large tbm projects in switzerland – experience and state of the art
TRANSCRIPT
FJELLSPRENGNINGSDAGEN, BERGMEKANIKKDAGEN, GEOTEKNIKKDAGEN 2012
LARGE TBM PROJECTS IN SWITZERLAND – EXPERIENCE AND STATE OF THE ART
Part 2
Johannes Gollegger & Helmut Wannenmacher
Amberg Engineering Ltd., Switzerland
Content
2
Fjellsprengningsdagen, Bergmekanikkdagen, Geoteknikkdagen Oslo, November 22 -23, 2012
1. Introduction
3. Risk-based geotechnical design
4. Case study Lago Bianco Hydropower
6. Remaining risks of TBM tunnelling
2. Lessons learned from recent projects
5. Uncertainties in the prediction of penetration rates
Introduction
3
Fjellsprengningsdagen, Bergmekanikkdagen, Geoteknikkdagen Oslo, November 22 -23, 2012
Switzerland 40 years of experience
Development of TBM
Improved well established technique
Lessons learned
Remaining risks
Content
4
Fjellsprengningsdagen, Bergmekanikkdagen, Geoteknikkdagen Oslo, November 22 -23, 2012
1. Introduction
3. Risk-based geotechnical design
4. Case study Lago Bianco Hydropower
6. Remaining risks of TBM tunnelling
2. Lessons learned from recent projects
5. Uncertainties in the prediction of penetration rates
2.1 Vereina Tunnel
2.2 Gotthard Base Tunnel
Vereina Railway Line
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Fjellsprengningsdagen, Bergmekanikkdagen, Geoteknikkdagen Oslo, November 22 -23, 2012
Geology of the Vereina Tunnel
Crystalline rock mass, gneisses and amphibolites Foliation is flatly bedded, fissures show narrow spacing
Experience Gained at the Vereina Tunnel
6
Fjellsprengningsdagen, Bergmekanikkdagen, Geoteknikkdagen Oslo, November 22 -23, 2012
Crown failure some sections excavated by TBM
1st causal factor Existing geology, flatly bedded foliation
2nd causal factor Thrust force, bracing of TBM against the tunnel wall →Gripper force can lead to opening of existing fissures→Opening of fissures in existing geology led to crown failure
Experience Gained at the Vereina Tunnel
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Fjellsprengningsdagen, Bergmekanikkdagen, Geoteknikkdagen Oslo, November 22 -23, 2012
→Increased supporting measures→Drop down of advance rate
Excavation rates
Content
8
Fjellsprengningsdagen, Bergmekanikkdagen, Geoteknikkdagen Oslo, November 22 -23, 2012
1. Introduction
3. Risk-based geotechnical design
4. Case study Lago Bianco Hydropower
6. Remaining risks of TBM tunnelling
2. Lessons learned from recent projects
5. Uncertainties in the prediction of penetration rates
2.1 Vereina Tunnel
2.2 Gotthard Base Tunnel
Experience Gained at the Faido Single-Track Tubes
9
Fjellsprengningsdagen, Bergmekanikkdagen, Geoteknikkdagen Oslo, November 22 -23, 2012
Damages at Following Excavation of West Tube
Invert heaves behind cutter head including heave of invert concrete
Contact between back-up constructions and rock support
Experience Gained at the Faido Single-Track Tubes
10
Fjellsprengningsdagen, Bergmekanikkdagen, Geoteknikkdagen Oslo, November 22 -23, 2012
Stress redistribution process
Development of arch
subhorizontal rock foliation
Primary stressEST-East
EST-West
Stress redistribution due to excavation of West tube
Deformations of invert and
crown
Stress redistribution due to excavation East tube
11
Fjellsprengningsdagen, Bergmekanikkdagen, Geoteknikkdagen Oslo, November 22 -23, 2012
Radial deformation [cm]
0 5 10 15 20 25 30
0.5
0
1
1.5
2
3
2.5
Pre
ssu
re [
MP
a]
Ground reaction curve after excavation of the first tube
Ground reaction curve after excavation of the second tube
Flexible lining
Stiff lining
Failure of rock support
Residual resistance
Failure of rock support
Required rock support
Required rock support
Experience Gained at the Faido Single-Track TubesGround reaction curve
Experience Gained at the Faido Single-Track Tubes
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Fjellsprengningsdagen, Bergmekanikkdagen, Geoteknikkdagen Oslo, November 22 -23, 2012
Encountered geological conditions
Experience Gained at the Faido Single-Track Tubes
13
Fjellsprengningsdagen, Bergmekanikkdagen, Geoteknikkdagen Oslo, November 22 -23, 2012
Crown collapse West tube, blocking of TBM, first countermeasures
6 m long weak zone of kakiritic and cataclastic material > TBM was blocked Installation of 4 pipe umbrellas Filling of space above cutter head with concrete Countermeasures failed
Experience Gained at the Faido Single-Track Tubes
14
Fjellsprengningsdagen, Bergmekanikkdagen, Geoteknikkdagen Oslo, November 22 -23, 2012
Crown collapse West tube, blocking of TBM, additional countermeasures Gel grouting above TBM in order to protect cutter head
from cement grouting Cement grouting in order to stabilize collapsed zone Adit from east tube
> TBM freed after
20 weeks
Experience Gained at the Faido Single-Track Tubes
15
Fjellsprengningsdagen, Bergmekanikkdagen, Geoteknikkdagen Oslo, November 22 -23, 2012
Lessons learned
Largest possible overcut Robust shield and cutter head Shield with variable diameter Shortest possible shield Sufficiently large thrust force The capability of installing flexible support The capability of installing support simultaneously with tunnel
driving
Content
16
Fjellsprengningsdagen, Bergmekanikkdagen, Geoteknikkdagen Oslo, November 22 -23, 2012
1. Introduction
3. Risk-based geotechnical design
4. Case study Lago Bianco Hydropower
6. Remaining risks of TBM tunnelling
2. Lessons learned from recent projects
5. Uncertainties in the prediction of penetration rates
Risk Based Geotechnical Design
17
Fjellsprengningsdagen, Bergmekanikkdagen, Geoteknikkdagen Oslo, November 22 -23, 2012
TBM excavationresonable
Conventional excavation
Evaluation of excavation method
Definition of rock mass behaviour
Relevant geotechnical parameters
Primary stress conditions
Size, shape, location of structure
Orientation of ground structure
Ground water
Definition of ground types
no
yes
Risk Based Geotechnical Design
18
Fjellsprengningsdagen, Bergmekanikkdagen, Geoteknikkdagen Oslo, November 22 -23, 2012
Risks acceptable
Evaluation of remaining risks
Choice of TBM concept including rock support
Behaviour at shield
Behaviour fulfils the requirements
Behaviour at back-up
Behaviour at cutter head
Definition of system behaviour
no
yes
noyes
Content
19
Fjellsprengningsdagen, Bergmekanikkdagen, Geoteknikkdagen Oslo, November 22 -23, 2012
1. Introduction
3. Risk-based geotechnical design
4. Case study Lago Bianco Hydropower
6. Remaining risks of TBM tunnelling
2. Lessons learned from recent projects
5. Uncertainties in the prediction of penetration rates
20
Fjellsprengningsdagen, Bergmekanikkdagen, Geoteknikkdagen Oslo, November 22 -23, 2012
Lago Bianco HydropowerGeological, longitudinal profile
2000
3000
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Lago Bianco
1000
Lago di Poschiavo
2000
3000
Stretta and Berninacrystalline with Alv zone
Berninathrust zone
Musellagranite
Margnanappe
Malenconappe
Margnanappe
Marinelliformation
Sellanappe
Sellanappe
Musellagranite
© Bild Repower
Source: www.repower.com
Experience gained at the Lago Bianco Hydropower
21
Fjellsprengningsdagen, Bergmekanikkdagen, Geoteknikkdagen Oslo, November 22 -23, 2012
Homogeneous zone A, chainage 1+090 to 6+820
Massive to blocky gneisses and shists Overburden up to 850 m Stable rock mass behaviour Potential of gravitational overbreaks Inhomogeneous face conditions → higher wear rates
Experience gained at the Lago Bianco Hydropower
22
Fjellsprengningsdagen, Bergmekanikkdagen, Geoteknikkdagen Oslo, November 22 -23, 2012
Homogeneous zone A, chainage 1+090 to 6+820
Massive to blocky gneisses and shists Overburden up to 850 m Stable rock mass behaviour Potential of gravitational overbreaks Inhomogeneous face conditions → higher wear rates
Experience gained at the Lago Bianco Hydropower
23
Fjellsprengningsdagen, Bergmekanikkdagen, Geoteknikkdagen Oslo, November 22 -23, 2012
Homogeneous zone B, chainage 6+820 to 7+020
Overburden approx. 950 m , large deformations, shear failure in crown Risk of jamming of TBM Shield lubrication, shifting of gauge cutters, grouting Local water ingress und limited flowing ground conditions Measures: Segmental lining, pipe umbrella, drainage borehole Risk acceptable
Experience gained at the Lago Bianco Hydropower
24
Fjellsprengningsdagen, Bergmekanikkdagen, Geoteknikkdagen Oslo, November 22 -23, 2012
Homogeneous zone B, chainage 6+820 to 7+020
Overburden approx. 950 m , large deformations, shear failure in crown Risk of jamming of TBM Shield lubrication, shifting of gauge cutters, grouting Local water ingress und limited flowing ground conditions Measures: Segmental lining, pipe umbrella, drainage borehole Risk acceptable
Experience gained at the Lago Bianco Hydropower
25
Fjellsprengningsdagen, Bergmekanikkdagen, Geoteknikkdagen Oslo, November 22 -23, 2012
Homogeneous zone C, chainage 14+760 to 16+050
Non-cohesive fault zone, stress induced shear- failure Major water inflow (up to 210l/s) > risk of flowing ground conditions High load on TBM shield and on segments > high risk of jamming Risk not acceptable
Experience gained at the Lago Bianco Hydropower
26
Fjellsprengningsdagen, Bergmekanikkdagen, Geoteknikkdagen Oslo, November 22 -23, 2012
Homogeneous zone C, chainage 14+760 to 16+050
Non-cohesive fault zone, stress induced shear failure Major water inflow (up to 210l/s) > risk of flowing ground conditions High load on TBM shield and on segments > high risk of jamming Risk not acceptable
Experience gained at the Lago Bianco Hydropower
27
Fjellsprengningsdagen, Bergmekanikkdagen, Geoteknikkdagen Oslo, November 22 -23, 2012
Tunnelling concept
Double shield TBM Trapezoidal segments Pea gravel and grouting of annular gap Flat cutter head Anti-wear plates and wedges Equipment for exploration drilling Umbrella pipe Lubrication of shield Pumping devices of up to 250 l/s, Possibility of probe drillings Segments with higher reinforcement and load capacity, with
drainage tubes
Content
28
Fjellsprengningsdagen, Bergmekanikkdagen, Geoteknikkdagen Oslo, November 22 -23, 2012
1. Introduction
3. Risk-based geotechnical design
4. Case study Lago Bianco Hydropower
6. Remaining risks of TBM tunnelling
2. Lessons learned from recent projects
5. Uncertainties in the prediction of penetration rates
Uncertainties in the Prediction of Penetration Rates
29
Fjellsprengningsdagen, Bergmekanikkdagen, Geoteknikkdagen Oslo, November 22 -23, 2012
Geological and geotechnical influencing factors for penetration prediction models
Uncertainties in the Prediction of Penetration Rates
30
Fjellsprengningsdagen, Bergmekanikkdagen, Geoteknikkdagen Oslo, November 22 -23, 2012
Influences on penetration rate
Clogging of mucking buckets (left) Cutter failure due to dynamic loads (right)
Uncertainties in the Prediction of Penetration Rates
31
Fjellsprengningsdagen, Bergmekanikkdagen, Geoteknikkdagen Oslo, November 22 -23, 2012
Influences on penetration rate
Unaxial compressive strength Normally oriented angle of fabric towards tunnel axis > maximum penetration Parallel oriented angle > minimum penetration Stress conditions at the tunnel face Failure mode
Content
32
Fjellsprengningsdagen, Bergmekanikkdagen, Geoteknikkdagen Oslo, November 22 -23, 2012
1. Introduction
3. Risk-based geotechnical design
4. Case study Lago Bianco Hydropower
6. Remaining risks of TBM tunnelling
2. Lessons learned from recent projects
5. Uncertainties in the prediction of penetration rates
Risk Based Geotechnical Design
33
Fjellsprengningsdagen, Bergmekanikkdagen, Geoteknikkdagen Oslo, November 22 -23, 2012
Remaining uncertainties of TBM tunnelling are related
To false prediction of system behaviour
>> Ground investigation with a risk based geotechnical
design
>> Action plan with countermeasures To false prediction of penetration rate
>> Reliable failure modes for the determination of
the advance rate
A design for the “Worst Case” is certainly technically desirable, but cannot always be implemented with economically justifiable means!!!
Thank You Very Much For Your Attention!
Thank You Very Much For Your Attention!