1. Undersea Tunnel Construction
PF2302 Construction Technology
Undersea Tunnel Construction
Chao Chia Ling U086741H
Chen Chia 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)
Many different diameters ranging from microtunnel boring machine with diameter smaller than 1m to machine for large tunnels, whose diameters are greater than 15m
TBM are designed with specific diameter in order to cope with certain ground conditions.
For example, we can just refurbish the old machine with the same diameter but just redesign the cutterhead for different ground conditions.

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)
Many different diameters ranging from microtunnel boring machine with diameter smaller than 1m to machine for large tunnels, whose diameters are greater than 15m
TBM are designed with specific diameter in order to cope with certain ground conditions.
For example, we can just refurbish the old machine with the same diameter but just redesign the cutterhead for different ground conditions.

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):

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 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
To create two parallel rail tunnels, and a smaller service tunnel in between the rail tunnels

17. Construction details Soil characteristics: majority of chalk and clay
The tunnels were bored under seabed from both ends by TBM, sloping downwards
To create two parallel rail tunnels, and a smaller service tunnel in between the rail tunnels

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
Government’s plan
Location of the proposed tunnel

22. Overview
Government’s plan
Location of the proposed tunnel
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: Pasir Gudang Soft soil conditions
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: Radial 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
Solid rocks fall onto the bucket wheel and transfer to the conveyor-belt behind the cutting head
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
Cutter head with protruded
hard ground disc cutters
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
Conventional TBM is only preferred consistent ground conditions, require detailed site investigation and time-consuming
If change to a completely different machine during tunnel construction, additional investment and cost are required
May results in over-budget and delays

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

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
Fixed segmental lining to the surrounding soil, eliminate it from tearing down by push-in pressure

52. Lapping Joints & Tongue and Groove Joints
Water Stop
Plan View

53. Details of Waterproof Segmental Lining Joints

54. 5. Waterproof concrete lining joints
Special designed joints between each concrete segment
– lapping joints vs. tongue and groove joints
Reduce the need of grout in conventional concrete lining
Rubber water-stop encased and inserted between each concrete segment - enhance water tightness
Eliminate potential water seepage from high water-content soils

55. Improved TBM Improvements Reasons Strengths Limitations Probing
Difficulties in conducting soil investigation
Earlier soil detection
Small diameter probing
-reduce tendency of soil and water seepage
Reduce probability of disc cutter damages
Water seepage through probing holes
Adjustable Disc Cutters
Homogeneous soil characteristics are preferred in conventional TBM
Able to cater different types of soil
Less disc cutter wear, expand the disc cutters life duration
Reduce the tendency of regular maintenance and inspection on disc cutters
Reduce time in obtaining comprehensive site investigation
Reduce additional cost arising from modification of machine
High cost in programming and maintenance

56. Improved TBM Improvements Reasons Strengths Limitations Spray Cement
Pneumatic Hoses
High Water Pressure
Permeable Soils
Push-in Pressure
A layer of water-proofing protection to TBM shield
Prevent soil collapse from high water content and push-in pressures
Increase stiffness and strength of surrounding soil
Seawater effect
Cost for materials
Ground Anchors & Grouting
High water content
Soil Movement
Seismic & Tremor
Control surrounding ground movement
Reduce the permeability of the ground
Prevent concrete lining deformation
Increase load resistance
Enhance bond strength between segmental concrete lining and surrounding soil
Expensive construction cost

57. Improved TBM Improvements Reasons Strengths Limitations
Waterproof Concrete Lining
Joints
High water seepage between concrete lining joints – Insufficient conventional butt joint
Hydrostatic Pressure
Enhance water tightness
Prevent Water Seepage
Reduce the need of grouting on concrete lining NA

58. Conclusion

59. Conclusion Reasons of choosing us:
Past experiences in Channel Tunnel, an under seabed tunnel construction
5 proposed improvements of the existing TBM method in this project

60. Conclusion Suggestion of enhancing the performance of improved TBM:
Providing detailed geotechnical data of the project by LTA and Malaysia government
Working with detailed site investigation team

61. References:
Channel Tunnel TBM Back-up System
Mega Engineering: Tunnel Under the Sea
Case study – Channel tunnel Rail link

62. Thank You