1. Construction Beam Tunnel
October 12th 2011
ILC-CFS Face-to-face meeting

2. Contents
Background of reviewing NATM applicability for beam tunnel excavation in JAPAN
Current status of Tunnel construction in Japan
Introduction NATM / TBM
Comparison TBM vs. NATM
Supplemental construction work
Safety of tunnels and shafts

3. Background of reviewing NATM for beam tunnel excavation in JAPAN
One of the most important recent study was ,,,
“Availability NATM for ILC Beam tunnel”
RDR
TBM construction and circular section was selected for Beam tunnel.
TDR, next stage study
More detailed study should be required.
Is TBM construction best choice for Japanese candidate site?
Case study was carried including NATM case

4. Current status of Tunnel construction in Japan
According to tunnel construction database Japan Tunnel Association
Others
Utility conduit
Water way
Road
Railway
Number of construction

5. Current status of Tunnel construction in Japan Mountainous site tunnel achievement
Many tunnels are constructed by NATM
TBM case is not so many as NATM
Others
TBM
B & M
Blasting
Machine
Upper and lower
Long bench
NATM
Machine
Number
NATM
Blasting
Full face with short bench
Full face
Blasting
Machine
Full face
Short Bench
Long Bench

6. Current status of Tunnel construction in Japan Example of typical TBM application
Water way tunnel, headrace or tailrace tunnel of hydropower plant.
Friction loss reduced in case of a circular section
Minimize specific surface area
Highway evacuation tunnels.
Evacuation tunnel is constructed as an investigation tunnel.
Section shape is almost fixed D=4.5 m standardized.
Railway tunnels in urban area, soft or weak ground
Shield type TBM is applied for soft or weak soil ground excavation.
XFEL tunnels are excavated by TBM in the same reason.
Pilot tunnel in case of large section tunnel excavation
In “2nd TOMEI High Way” construction case, 5m diameter TBM tunnel was applied as a pilot tunnel.
Many reinforcing supports (cable bolts or fiber bolts) were placed as a fore-support.

7. Introduction NATM New Austrian Tunneling Method
NATM is a designing concept of rock support or a construction method.
Concept Secure excavated rock surface stability by using flexible rock support. (reasonable support design)
Method Shotcrete, rock bolt, steel support, (blasting / machine )
Dr. Rabcewicz (Austrian) published the concept of NATM in engineering Journal “Water Power” in 11/1964, based on European tunnel construction experience.
The concept spread over the world and of course it is familiar tunneling method in Japan.

8. How to excavate tunnels by NATM Procedure of tunnel excavation1 3
1. Drilling of blasting hole
2. Filling blasting powder
3. Blasting
4. Mucking 2 4
5. Removing floating rock
6. Face observation
7. Shotcreting
8. Rockbolt installation 2 5
9. Reinforcement
10. Lining concrete placing

9. How to excavate tunnels by NATM Procedure of tunnel excavation6
1. Drilling of blasting hole
2. Filling blasting powder
3. Blasting
4. Mucking 7 9
5. Removing floating rock
6. Face observation
7. Shotcreting
8. Rockbolt installation 8 10
9. Reinforcement
10. Lining concrete placing

10. Introduction of TBM Types of TBM
Excavating by cutting forward rock with rotating and pressing the full face cutter head.
Securing the cutter head pressing force is important.
Shield type TBM
Open type TBM
Machine body is wrapped by cylindrical skin plate.
Segments are installed for permanent support within excavation cycle.
Machine body is opened.
No permanent support, shotcrete as a temporally support. Conc. lining is necessary in other procedure.
Pressing force is from segments
Pressing force is from surrounding rock mass through main gripper.
Water tight lining by segments
Little more permeable lining
Construction cost is higher
Economical than Shield type

11. Introduction of TBM Types of TBM
Shield type TBM
Open type TBM

12. Comparison TBM vs. NATM Excavation Speed
TBM excavation is faster than NATM.
Averaged actual TBM ex. speed is 220 m/Month in Japan.
In RDR, 300 m/M, assumed for the good geology condition
US 700m/M, Euro 400m/M
NATM speed is roughly 100 m/M.
But the TBM speed advantage would be reduced
5km interval access tunnel, TBM:5km ex. NATM : 2.5km ex.
Both of contraction periods are almost the same.
Additionally, beam tunnel TBM ex. must be held by completion of access hall (shaft-base cavern) ex. because of TBM assembling.
In NATM case, access hall and the tunnel can be simultaneously started.
Effect of excavation speed is almost equal

13. Comparison TBM vs. NATM Loosened zone expansion of bedrock
By NATM excavation, loosened zone extent to surrounding rock, because of variation of ground-stress, and blasting impact.
But in TBM case, loosening occurs only by variation of ground-stress.
In JTA investigation, NATM case is 2 times deeper than TBM case.
But the rock property of loosened zone is not critical level.
E Modulous (Gpa)
Depth of loosened zone (m)
Fresh
Loosened
Piling
NATM
TBM
D5m
D10m A 15 6
0.8
1.3
0.4
0.7
0.2
0.3 B 12
4.8
1.5
2.3
1.2
0.6 CH
2.4
1.9
2.9
1.0
0.5 CM
2.5 1
3.5
1.8
0.9 CL
2.3<
3.5<
1.2<
1.8<
0.6<
0.9< D
0.12
Fresh
Diameter
Loosened
Loosened zone is not seemed critical issue

14. Comparison TBM vs. NATM Difference of rock support
TBM can excavate more smoothly and less damaged, rock bolts are not used.
Rock bolts sometimes cause seepage inflow.
Grouting work will increase in NATM excavation.
High permeable
layer
If rock bolt hole penetrates high permeability zone, much groundwater might discharge to inside of the tunnel.

15. Comparison TBM vs. NATM Noise, vibration, low-frequency noise
Noise and vibration caused by blasting will be the one of the most important environmental problem.
Blasting noise: from underground to surface ground via tunnel portal.
Blasting vibration: from underground to surface ground directly
These affects will be larger in a residential region.
Shallow tunnel, vibration impact
Access tunnel, noise impact, near the portal area
Countermeasures for noise and vibration
Restriction of blasting time
Blasting only day time
Machinery excavation
Free face drilling machine. But not applicable for hard rock
Control blasting
Partial blasting, upper / lower. Wedge cutting blasting
Multi step blasting using electronic detonator

16. NATM by excavating machine
Free face excavating machine / partial face excavating machine
They have a drilling boom with drum or disc mounted hard bits.
By moving the boom according to designed shape, various section can be excavated.
Lower noise and vibration than by blasting.
Slower excavation speed than by blasting, in case of hard rock.
Usually applicable less than 100～200MPa (rock strength)　
Road Header
Mobile Miner
Mobile Tunneling Machine

17. Control blasting 2 step blasting 4 step blasting 8 step blasting
level
level
level
time
time
time
By increasing the blasting step, reducing the maximum vibration level.

18. Comparison TBM vs. NATM Over-brake and under-brake
TBM tunneling, almost excavate as designed shape.
NATM tunneling : over brake and under brake.
In Japanese public construction case, 30 cm over brake for hard granitic rock case, is accepted
Included excavating cost
TBM construction cost and schedule
Machine price, transportation cost, assembling and dismantling cost are higher.
Long period is required for design and fabrication.
TBM is not good for short tunnel

19. Comparison TBM vs. NATM Cost, Schedule, Tunneling flexibility,
Flexibility for tunneling
Generally cross section shape can not be changed in TBM excavating.
Not easy to excavate Local cavern in TBM case.
In NATM case, section change and Local cavern ex. can be easily.
Flexibility for supplementary work
Many kind of supplementary work can be applied easily In NATM case.
TBM case will be subject to various constraints, because of work space.

20. Supplemental construction work Underground seepage inflow control
１．Grouting work : Reduction of seepage inflow rate
Injecting cement slurry to high permeable zone.
Improve the permeability, and reduce seepage rate.
Pre-grouting
Grouting for the area to be excavated
Drilling forward from tunnel face
Post-grouting
Grouting for excavated area
Drilling from tunnel wall
２．Drainage work
Drilling drainage borehole to high permeable area
Drain off groundwater from the area prier to excavation
Drained groundwater should be pumped out to outside of tunnel during construction or more if not reduce.

21. Supplemental construction work Underground seepage inflow control
Forward explore drilling
Injection
Proceed excavation
Progress excavation
Drilling injection hole

22. Supplemental construction work Outline of grouting work
Drilling injecting hole
Measuring seepage rate and pressure
Permeability test
Injecting cement slurry
Completion of injection
Drilling test hole
Measuring seepage rate and pressure
Permeability test
insufficient
confirming permeability
sufficient
completion
Drilling test hole

23. Safety of access tunnel and access shaft
We have two choice for access to underground caverns and tunnels, by sloped tunnel (about 10% inclination) or by vertical shaft.
Vertical shaft is shorter than sloped tunnel.
In case of emergency, electrical power failure, how do we escape from underground space?
Shaft.
Short length
Not easy to climb
Sloped tunnel
Long length
By vehicles
Both access way can satisfy the sufficient safety level.
It is only necessary to equip required safety facilities in access shaft or tunnel

24. Example Road tunnel safety facilities standardAA A B C D
notification system
Alarm system x
fire extinguishing equipment
evacuation guidance
other equipment
traffic quantity (number/day)
Distance of tunnel (m)