Engineering Issues Related to Mined...

1 1

Society of Myanmar Civil Engineers (Singapore)

Engineering Issues Related to Mined

Tunnels

Dr. Oskar SIGL – Geoconsult Asia Singapore

Singapore; 16 October 2016

2 2

Mined Tunnels – SCL/NATM/SEM

Content

Latest Developments on mined tunneling supporting

method

Controlling soft ground

3 3

Mined Tunnels – SCL/NATM/SEM

Terminology

SCL – Sprayed Concrete Lining

NATM – New Austrian Tunneling Method

SEM – Sequential Excavation Method

Observational Approach

Shotcrete Sprayed Concrete

4 4

Example: Mined Station; Seattle

SoundTransit

Beacon Hill Station

5 5

Example: Mined Station; London

LUL Jubilee Line Extension

Contract 102 Waterloo Station

6 6

Example: DTSS Advance Tunnel; Singapore

North East Line

Contract C705

7 7

Example: Overrun Tunnels; Singapore Orchard Road

Circle Line 1 – Overrun Tunnels

Contract C825 Dhoby Ghaut Station

8 8

Example: NS3 Cable Tunnel; Singapore

Tunnels for TBM operation and cable

enlargements

9 9

Example: EW1 Cable Tunnel; Singapore

Mined tunnel

10 10

Key Issues

Are not rocket science

Understand the general sequence of tunneling and

the staging of excavation & support application

Pay attention to deformation control and ground

confinement

Recognize the importance of design adjustments

during construction

Maintain stability of the excavation face at all times

Understand why people call it “high risk”

Mined Tunnels

11 11

Characteristics of Work Processes

Linear development of the work zone with limited

space and accessibility

Repetition of working steps (work cycles)

Transient intermediate stages (sections with

incomplete liner)

Mined Tunnels

12 12

Mined Tunnel - Construction

Sequencing of Excavation & Support

Constitutes major part of the design

13 13

Sequencing/staging DETAILING

Staged Excavation

Lattice girder, full round in soft ground

Shotcrete & wire mesh


14 14

Top Heading

Bench

Invert Bench

Typical sequencing/staging


15 15


16 16


17 17


18 18

Steel Rib / Arch

Not embedded in shotcrete

Function Load distribution

Support of “green” shotcrete

Profile control

Support for forepoling

Traditional Types H-beams

Channels with sliding connection

Lattice girder

19

Channel with sliding connection

20 20

Layout Options:

“Standard”

“Optional”

Lattice girder – For embedment in shotcrete

21 21

Face Stability

Advance support of excavation face

Forepoling / pipe umbrella / spiling

22 22

Advance support ahead of excavation face

Provide support for exposed round

Needs support (soil and lattice girder)

Ground Support

Forepoling DETAILING

23 23

Special Equipment – Tunnel Excavator

24 24

Special Equipment – Tunnel Excavator

25 25

Pipe Umbrella / Pipe Roof

Same concept as forepoling

but stronger & heavier & longer

Advance Support Ahead of Excavation Face

26 26

Pipe Umbrella / Pipe Roof


27 27

Pipe Roof

28 28

Casagrande Rig

Pipe Roof

29 29

Jumbo

Pipe Roof

30

Pipe Roof

31 31

Forepoling – Soft ground

Support soil in front of the “next” face

Reduce soil loading for the soil wedge defining face

stability

Spacing typically 150-300mm c/c

T25 rebars, mostly grouted

Length > advance length (typically 1.5 x)

Tied into lattice girder of previous round


32 32

Face Stability

Effects of Advance Support

Wedge 1 & Wedge 2

33 33

Face Stability – Design of Advance Support

Wedge 1 situation

Support of free

advance length

34 34

Face Stability – Design of Advance Support

Wedge 2 situation

Supporting load

on top of wedge

35 35

Spiling – Rock

Same concept as forepoling but in rock

Rock bolting inclined forwards in order to avoid

overbreak in the next blasting round

Spacing typically >500mm c/c

Length ≈ advance length

“Does not need a lattice girder”


36 36

Spiling to reduce overbreaks

37 37

EXAMPLE: Face stability in Praxis

39 39

Loose Gravel

Dense Gravel

Silt Stone

Dense Gravel

Tunnel

EXAMPLE: Face stability in Praxis

40 40

Face stability in Praxis

Subdivide excavation face

Increase immediate support by reduction of

excavation area

Start where it is worst, use the better area for

support

FACE

SUPPORTING

BODY

41 41

Example – Face Stability Recover, small faces

42 42

Recover, small faces

43 43

Recover, small faces

44 44

Drainage

Forepoling

Face bolts

Face

Dumpling

45 45

103.03m

101.48

Existing 1.2m Water Pipe

PIPE

800mmx11mm thk

Ground Level 109.43 (approx.)

Supporting Steel Frame

~ 94.00m

Change of shallow cover pipe pile box

tunnel to a mined tunnel with shotcrete

Application to Complicated Problems

SUBWAY STRUCTURE

46 46

Pipe Roof Cross Section – Pipe Pile Box

47 47

Existing 1.2m Water Pipe

Application to Complicated Problems

SUBWAY STRUCTURE

One tunnel too shallow

48 48

SCL Cross Section - Sequencing

49 49


50 50


Half of permanent

structure

Temp. props

51 51


52 52


53 53


54 54

Longitudinal Section & Ground Condition

Pipe Roof Sections

Water Pipe

FILL & Peaty clay

Silty Clay

Cemented silty sand

55 55

Sequential Excavation with Pipe Roof

Install Pipe roof Sections overlap more pipe layers

Top heading

Temporary invert

56 56

Construction

Pipe Roof

57 57

Ground Treatment

Details of face grouting arrangement

Design of drilling / grouting pattern

58 58

2D Analysis

Mined Tunnel 2 (Staged Top Heading &

Bench/Invert excavation)

Face & pipe roof grouting

Temporary Prop

“Fill concrete”

Permanent Structure

Connection DETAIL

Tunnel 2

Horizontal face grouting + Pipe Roof

installation and grouting

Staged excavation of Top Heading &

Bench/Invert (short ring closure)

Casting of second half permanent

structure

59 59

3D Analysis

60 60

Pipe Roof Drilling

61 61

Excavation

62 62

SECTION 2 double pipe roof

SECTION 1 double pipe roof

Construction

63 63

Excavation – Top Heading

64 64

Pipe roof pipe

Construction

65 65

Excavation – Top Heading

Face grouting pipes

66 66

Face Support – Top Heading

67 67

Face Grouting – Top Heading

68 68

Drilling of Face Grouting – 1st Drift

69 69

“Weak” support resistance of Lattice girder and temporary invert

Construction Issue

70 70

Excavation – 2nd Drift

71 71

2nd Drift Completed

72 72

Application to much Larger Schemes

73 73

Singapore Jurong Caverns

74 74

Storage Schematics and Terminology

Inlet shaft Pump Shaft

Water Curtain Tunnel & dill holes

Access tunnel

Water Curtain Tunnel & drill holes

Access tunnel Storage cavern

20 x 30 x 650m

75 75

Storage Schematics and Terminology

76 76

Water Curtain System

Permanent pressure gradient towards the cavern

Oil floats on top of a water cushion

Thickness of water cushion is regulated by water

pumps in pump shaft

77 77

Oil pump

Water pump

Water cushion

Crude Oil

Hot oil pipe

Storage of Crude Oil

78 78

Storage Principle

Hot oil pipe

79 79

Engineering

Engineering during construction

Geological Mapping

Geotechnical Documentation

Rock Support Classification

Rock support application

Geological prediction during construction

80 80

Implementation During Construction

Geological

Mapping sheet

81 81

Distribution of rock quality – Padur/A

82 82

Data Management

Geological documentation

83 83

Construction Sequencing

Gallery – Pilot and Slashings

Pilot Gallery Side Slashing - LEFT Side Slashing - RIGHT

84 84


Bench 1

Side Slashing

Pilot Bench

Bench 2

85 85


3 Benches

Gallery

Bench 1

Bench 2

Bench 3

86 86

Gallery

Bench 1

Bench 2

Bench 3

Excavation Stages

87 87

Pilot

Side slashing

Excavation Stages

88 88

Pilot Side slashing

Bench 1

Excavation Stages

89 89

Bench 2 Pilot Side slashing

Excavation Stages

90 90

Bench 3

Excavation Stages

91 91

21m

30m

12m

Excavation Stages

Pump sump

92 92

Cavern

Construction

93 93 Access tunnel portal

Construction

94 94

Access tunnel junction

95 95

Pump Shaft

Inlet Shaft

97 97

Inlet shaft

Vishakapatnam – Construction

98 98

Inlet shaft

99 99

Pump shaft

100 100

Pump shaft

101 101

Major Wedge Failure

102 102

Major Wedge Failure

103 103

Major Wedge Failure

Shear

Tension

Shear

Tension

Both

Sigma 1

MPa

0.00

1.80

3.60

5.40

7.20

9.00

10.80

12.60

14.40

16.20

18.00

0-1

0-2

0-3

0-4

0-5

0-6

0

-70 -60 -50 -40 -30 -20 -10 0 10 20 30 40 50 60 70 80

104 104

Major Wedge Failure

105 105

Major Wedge Failure

106 106

Thank You

Engineering Issues Related to Mined...

Documents

Transcript of Engineering Issues Related to Mined...