NATM Applications in Singapore Ground Conditions

GEOCONSULT

NATM Applications in Singapore Ground Conditions Dr. Oskar SIGL Geoconsult Asia Singapore

TUCSS Course Singapore; 09 June 2010

NATM Workshop 2010

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Mined Tunnels SHAFT-B

ESCAPE SHAFT LINKWAY

CIRCLE LINE (OUTER)

DOWNTOWN LINE (OUTER) CIRCLE LINE (INNER)

SHAFT-A DOWNTOWN LINE (INNER)

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Design Issues

» Understand sequence of works and stage the excavation & support application

» At all times maintain stability of the excavation face

» Design g should extend into the construction phase NATM Workshop 2010

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Excavation Cycle

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Cyclic Activities in Tunnelling » Activities (excavation, loading, mucking, support iinstallation) ll i ) are performed f d in i sequence with i h specific ifi equipment

» Typical work cycles correspond to defined excavation steps and support systems

» Collapses happen during temporary stages Drilling Loading and Blasting Ventilation Scaling Mucking Support Installation NATM Workshop 2010

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Typical Sequencing

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Sequencing – C705 DTSS Advance Tunnel

Top Heading

Bench

Invert Back Fill

• Staged Excavation • Lattice girder, full round • Shotcrete & wire mesh NATM Workshop 2010

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Detailing – C705 DTSS Advance Tunnel Top p Heading g

Bench

Invert NATM Workshop 2010

B Bench h 8

CCL1 C825 Overrunchamber Tunnels Sequencing –- DTSS/T03 TBM Launching Top Heading

Bench

Invert

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Sequencing – DTL1 C905

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Sequencing

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Excavation Sequencing within the Face

FACE SUPPORTING BODY

» Increase immediate Support by reduction of excavation area NATM Workshop 2010

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Excavation Sequencing within the Face

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Excavation Sequencing – C704 CP3

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Special Equipment – Tunnel Excavator

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Special Equipment – Tunnel Excavator

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Face Stability - Forepoling

Shape of excavation without forepoling

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Forepoling » 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 and lattice girder)

» Effective only for initial support » Normally no permanent function at all NATM Workshop 2010

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Shape of excavation without forepoling

Shape of excavation with forepoling

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Forepoling » 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)

» Adequate spacing is an important parameter

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Face Stability – DTL 1 C905

Advance support ahead of excavation face Provide support for exposed round Needs support (soil and lattice girder) NATM Workshop 2010

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Forepoling Hand drill (auger) with air leg – CCL C825

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DTL 1 C905 Stacked CCL Tunnels = LOWER by y NATM = Upper by TBM

Launch Shaft A

Stacked DTL Tunnels below CCL C&C Stacked DTL Launching chambers

CCL1 C&C

Launch Shaft B


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DTL 1 C905 – Underpassing CCL C&C RL 103.00

1. D-wall Installation Reclamation -----------------------

2. Excavation and Ring Beam (Concrete) Kallang Formation

46.25m m

3. Roof Slab Construction RL 80.50 80 50 RL 70.77

4. Intermediate S Slab C Construction --------------------------Old Alluvium

5. Base Slab Construction

RL 61.25 TL 56.75

7. DTL Outer Tunnel Construction 8 Backfill and Reinstate 8.


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DTL 1 C905 Stacked CCL Tunnels = LOWER by NATM = Upper by TBM

CCL1 C&C

Launch Shaft A


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DTL 1 C905 – NATM with ground treatment

RL 103.00

LAUNCH SHAFT A

GROUND TREATMENT BY JET GROUTING

Promenade Station

RL. 73.34

LOWER CCL NATM TUNNEL

UPPER CCL TBM TUNNEL 28

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Pipe Roof – Heavy Forepoliong

» Support free span (unsupported length) at the face

» Pipe Pi roofs f are longer l and d heavier h i than th forepoling and of larger size

» Typically applied in difficult ground and/or for tunnelling with low overburden NATM Workshop 2010

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Pipe Roof

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Pipe Roof – NEL C704 TBM Launching

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Pipe Roof – CCL 3 C852 Advance Tunnel

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Pipe Roof – CCL 4 C855

Equipment Drilling Jumbo

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Face Support – Face Bolting

» addresses sliding and spalling » cut back after each advance » continuous thread NATM Workshop 2010

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Sequencing with Face Bolting

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Construction Concepts – Pilot Tunnel

Orchard Road – C825 Overrun Tunnels

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Geotechnical Longitudinal Section Pedestr. Underpass

Potential Faults

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Orchard Road – C825 Overrun Tunnels Pilot Tunnel Concepts

Istana Æ

SB CL

NB CL NATM Workshop 2010

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Construction Concepts – Pilot Tunnel #1 Individual Pilot Tunnel

Pilot tunnel required by PS

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Construction Concepts – Pilot Tunnel #2 Pilot Heading

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Pilot Heading Max forces

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Horizontal Core Drilling Results

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Pilot Tunnel – CCL C825 Individual Pilot Tunnel

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Pilot Tunnel – CCL C825

B Breaking ki off Pil Pilott Tunnel T l during d i Topheading T h di Excavation E ti NATM Workshop 2010

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Pilot Tunnel – CCL C825

Pilot Tunnel

Pil H Pilot Heading di NATM Workshop 2010

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Enlargement to Final Size & Shape

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Ventilation Cross Tunnel

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Ventilation Cross Tunnel

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Special Application – DTSS, DTSS Shaft E

» 5 Tunnels intersecting the Shaft structure De-aeration Chamber & Back shunt

T04

T06

T03 NATM Workshop 2010

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Special Application – DTSS, DTSS Shaft E

» 5 Tunnels intersecting the Shaft structure

» The Th tunnel t l openings i remove mostt off the th Shaft lining

» How to arrive at a reasonable approach for the structural design of temporary shaft lining NATM Workshop 2010

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Design of Shaft Lining with Tunnel Eyes

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Design of Shaft Lining with Tunnel Eyes

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Application – DTSS Shaft E

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DTSS T06 – Shaft/Tunnel R2

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DTSS T06 – Shaft/Tunnel R2 600mm GAS MAIN

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DTSS T06/R2 – Influence Lines Settlement Influence Lines above Crown 17.6.02 to 18.7.02 10

S-6116 0

S-6120

S-6122

S-6126

S-6127

S-6129

S-6133

S-6134

S-6135

S-6139

- 17.06.02 - 24.06.02 -

-10

Settlements [[mm]

- 01.07.02 -

- 600 mm Gas Main - 08.07.02 -

-20

-30

- 15.07.02 -

TRENDLINE -40

-50

17.06.02

24.06.02

01.07.02

08.07.02

15.07.02

trend

-60

-70 14.0

19.0

24.0

29.0

34.0

39.0

44.0

49.0

54.0

59.0

Chainage [m]

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S-6116 0

S-6120

S-6122

S-6126

S-6127

S-6129

S-6133

S-6134

S-6135

S-6139

- 17.06.02 - 24.06.02 -

-10

Settlements [mm]

- 01.07.02 -

- 600 mm Gas Main - 08.07.02 -

-20

- 19.08.02 -

-30

- 15.07.02 - 22.07.02 -

-40

- 12.08.02 -

- 05.08.02 -

- 29.07.02 -

-50

-60

-70 14.0

17.06.02 01.07.02 15.07.02 29.07.02 12.08.02 trend

TRENDLINE

19.0

24.0

29.0

34.0

39.0

44.0

49.0

54.0

24.06.02 08.07.02 22.07.02 05.08.02 19.08.02

59.0

Chainage [m]

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S 6127 S-6127

S 6129 S-6129

S 6133 S-6133

S 6134 S-6134

S 6135 S-6135

S 6139 S-6139

0

-10

- 600 mm Gas Main -

Settlements [[mm] S

-20

TRENDLIN

- 19.08.02 -

-30 - 22.07.02 -

-40

- 12.08.02 - 26.08.02 -

- 05.08.02 05 08 02 -

- 29.07.02 -

-50 - 23.09.02 - 02.09.02 -

-60

17.06.02 01.07.02 15 07 02 15.07.02 29.07.02 12.08.02 26.08.02 09.09.02 23.09.02

- 09.09.02 -

- 16.09.02 -

-70

-80 32 0 32.0

34 0 34.0

36 0 36.0

38 0 38.0

40 0 40.0

42 0 42.0

44 0 44.0

46 0 46.0

48 0 48.0

50 0 50.0

52 0 52.0

54 0 54.0

56 0 56.0

58 0 58.0

24.06.02 08.07.02 22 07 02 22.07.02 05.08.02 19.08.02 02.09.02 16.09.02 trend

60 0 60.0

62 0 62.0

Chainage [m]

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DTSS T06/R2 – Influence Lines Construction Progress g 09.09.02 S-6116

S-6120

S-6122

S-6126

S-6127

S-6129

S-6133

S-6134

S-6135

50.0

55.0

S-6139

02.09.02 26 08 02 26.08.02 - 600 mm Gas Main -

19.08.02

Date

12.08.02 05.08.02 29.07.02 22.07.02 Stop of excavation work to seal tunnel

15.07.02 08.07.02 01.07.02 10.0

15.0

20.0

25.0

30.0

35.0

40.0

45.0

60.0

Chainage [m]

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Side Galleries

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Side Galleries

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Side Galleries

» Reduce size of excavation face » Face stability » Control of Settlements

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Side Galleries

»Make sequence only as complicated as necessary

»Avoid additional (structural) complications

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Side Galleries – Common “Design Design Trap” Trap

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Side Galleries – Common “Design Design Trap” Trap Analyses result in large horizontal deformation Large localised L l li d section ti forces f (particular issue = shear design) Requirement for horizontal strutting due to the above Serious construction issue Better structure ?? NATM Workshop 2010

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Side Galleries – Common “Design Design Trap” Trap Better structure ??

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Side Galleries

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Side Galleries

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Side Galleries

Thank You A d Glück And Glü k Auf A f NATM Workshop 2010

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