Undersea Tunnel Construction: TBM Technology & Techniques

1. PF2302 Construction Technology Undersea Tunnel Construction Chao Chia Ling U086741H Chen Chia Wei @ Nay Zar Aung U097945R Chia Kim Hong U097944E Chu Phuong Linh U097921A Jacqueline Huan Chie Sze U086743E Le Thuy Linh U097917B

2. Scenario of Presentation: • Tendering for the TBM construction of undersea tunnel of the third link between Singapore and Johore • We are contractor of Tunnel Boring Machine (TBM) company • Past experience in Channel Tunnel construction • Professor Chew is LTA • Who offers the contract of completion and construction of undersea tunnel

3. CONTENTS • Introduction of Tunnel Boring Machine (TBM) • Past Experience in Tunnelling - Channel Tunnel • Punggol – Pasir Gudang Tunnel • Competitive points in winning the tender • Improvements on TBM • Improvements in tunnel stability • Conclusion

4. Introduction of TBM

5. What is Tunnel Boring Machine? • Tunnel boring machines (TBM) are used as an alternative to drilling and blasting (D&B) methods in rock and conventional 'hand mining' in soil • A machine used to excavate tunnels with a circular cross section (different diameters ranging from 1m to 19m) • Able to drill horizontally through many different geological and ground conditions (variety of soil and rock strata)

6. Types of Tunnel Boring Machine • Tunnel Boring Machine in hard rocks – Gripper TBM, Shield TBM • Tunnel Boring Machine in soft ground – Slurry Tunnelling Machines, Earth Pressure Balance Machines (EPBM)

7. Construction sequences of Tunnel Boring Machine • Excavation or construction of launching shaft (Cut-and-cover method, top-down method, diaphragm wall method) • Assembly of TBM • Support of undercut and tail tunnel • Excavation of tunnel itself • Disposal of soil from tunnel face • Hoisting the soil to ground level

8. Construction sequences of TBM • Lining the tunnel • Installation of rail track, ventilation, electrical and other cables • Excavation or construction of receiving shaft • Disassemble TBM • Close of launching and receiving shaft upon completion

9. Construction sequences of TBM • Details process (Excavation, Support, Reinforcement, Concreting and Lining of Tunnelling): • http://www.youtube.com/watch?v=n0BCT4lJsX0

11. Advantages of TBM • Minimal ground disturbances • Minimal support requirements • Continuous mining, non-cyclical progress • No explosives, reduce changes of rock fallings • Improved workplace safety • Producing a smooth tunnel wall • Reduces the cost of lining the tunnel

12. Disadvantages of TBM • Cost – Expensive to construct • Problems for cutter heads – Difficulties in hard, abrasive, weathered, sheared, highly jointed rocks • Limitation for changing rock conditions - Unable to change cutter during construction stage • Limitation in the modification of the machine • Circular profile results in over-excavation • Insufficient waterproofing for conventional segmental lining joints – Water Seepage

13. Channel Tunnel

14. Background • Pass below the English Channel and connects England and France • Total length: 50 km • Average of 40m under seabed • One of the longest tunnels in the world

15. Background • Construction began in 1984 and completed in 1993. Opened in 1994 • The tunnel is for use of train

16. Construction details • Three tunnels involved • Two tunnels for trains • The middle one is for maintenance and emergency escape route

17. Construction details • Soil characteristics: majority of chalk and clay • The tunnels were bored under seabed from both ends by TBM, sloping downwards

18. Construction details • High density concrete sprayed to prevent sea water • Air is supplied for ventilation • A massive air filtering system to ensure no harmful fumes build up

19. Construction details • Five massive pumping stations located at either ends and three under the sea • Machines continued boring until close enough to use air powered drills to connect the two sides • Service tunnel then connected with main tunnels by drilling and blasting

20. Punggol – Pasir Gudang Tunnel

21. Overview • Punggol – Pasir Gudang • Length: 3.8km • Lowest depth: 61m under sea level • Method: Tunnel Boring Machine of 7m diameter (TBM) • Gradient ratio 1.2% • Completion time: 3 years

22. Overview Not to scale

23. Problems encountered • Soil characteristics • Significant seepage gradient and permeability of soil • Inaccuracy of underwater geological investigation • Seismic factors • High water pressure over long term • Environmental issues • Ventilation and lighting

24. Soil characteristics • In Singapore: Punggol • Undeveloped landscape not disturbed by housings and construction wastes • Sahajat formation: quartzite, quart sandstone and argillite • Old Alluvium: gravel, sand, silt and clay • Both soft and hard soil conditions

25. Soil characteristics • In Malaysia: PasirGudang • Industrial zone  high density of plants and factories and transportation • Not many high rise building  not affected by deep foundations • Unconsolidated deposits: clay, silt, sand and gravel  soft soil condition • Soft soil conditions

26. Soil characteristics • Offshore (Under seabed soil) • Lack of information • Site investigation under the seabed is costly and inaccurate • Expected to be similar to soil condition onshore • Upon approval • More detailed investigations will be done • Use of probing during construction

27. Significant seepage gradient and permeability of soil • Punggol near two estuaries  High seepage gradient level • High permeability soil characteristics  Need more considerations in grouting and soil improvement • Significant water content & water leakage  Need waterproofing precautions

28. Inaccuracy of geological investigation • Less accuracy of underwater geological investigation • Due to depth of the seabed • Current technology cannot adequately support underwater geological information that required for construction • Unexpected geological features, such as faults or disturbed zones  Use of probing as the tunnel goes

29. Seismic Factor • Singapore - Malaysia seismic profile: • Not located in Earthquake zones • Near Earthquake zone (eg. Indonesia) • Experience light tremors • Soil condition: Generally soft • Allow unexpected movements for the tunnel • Shear force induced during occurrence tremors  Apply grouting along the tunnel, especially at critical zone

30. High water pressure over long term • Pore water pressure • The groundwater creates the pore water pressure. • Soil characteristics lead to high pore water pressure and water leakage • Reduce the stability of soil • Arch the tunnel Solutions: grouting and cement spraying

31. High water pressure over long term • Hydrostatic pressure • Overburden above the tunnel • The pressure exerted affects the loading on the liners • Break of concrete lining • Soil collapse Solution: Cement spraying, drainage and water-proofing

32. Environmental issues • More eco-friendly than a cofferdam causeway • Needs: • Not affect the sediments of Quaternary age • Vibration during construction=> required depth of 30m • No change in the surrounding groundwater levels and water chemistry • Not affect the undersea ecology

33. Improved TBM

34. Competitive Points in Winning the Tender • Improvements on Tunnel Boring Machine • Soil Characteristics Detection - Probe Drilling • Flexible and adjustable disc cutters • Spray cement pneumatic hoses • Improvements in Tunnel Stability • 4. Concrete lining with ground anchors and grouting • 5. Waterproof concrete lining joints

36. 1. Probe Drilling • Reason for use of probing: lack of geological information offshore • Two types of probing are used: • Advanced probing ahead of the tunnel • Radial probing vertically from the tunnel surface

37. Probe Drilling • Advanced probing: • Dual probes • 150m long • Inclination 2° - 4° • Diameter 35mm • Radial probing • One vertically upwards • One vertically downwards • 200m long • Diameter 35mm

38. Probe Drilling • Earlier soil detection • Small diameter probing • - reduce tendency of soil and water seepage • Reduce probability of disc cutter damages

40. 2. Flexible and adjustable disc cutters Cutter head with alternatively protruded soft and hard ground disc cutters

41. Bucket Wheel Conveyor Belt Distribution of Disc Cutters

42. Adjustable Disc Cutters Sealed disc cutter Protruded disc cutter Hydraulic Jacks Movable hydraulic jack Fixed end

43. Adjustable Disc Cutters • Able to cater different types of soil • Less disc cutter wear, prevent early breakage of disc cutters and expand the disc cutters life duration • Reduce maintenance and inspection frequency on disc cutters • Reduce time in obtaining comprehensive site investigation • Reduce additional cost arising from modification of machine Cutter head with protruded soft ground disc cutters Cutter head with protruded hard ground disc cutters

45. 3. Spray cement pneumatic hoses Original TBM with extra chamber/space in the shield Improved TBM with spray cement jacking pipe installation in the extra chamber/space

46. 3. Spray cement pneumatic hoses • A layer of water-proofing protection to TBM shield • Prevent soil collapse from high water content and push-in pressures • Enhance the ability of undertaking overburden loads

48. Ground Anchors-Corrugated UPVC Ducts with Tendons Grouting-Expansion Bulb 4. Concrete lining with ground anchors and grouting

49. 4. Concrete lining with ground anchors and grouting • Control surrounding ground movement • Prevent concrete lining deformation • Increase load resistance • Densification the surrounding soils and reduce the permeability of the ground • Enhance bond strength between segmental concrete lining and surrounding soil