zhuhai-Macau Bridge Tunnel Source: Sciencedirect Source: Sciencedirect Figure 12. Busan-Geoje Fixed Link S ource: Engineering new records 20

21. 4.Pipe jacking method Pipe jacking (also called microtunnelling) is a micro to small-scale tunneling method used to install utility tunnels and conduits by thrusting pipes through the ground as controlled excavation is undertaken at the face. It is used mostly for smaller diameter tunnels and in urban areas. Pipes are pushed through the ground behind the shield using powerful jacks. Simultaneously excavation takes place within the shield. This process is continued until the pipeline is completed. Figure 13. Pipe jacking in tunneling (Sterling, 2018) 21

22. Pipe-jacking method consists of jacking segmental pipes by means of a tunnel boring machine (TBM) and hydraulic jacks to complete an underground pipeline network. Pipe jacking involves pushing pipes from a starting point (launch shaft) to an ending point (reception shaft). Hydraulic jacks in the launch shaft provide the force to move the pipes forward. A machine at the front, like a shield or tunnel boring machine (TBM), controls the digging process. As the machine moves forward, the jacks push the pipes behind it, creating the tunnel. Figure 14. Pipe jacking process (a) Jacks pushing pipe (b) General layout of pipe jacking a) b) 22

23. Equipment and components: Hydraulic Jacks : Provides the pushing force for pipe segments. Jacking Pipes: Precast pipes made of materials like concrete, steel, or polyethylene that is push into place Cutting Head or Shield : Positioned in front of jacking pipe. It cuts down the soil ahead using mechanical motion into smaller fragments. Thrust Ring Thrust ring distributes force from jack head to pipe edges equally. A spacer is optional. Spoil Removal Systems : Augers, conveyors, or slurry systems to transport excavated materials out of the tunnel. Fig: Jack Figure 15. Pipes 23

24. Thrust wall: Thrust wall is provided behind the jack to transfer back thrust of jack to earth and preventing jack to sink. Intermediate Jack : Intermediate jack is provided in between the entry and exit shaft. Number of intermediate jack depends on pipe length and jack capacity. Intermediate jack must match pipe diameter Boring Machines (TBM) : Sometimes used for larger tunnels to excavate the soil in front of the pipe . Figure 16 : Intermediate Jack Figure 19: Cutter-head Figure 17: Thrust Ring Figure 18:Thrust Wall 24

25. Advantages of Pipe Jacking: Minimal Surface Disruption : No need for continuous open trenches, making it ideal for urban environments. Precise Alignment : The use of guided systems or TBMs ensures accuracy in tunnel positioning. Environmental Benefits : Less excavation means lower environmental impact. Versatility : Can be used for a variety of underground utilities and across different ground conditions. Applications of pipe jacking: Sewers, and drainage construction Industrial pipelines. Gas and water mains Telecommunication. Oil pipelines. Pedestrian subways (access tunnels). 25

26. Uses of TBM in Underground Transport and Structures TBMs prevent surface disruptions, essential in dense urban areas like subway, road, and utility tunnels. Reduces the risk of collapsing tunnels, crucial in cities with existing structures. Underwater transport systems can be constructed safely and effectively using the TBMs. TBMs offer highly controlled and precise excavation. For long straight underground railway, TBMs is cost effective and time efficient method ( Munfah , 2019). 26

27. TBM in Mining TBM is also used in mine development, primary for development of entries, ventilation, haulage and production drifts. TBMs create stable and long tunnels quickly for material transport and access, enhancing safety and efficiency. Use of TBM in mining dates back in early 50s ( Cigla et al, 2001). Where penetration rates were far above drill and blast, however it faced many challenges and hardships. Development of TBM specially suited for mining increased the successful application in field of mining. Examples: San Manual Mine (Magma copper company) and Stillwater platinum mine in US. 27

28. TBMs in Hydropower Handle large-diameter, long tunnels needed in water diversion, penstock tunnels, and hydroelectric projects ( Grandori , 2007) . TBMs minimizes surface disruptions in environmentally sensitive areas preserving landscapes, ecosystems and reduces environmental impacts. TBMs can bore long tunnels quickly, reducing construction time. Provides immediate tunnel support, reducing risks of collapse and improving worker safety. 28

29. Uses of TBMs in Difficult Geological Conditions TBMs can be used for various geological conditions; Earth Pressure Balance (EPB) TBMs Most suited for soft soil and mixed ground with lower moisture content (Robbins, 2021). Slurry TBMs Used in loose water logged conditions and handles water pressure effectively. Hard rock TBMs Equipped with heavy duty cutters capable to breakthrough the hard rocks. Mixshield TBMs Uses a pressurized slurry system to manage unstable ground and high water inflow. 29

30. Summary Higher advancing rate Safety and structural integrity Uniform muck production Efficient and continuous excavation Minimal environmental impact Versatility 30 Figure 20: Tunnelling Boring Machine.

31. References Ahmad, Aejaz , et al. New Austrian Tunneling Method (NATM) in sHimalayan Geology: Emphasis on Execution Cycle Methodology. June 2019. Cigla , M., Yagiz , S., & Ozdemir , L. (2001). Application of tunnel boring machines in underground mine development . https://www.semanticscholar.org/paper/Application-of-Tunnel-Boring-Machines-in-Mine-Cigla-Yagiz/c620f86a29893499ebbbb50a0ed799626f286445 Grandori , R. (2007). Tunnel construction in hydro projects: The use of TBMs. ResearchGate . https://www.researchgate.net/publication/295567382_Tunnel_construction_in_hydro_projects_The_use_of_TBMs Hedberg, T. (2002). Øresund Fixed Link, Denmark and Sweden.  Structural Engineering International ,  12 (4), 239–241. https://doi.org/10.2749/101686602777965171 31

32. Kuesel , T. R., King, E. H., & Bickel, J. O. (2012).  Tunnel Engineering Handbook . Springer Science & Business Media. Munfah , N. (2019, June 10). Advancing in Tunnelling overcome challenges in Urban Areas. Tunnel Business Magazine. https://tunnelingonline.com/advances-in tunneling -overcome- challenges-in-urban-areas/ Quanke , S., Yongling , Z., Yue, C., Lei, F., Yu, Y., Zongxian , S., de Wit, H., & Ying, L. (2022). Hong Kong Zhuhai Macao Bridge-Tunnel project immersed tunnel and artificial islands – From an Owners’ perspective.  Tunnelling and Underground Space Technology ,  121 , 104308. https://doi.org/10.1016/j.tust.2021.104308 Robbins. (2021, October 24). Earth Pressure Balance - Robbins . https://www.robbinstbm.com/products/tunnel-boring-machines/earth- pressure- balance/ 32

33. Sehgal, D. (2016, April 30). Cut and cover [Slide show]. SlideShare. http://www.slideshare.net/DheerajSehgal1/cut-and-cover Schubert w, Development and Background of NATM, Austrian Tunnelling Seminar Ankara, Austrian Society for Geomechanics, March 31st & April 1st, 2015. Zhou, M., Su , X., Chen, Y., & An, L. (2021). New Technologies and Challenges in the Construction of the Immersed Tube Tunnel of the Hong Kong-Zhuhai-Macao Link.  Structural Engineering International , 1–10. https://doi.org/10.1080/10168664.2021.1904487 33

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