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GEOCONSULT
NATM Applications in Singapore
Ground Conditions
Dr. Oskar SIGLDr. Oskar SIGL
Geoconsult Asia Singapore
1NATM Workshop 2010
TUCSS Course Singapore; 09 June 2010
Mined TunnelsMined TunnelsSHAFT-BSHAFT-BESCAPE SHAFTESCAPE SHAFT
LINKWAYLINKWAY
CIRCLE LINE (OUTER)CIRCLE LINE (OUTER)
SHAFT-ASHAFT-A
DOWNTOWN LINE (OUTER)
CIRCLE LINE (INNER)
DOWNTOWN LINE (OUTER)
CIRCLE LINE (INNER)
DOWNTOWN LINE (INNER)DOWNTOWN LINE (INNER)
2NATM Workshop 2010
Design Issues
» Understand sequence of works and
Design Issues
» Understand sequence of works and stage the excavation & support application
» At all times maintain stability of the excavation face
» Design should extend into the gconstruction phase
3NATM Workshop 2010
Cyclic Activities in TunnellingCyclic Activities in Tunnelling
» Activities (excavation, loading, mucking, support i ll i ) f d i i h ifiinstallation) are performed in sequence with specific equipment
» Typical work cycles correspond to defined excavation steps and support systems
» Collapses happen during temporary stages
Drilling
Loading and Blasting
Ventilation
Scaling
Mucking
5NATM Workshop 2010
Support Installation
Sequencing – C705 DTSS Advance TunnelSequencing – C705 DTSS Advance Tunnel
Top HeadingTop Heading
Bench
InvertInvertBack Fill
• Staged Excavation• Lattice girder, full round
7NATM Workshop 2010
• Shotcrete & wire mesh
Detailing – C705 DTSS Advance Tunnel
Top Heading
Detailing – C705 DTSS Advance Tunnel
p g
Bench
Invert B h8NATM Workshop 2010
Invert Bench
Sequencing - CCL1 C825 Overrun TunnelsSequencing DTSS/T03 TBM Launching chamberSequencing - CCL1 C825 Overrun TunnelsSequencing – DTSS/T03 TBM Launching chamber
Top Heading
Bench
Invert
9NATM Workshop 2010
Excavation Sequencing within the FaceExcavation Sequencing within the Face
FACESUPPORTING
BODYBODY
» Increase immediate Support by reduction of excavation area
12NATM Workshop 2010
Face Stability - ForepolingFace Stability - Forepoling
Shape of excavationwithout forepolingwithout forepoling
17NATM Workshop 2010
ForepolingForepoling
» Advance support ahead of excavation face
» Provides support for the free span = unsupported excavation surface = indirect face support
» Needs support element on its own (soil Needs support element on its own (soil and lattice girder)
» Effective only for initial support» Effective only for initial support
» Normally no permanent function at all
18NATM Workshop 2010
Face Stability - ForepolingFace Stability - Forepoling
Shape of excavationwithout forepolingwithout forepoling
Shape of excavationShape of excavationwith forepoling
20NATM Workshop 2010
ForepolingForepoling
» Forepoling needs support element on its own (otherwise cantilever action)
» One end in soil (adequate rebar length)
» Other end rests on lattice girder (connect rebar to girder)(connect rebar to girder)
» Adequate spacing is an important » Adequate spacing is an important parameter
21NATM Workshop 2010
Face Stability – DTL 1 C905Face Stability – DTL 1 C905
Advance support ahead of excavation faceProvide support for exposed round
22NATM Workshop 2010
Provide support for exposed roundNeeds support (soil and lattice girder)
DTL 1 C905DTL 1 C905Stacked CCL Tunnels= LOWER by NATMy= Upper by TBM
Stacked DTL Tunnelsbelow CCL C&C
Launch Shaft A
Launch Shaft BStacked DTLLaunching chambersLaunching chambers
C&
CC
CL1
25NATM Workshop 2010
25
DTL 1 C905 – Underpassing CCL C&CDTL 1 C905 – Underpassing CCL C&C
RL 103.00
1. D-wall InstallationReclamation-----------------------
RL 80 50 m
2. Excavation and Ring Beam (Concrete)
3. Roof Slab Construction
S C
Kallang Formation
RL 80.50
RL 70.77
46.2
5m 4. Intermediate Slab Construction
5. Base Slab Construction
---------------------------Old Alluvium
TL 56.75
RL 61.257. DTL Outer Tunnel Construction
8 Backfill and Reinstate8. Backfill and Reinstate
26NATM Workshop 2010
26
DTL 1 C905DTL 1 C905Stacked CCL Tunnels= LOWER by NATM= Upper by TBM= Upper by TBM
Launch Shaft A
C&
CC
CL1
27NATM Workshop 2010
27
DTL 1 C905 – NATM with ground treatment
GROUND
DTL 1 C905 – NATM with ground treatment
Promenade StationRL 103.00
LAUNCH SHAFT A
GROUND TREATMENT BY JET GROUTING
RL. 73.34
LOWER CCLNATM TUNNEL
UPPER CCLTBM TUNNEL
28NATM Workshop 2010
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Pipe Roof – Heavy ForepoliongPipe Roof – Heavy Forepoliong
» Support free span (unsupported length) at the faceat the face
Pi f l d h i th» Pipe roofs are longer and heavier than forepoling and of larger size
» Typically applied in difficult ground and/or for tunnelling with low overburden
30NATM Workshop 2010
Face Support – Face BoltingFace Support – Face Bolting
» addresses sliding and spalling» cut back after each advance» continuous thread
35NATM Workshop 2010
Construction Concepts – Pilot TunnelConstruction Concepts Pilot Tunnel
Orchard Road – C825 Overrun Tunnels
37NATM Workshop 2010
Geotechnical Longitudinal SectionGeotechnical Longitudinal SectionPedestr. Underpass
Potential Faults
38NATM Workshop 2010
Orchard Road – C825 Overrun TunnelsOrchard Road – C825 Overrun Tunnels
Pilot Tunnel Concepts
Istana
Pilot Tunnel Concepts
SB CL
NB CL
39NATM Workshop 2010
Construction Concepts – Pilot TunnelConstruction Concepts Pilot Tunnel#1 Individual Pilot Tunnel
Pilot tunnel required by PS
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Construction Concepts – Pilot TunnelConstruction Concepts Pilot Tunnel#2 Pilot Heading
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Pilot Tunnel – CCL C825Pilot Tunnel – CCL C825
B ki f Pil t T l d i T h di E ti
45NATM Workshop 2010
Breaking of Pilot Tunnel during Topheading Excavation
Pilot Tunnel – CCL C825Pilot Tunnel – CCL C825
Pilot Tunnel
Pil H di
46NATM Workshop 2010
Pilot Heading
Special Application – DTSS Shaft ESpecial Application – DTSS, Shaft E
» 5 Tunnels intersecting the Shaft structure» 5 Tunnels intersecting the Shaft structureDe-aeration Chamber& Back shunt T04
T06
T03
50NATM Workshop 2010
T03
Special Application – DTSS Shaft ESpecial Application – DTSS, Shaft E
» 5 Tunnels intersecting the Shaft structurestructure
Th t l i t f th» The tunnel openings remove most of the Shaft lining
» How to arrive at a reasonable approach for the structural design of temporary shaft lining
51NATM Workshop 2010
DTSS T06/R2 – Influence Lines
Settlement Influence Lines above Crown 17.6.02 to 18.7.02
DTSS T06/R2 – Influence Lines
S-6116 S-6120 S-6122 S-6126 S-6127 S-6129 S-6133 S-6134
- 17.06.02 -
- 24.06.02 -
S-6135 S-6139
0
10
- 600 mm Gas Main -- 01.07.02 -
- 08.07.02 --20
-10
[mm
]
- 15.07.02 -
-40
-30
Settl
emen
ts [
TRENDLINE
-60
-50 17.06.02 24.06.02
01.07.02 08.07.02
15.07.02 trend
-7014.0 19.0 24.0 29.0 34.0 39.0 44.0 49.0 54.0 59.0
Chainage [m]
57NATM Workshop 2010
DTSS T06/R2 – Influence Lines
Settlement Influence Lines above Crown 17.6.02 to 19.8.02
DTSS T06/R2 – Influence Lines
S-6116 S-6120 S-6122 S-6126 S-6127 S-6129 S-6133 S-6134
- 17.06.02 -
- 24.06.02 -
S-6135 S-6139
0
10
- 600 mm Gas Main -- 01.07.02 -
- 08.07.02 --20
-10
[mm
]
- 15.07.02 -
- 22.07.02 -
- 12.08.02 -
- 19.08.02 -
-40
-30
Settl
emen
ts
- 29.07.02 - - 05.08.02 -
-60
-50 17.06.02 24.06.0201.07.02 08.07.0215.07.02 22.07.0229.07.02 05.08.0212.08.02 19.08.02
TRENDLINE
-7014.0 19.0 24.0 29.0 34.0 39.0 44.0 49.0 54.0 59.0
Chainage [m]
trendTRENDLINE
58NATM Workshop 2010
DTSS T06/R2 – Influence LinesSettlement Influence Lines above Crown 19.8.02 to 23.9.02
S 6127 S 6129 S 6133 S 6134 S 6135 S 613910
DTSS T06/R2 – Influence Lines
S-6127 S-6129 S-6133 S-6134 S-6135 S-6139
-10
0
- 600 mm Gas Main -
- 19.08.02 -
-20
[mm
]
TRENDLIN
- 22.07.02 -
- 05 08 02 -
- 12.08.02 -
19.08.02
- 26.08.02 -
-40
-30
Settl
emen
ts [
- 29.07.02 - - 05.08.02 -
- 02.09.02 -
- 09.09.02 -
- 23.09.02 -
-60
-50
S
17.06.02 24.06.0201.07.02 08.07.0215 07 02 22 07 02
- 16.09.02 -
-80
-70
32 0 34 0 36 0 38 0 40 0 42 0 44 0 46 0 48 0 50 0 52 0 54 0 56 0 58 0 60 0 62 0
15.07.02 22.07.0229.07.02 05.08.0212.08.02 19.08.0226.08.02 02.09.0209.09.02 16.09.0223.09.02 trend
59NATM Workshop 2010
32.0 34.0 36.0 38.0 40.0 42.0 44.0 46.0 48.0 50.0 52.0 54.0 56.0 58.0 60.0 62.0
Chainage [m]
DTSS T06/R2 – Influence Lines
Construction Progress
DTSS T06/R2 – Influence Lines
g
S-6116 S-6120 S-6122 S-6126 S-6127 S-6129 S-6133 S-6134 S-6135 S-6139
26 08 02
02.09.02
09.09.02
- 600 mm Gas Main -
12.08.02
19.08.02
26.08.02
29.07.02
05.08.02
Dat
e
Stop of excavation work to seal tunnel
15.07.02
22.07.02
01.07.02
08.07.02
10.0 15.0 20.0 25.0 30.0 35.0 40.0 45.0 50.0 55.0 60.0Chainage [m]
60NATM Workshop 2010
Side GalleriesSide Galleries
»Reduce size of excavation face
»Face stability
»Control of Settlements
63NATM Workshop 2010
Side GalleriesSide Galleries
»Make sequence only as complicated as necessary
»Avoid additional (structural) complicationscomplications
64NATM Workshop 2010
Side Galleries – Common “Design Trap”Side Galleries – Common Design Trap
Analyses result in largeAnalyses result in large horizontal deformation
L l li d ti fLarge localised section forces (particular issue = shear design)design)
Requirement for horizontal strutting due to the above
Serious construction issueSerious construction issue
Better structure ??
66NATM Workshop 2010
Side Galleries – Common “Design Trap”Side Galleries – Common Design Trap
Better structure ??Better structure ??
67NATM Workshop 2010