1. Selection Criteria for Tunnel Construction
Building on Our Growth Opportunities May 27 – 30, 2015
Miser sur nos opportunités de croissance REGINA, SK
Selection Criteria for Tunnel Construction
Mohamed Darwish, PhD, PEng
Reem Aboali
Osama Hashem
Shady Girgis
Menna Amr assal
Amira Saied Youssef
Mohamed Auf
Aya Diab
Mireille Kirolos
Mohamed Seif
Yousef Shehata
Presented by:
Reem Aboali

2. Introduction
Tunnels
Mining
Transportation and sanitary purposes allover the world
Construction of tunnels involves utilizing unique construction methods due to various characteristics like cost, constructability, resources & time.
Tunnels are necessary for mining, transportation and sanitary purposes allover the world. Construction of tunnels involves utilizing unique construction methods due to various characteristics like cost, constructability, resources and time. different methods of tunnel construction by concentrating on different construction methods of every type of tunnels. Moreover, a comparative analysis is provided to show when to use every method of construction according to the conditions available. Two projects involving tunnels with different sizes and project conditions were studied and examined against the developed selection criteria in order to evaluate the validity of the applied construction methods in each case

3. Trenched Method- Cut & Cover
A shallow place (10-12 m)
Economical
Practical & easier in construction
May cause traffic problems, noise & dust
Not Economical if >12 m/dewatering
The trenched cut and cover tunnels are usually built through excavations and then covered in backfill material when it is done. It is usually used for tunnels that are needed in a shallow (within 10 to 12 m) place where excavation is easier and possible as it can be also economical. It is designed in a form of a rigid box and the quality and finishes is according to the area whether it is open urban areas or space limited areas. This tunneling method is economical, practical and easier in construction than most tunneling technologies. However, if the tunnel is underneath a city street it will cause traffic problems, dust and noise and if it is deeper than 12 meters it will not be economical any more. This method is mainly used when there is no need for restoration for the ground surface, if there is enough space in the construction process, if it will not affect traffic and if there is no need to emphasis on the sidewall deflection

4. Trenched Method- Cut & Cover
Bottom Up Method
Structurally independent of the support walls
Top Down Method
Side support walls, main contributor in the tunnel structural system
The trenched cut and cover tunnels are usually built through excavations and then covered in backfill material when it is done. It is usually used for tunnels that are needed in a shallow (within 10 to 12 m) place where excavation is easier and possible as it can be also economical. It is designed in a form of a rigid box and the quality and finishes is according to the area whether it is open urban areas or space limited areas. This tunneling method is economical, practical and easier in construction than most tunneling technologies. However, if the tunnel is underneath a city street it will cause traffic problems, dust and noise and if it is deeper than 12 meters it will not be economical any more. This method is mainly used when there is no need for restoration for the ground surface, if there is enough space in the construction process, if it will not affect traffic and if there is no need to emphasis on the sidewall deflection

5. Immersed Tunneling
More feasible & efficient technique for a tunnel crossing a waterway
Application is function of :
Good weather
Reasonable water currents
Sufficient bearing capacity for riverbed/seabed
Constructing a tunnel crossing a waterway is a task that could consume a lot of time and resources if done by boring or jacking technologies, a more feasible and efficient technique is to immerse the tunnel and let it rest on the seabed/riverbed. On deeper tunnels, it is preferable to minimize diver operations due to the greater risk at depth. In some cases diving bells are used, in other cases robotics could be used. Of course the application of such method is function of having good weather conditions, reasonable water currents and a riverbed/seabed of a sufficient bearing capacity. If one or more of these factors is absent it may force the use of other trenchless methods

6. Immersed Tunneling
More feasible & efficient technique for a tunnel crossing a waterway
Application is function of :
Good weather,
Reasonable water currents
Sufficient bearing capacity for riverbed/seabed
Constructing a tunnel crossing a waterway is a task that could consume a lot of time and resources if done by boring or jacking technologies, a more feasible and efficient technique is to immerse the tunnel and let it rest on the seabed/riverbed. On deeper tunnels, it is preferable to minimize diver operations due to the greater risk at depth. In some cases diving bells are used, in other cases robotics could be used. Of course the application of such method is function of having good weather conditions, reasonable water currents and a riverbed/seabed of a sufficient bearing capacity. If one or more of these factors is absent it may force the use of other trenchless methods

7. Tunnel Boring
Competent rocks that provide adequate geological stability for boring a long section tunnel without structural support.
Excavation is done by Tunnel Boring Machines (TBM's).
Used for tunneling under bodies of water.
Involves digging a tube-like passage through the earth.
Capital intensive with high mobilization costs.
Long tunnels construction.
Rather than conventional tunneling methods which extensively use explosives and manual labor, mechanized tunnel
Usually used in
Suitable for excavating tunnels which contain

8. Earth Pressure Balance (EPB)
Tunnel Boring
Average Production Rate: 5-10 m/day
Tunnel Boring Machine (TBM) Length: 100 –150 m
Diameter:
1 – 14.4 m(Hard Rock TBM)
1 – m (Soft Ground TBM)
TBM
Hard Rock TBM
Shielded
Open type
Soft Ground TBM
Earth Pressure Balance (EPB)
Slurry Shield (SS)
Open Face Type
Typical TBM can excavate

9. Hard Rock TBMs Open Type TBM: Shielded TBM:
No shield, area behind cutter open for rock support.
Advances using gripper system
Support systems instead of concrete segments
Shielded TBM:
Used with fractured rock, erecting concrete segments to support unstable tunnel walls behind the machine.
Could be single-shielded or double- shielded

10. Soft Ground TBMs Earth Pressure Balance (EPB):
Mixes excavated soil, foaming agents, water and polymers in the working chamber behind cutter head. The muck pressure is controlled by the pressure wall.
Screw conveyor takes the mud out of the machine as the machine moves forward.
Slurry Shield (SS):
The cutter head is balanced by bentonite slurry.
Screw conveyor is replaced by two pipes circulating the slurry in and out of the working chamber.
SS: Same concept of the EPB however,

11. Multi-mode (Mixshield) TBMs
Developments were done to include changing modes of operation as follows:
Changing modes of operation between open face single shield and closed EPB shield
Changing modes of operation between closed slurry shield and open face single shield
Changing modes of operation between EPB and SS modes.
Such costly developments broaden the type of soil that could be bored within a single project reducing the risks of stopping the excavation due to soil type change

12. TBM Selection Criteria
Ground type
TBM type
Suitable Ground Condition
Cost
Speed
Risks
Soft Ground
EPB
Water head< 4 bars & fine materials> 10%
High
Moderate
Low SS
Permeability from 10−8 to 10−2 m/s
Open face
weak rock, fully/partially cohesive soils with low GWT
Multi-mode TBM’s
Most of soil types
Highest
Variable
Hard Rock
Unshielded
Rock compressive strength from 100 to 300 MPa
Single-shield
Rock compressive strength from 50 to 300 MPa
Double-shield
Lowest

13. Jacked Box Tunneling
Prefabricated tunnel sections pushed one after the other by hydraulic jacks
Jacked tunnel progress: 1-2 m/day
The maximum recorded rate : 4m /day
Lower vibration & disturbance to the surrounding soils & structures
Commonly used to
cross tunnel beneath railways
Underground structure & tunnels
Within this trenchless method of construction, tunnel sections are prefabricated and then are pushed one after the other by hydraulic jacks. In this method, the tunnel concrete section is completely constructed on one end of the tunnel and placed in the jacking pit that is excavated at one end of the tunnel

14. Drill & Blast Method Step 1: Drilling holes & uploading explosives
Holes are drilled in s apecific pattern to produce the most economic & satsifactory brekage of rocks
Step 1: Drilling holes & uploading explosives
Step 2: Blasting & ventilation
Step 3: Mucking, broken rock/ earth
Step 4: Smoothing out the surface of the blasted rock

15. Drill & Blast Method Merits: Waste materials generated would be less.
Disturbance to local traffic & environmental impacts would be much reduced
Blasting significantly reduce the duration of vibration
Drawbacks:
Safety risks for workers.
Fumes and gases generated from detonating explosives are toxic
Noise pollution generated from blasting
Blasting fracture the rock around the tunnels/ uncontrolled rockslides/falling debris
quantity of waste materials generated would be much reduced.

16. Sequential Excavation Method
New Austrian Tunneling Method ( NATM)
Utilizing the self supporting capability of the ground hence achieving an economically sound ground system
Used with dry soil where roads are used for excavation

17. Sequential Excavation Method
Support element is shotcreting, providing interlocking & continuous support to the ground
SEM is slower than TBM constructing long tunnels

18. Trenchless Methods Selection Criteria
TBM
Jacked Box
Drill-and-blast
SEM
Immersed
Suitable Soil Type
Various Soils
Soft grounds
Rocks
Rock and cohesive soils
Requires high bearing capacity
Cost
Cost saving for long tunnels
Cost saving for short tunnels
Cost efficient
Level of Mechanization
Highly mechanized
Moderately mechanized
Constructability
Soil dependent
Moderate
Depends on project conditions
Productivity
High
Low
Highest
Mobilization Time
Long
Short
Construction Risk
Project dependent
Weather dependent
Safety
Depends on machine type
Safe
Least safe
Most Suitable Location
Long Tunnels
Short tunnels beneath/beside structures
Short in-the-rock tunnels
Short tunnels, large openings, complex shapes
Water crossings
A selection criteria were developed to evaluate the validity of the applied construction method

19. Case Study#1: Boston Big Dig, Boston, USA
Objective: Replace deteriorating 6-lane elevated highway to 8-10 lane underground including construction of Ted Williams Tunnel ( Interstate 90 – Logan International Airport)
Cost: $ 14.6 billion
Duration 20 years
The project was almost the most expensive highway constructeed in the US with a cost and was completed after

20. Boston Big Dig, Boston, USA
I-90: Ted Williams Tunnel
Coastal Section (1)
Bottom-uo open cut trench
Boston Big Dig, Boston, USA
I-90: Ted Williams Tunnel
Coastal Section (1)
Bottom-up open cut trench
As for the applied method , the Ted Williams Tunnel consisted of two sections te coastal section & the underwater section

21. Boston Big Dig, Boston, USA
I-90: Ted Williams Tunnel
Under-water Section ( Immersed Tunneling)
Steel Sections from Baltimore
Cast in place concrete sections
The underwater sections contained two sections.Those sections were desgined to float on the water surface & contained empty commpartmentd that were flooded by water to sink the section after reaching the poistion of thr section floating

22. Boston Big Dig, Boston, USA
I-90: Fort Point Tunnel
Piles were driven at the two sides of the metro to load it on lower bed rock
Ted williams including the construction of two different tunnels. The for point tunnel wias one of the most challenging as it was few points above metro linePiles were drived at the two sides of the metro to load the tunnel on the lower bed rocksinteasd of loading the tunnel on the soil above the metrp

23. Boston Big Dig, Boston, USA
I-90: Tunneling under Railway Network
Boston is constructed over Landfill composed of blue clay
Solidify soil by ground freezing
The samller section of this tunnel passes under the railyway. The tunneling should casue minimal disturbances under the rail to avoit the deraliment of the trains. The main problems was that Boston is mainly constructed over landfill composed of landfill composed of blue clay. To solve this problem , gorund freezing was appliued to soldify the soil and make it holde itself during the digging process

24. Boston Big Dig, Boston, USA
I-90: Tunnel Jacking
The tunnel concrete was completely constrcuted on one end of the tunnel & equipment were used to excavate the soil in front of the tunnel section
Moreover, the box jacking method of construction was used to enusre tha tains safety. In this method, the tunnel concrete was completely constructed on one end of the tunnel, then equoment wrere used to excvatae the soul infront of the tunnel section.

25. Case Study 1: Method Evaluation
Using a cut-and-cover in the first section: most economic. Trenchless technique in that location would have been a waste of money.
For the two under-water sections, the usage of the immersed tunneling technique was the optimum solution as the weather and water currents were suitable for the different activities to take place safely, so using TBM’s in such case would have been a waste of time and money.
The box jacking tunneled section is optimum since using a TBM would have induced vibrations that could have harmed the railway above it.

26. Case Study #2: The Channel Tunnel, France-Uk
Objective: To connect the two countries and connect Britain to the rest of Europe
Cost: £4.65 billion
Duration: 6 years
Longest under water section in the world: 37.9 Km
Five TBM’s used, each designed for the geology of a specific length of the project.
EPBM to withstand the high water pressure while Boring
The longest TBM : 200 m long

27. The Channel Tunnel, France-Uk
The TBM’s were lowered into the drilled shafts at both ends
Prefabricated concrete tunnel sections are placed continuously using hydraulic arms to make a support around which acts as a permanent lining.

28. The Chunnel: Flow Chart
Geological Survey
Establish TBM course
Drilling Shafts at both ends
Installing proper ventilation system
Lowering TBMs in the Shafts
TBM excavates
TBM conveys earth soil outside for disposal
Temporary rails transport Concrete sections to TBM head
TBM places pre-cast concrete slabs for tunnel lining
Process continues until both TBMs reach meeting point
TBM disposal

29. Case Study 2: Method Evaluation
The channel between the UK and France is well known for unstable weather conditions and extreme currents. Hence, using the immersed tunneling technique would have been difficult and of very high risks.
The box jacking method was unsuitable for usage in case of such a long tunnel.
Using TBM’s in such case was the only possible option.
The type of TBM’s could have been altered to use only two multi- mode TBM’s to take into account the possible variation in ground conditions instead of having five different TBM’s and disposing some of them.

30. Conclusion The most governing factor of choice is the soil conditions
The safety, level of risk, constructability, speed and cost.
Selection criteria matrix to take all the factors governing the method selection into account as neglecting some of them could cause serious problems that are difficult in fixing.

31. References

32. Thank You