Discontinuum Modeling of Underground Power House Excavation - A Case Study
Underground Excavation Behavior of the Queenston Formation
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Transcript of Underground Excavation Behavior of the Queenston Formation
Geomechanics ColloquyWorkshop on Failure Prediction in GeotechnicsSalzburg, Austria
Austrian Society for Geomechanics
Underground Excavation Behaviour of the Queenston Formation - Tunnel back analysis
Matthew Perras, Prof. Mark Diederichs (Queen’s University) and Helmut Wannenmacher (Marti Tunnelbau AG. formerly Strabag Inc.)
Geomechanics ColloquyWorkshop on Failure Prediction in GeotechnicsSalzburg, Austria
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Presentation Outline
• Introduction • Geomechanical Settings • Rock Mass Behaviour • Tunnel back analysis • Lessons learnt!
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Tunnel
The Falls Whirlpool
Intake The TBM
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1 km
St David’s
Escarpment
Niagara GorgeNiagara Falls
Rapids
Whirpool
Introduction NTFP _ The Niagara Region
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Construction of two tunnel back in the 1950 ties
Introduction NTFP _ Tunnel Alignment
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Introduction NTFP _ Geological Section
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The NTFP: Excavation and Support
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The NTFP: Problem Statement
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Problem Statement
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Geomechanical Settings What is the trigger for this adverse rock mass conditions?
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Southern Ontario
DGR
Niagara Tunnel
CanadaCanada
Geomechanical Settings_ Regional Setting
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DGRNiagara Tunnel
Geomechanical Settings _ The Queenston Formation
NTFP
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Bois Blanc
Salina
Niagara Group
Cataract Group
Queenston
Georgian Bay
Blue MountainCollingwoodCobourg
Bass Island
Lucas
Amherstburg
Geomechanical Settings _ Variances in Stiffness
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Geomechanical Settings _ Variances in UCS and CI
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Geomechanical Settings _ Influence of Siltstone Layers
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Tunnel
Geomechanical Settings _ Stress Field at the NTP
Tunnel
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Rock Mass Behaviour
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Rock Mass Behaviour _ Classification of Rock Mass Behaviour
Observed area
Zone 4 Zone 3 Zone 2 Zone 1
Geomechanics ColloquyWorkshop on Failure Prediction in GeotechnicsSalzburg, Austria
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Irondequoit
Age Formation Brief Description
Grey crystalline dolomitic Limestone Lockport
Decew
Grimsby
Power Glen
Whirlpool
Queenston Red shale and argillaceous limestone
Light grey crossbedded sandstone
Grey shale to white calcareous sandstone
Green, irregularly bedded sandstone with red shale
interbeds
Grey to reddish dolomitic limestone
Crystalline dolomite &grey mudstone
Ordov- ician
Low
er
Sil
uri
an
Cata
ract
A
lbem
arl
e
Cli
nto
n
Mid
dle
Sil
uri
an
Light grey crystalline dolomite
Neahga
Gro
up
Thorold
Reynales
White sandstone
Rochester
Green shale
Dark grey calcareous shale dolomite interbedded
Approx.
Thickness (m)
Symbol
335
3.6 – 7.6
11.5
16
1.2 – 3.1
17.7
2.1 – 4.0
2.4 1.8
3.6
Shallow Chimeny
Gravity Raveling
Localized Haunch Fractures
Haunch Failure
Rock Mass Behaviour _ Zone 1
Geomechanics ColloquyWorkshop on Failure Prediction in GeotechnicsSalzburg, Austria
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Irondequoit
Age Formation Brief Description
Grey crystalline dolomitic Limestone Lockport
Decew
Grimsby
Power Glen
Whirlpool
Queenston Red shale and argillaceous limestone
Light grey crossbedded sandstone
Grey shale to white calcareous sandstone
Green, irregularly bedded sandstone with red shale
interbeds
Grey to reddish dolomitic limestone
Crystalline dolomite &grey mudstone
Ordov- ician
Low
er
Sil
uri
an
Cata
ract
A
lbem
arl
e
Cli
nto
n
Mid
dle
Sil
uri
an
Light grey crystalline dolomite
Neahga
Gro
up
Thorold
Reynales
White sandstone
Rochester
Green shale
Dark grey calcareous shale dolomite interbedded
Approx.
Thickness (m)
Symbol
335
3.6 – 7.6
11.5
16
1.2 – 3.1
17.7
2.1 – 4.0
2.4 1.8
3.6
Rock Mass Behaviour _ Zone 2
Joints
Irregular Profile
Large Blocks
Stress concentration from
stiff to weak layer
Shear failure along the planes of
weakness
Contact Area of Sandstone and Mudstone
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Rock Mass Behaviour _ Zone 3
Irondequoit
Age Formation Brief Description
Grey crystalline dolomitic Limestone Lockport
Decew
Grimsby
Power Glen
Whirlpool
Queenston Red shale and argillaceous limestone
Light grey crossbedded sandstone
Grey shale to white calcareous sandstone
Green, irregularly bedded sandstone with red shale
interbeds
Grey to reddish dolomitic limestone
Crystalline dolomite &grey mudstone
Ordov- ician
Low
er
Sil
uri
an
Cata
ract
A
lbem
arl
e
Cli
nto
n
Mid
dle
Sil
uri
an
Light grey crystalline dolomite
Neahga
Gro
up
Thorold
Reynales
White sandstone
Rochester
Green shale
Dark grey calcareous shale dolomite interbedded
Approx.
Thickness (m)
Symbol
335
3.6 – 7.6
11.5
16
1.2 – 3.1
17.7
2.1 – 4.0
2.4 1.8
3.6
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Rock Mass Behaviour _ Depth of Overbreak
1.5km3.5 km 2.5 km3.0km 2.0 km
0
1
2
3
4
Max
ove
rbre
ak d
epth
(m
)
Geomechanics ColloquyWorkshop on Failure Prediction in GeotechnicsSalzburg, Austria
Austrian Society for Geomechanics
Irondequoit
Age Formation Brief Description
Grey crystalline dolomitic Limestone Lockport
Decew
Grimsby
Power Glen
Whirlpool
Queenston Red shale and argillaceous limestone
Light grey crossbedded sandstone
Grey shale to white calcareous sandstone
Green, irregularly bedded sandstone with red shale
interbeds
Grey to reddish dolomitic limestone
Crystalline dolomite &grey mudstone
Ordov- ician
Low
er
Sil
uri
an
Cata
ract
A
lbem
arl
e
Cli
nto
n
Mid
dle
Sil
uri
an
Light grey crystalline dolomite
Neahga
Gro
up
Thorold
Reynales
White sandstone
Rochester
Green shale
Dark grey calcareous shale dolomite interbedded
Approx.
Thickness (m)
Symbol
335
3.6 – 7.6
11.5
16
1.2 – 3.1
17.7
2.1 – 4.0
2.4 1.8
3.6
Rock Mass Behaviour _ Zone 4
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Rock Mass Behaviour _ Comparison of Zones
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Tunnel back analysis
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• Damage Initiation and Spalling Limit “DISL” (Diederichs 2007)– Without dilation– With dilation
• Ubiquitous Joint - Spalling – As above, with addition of ubiquitous joints
• Laminated Anisotropic MethodJoint elements used to induce anisotropy
Isotropic No Laminations
Anisotropic Laminations
Tunnel back analysis
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Niagara Tunnel Project NTP – Laminated Model
Tunnel back analysis _Failure Envelops
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Isotropic – No Laminations Anisotropic – With Laminations
Far Field
Sigma 1 = 12 MPa
33 44
Crown Stress Concentration
(MPa)
Tunnel back analysis _Elastic Stress Comparison
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Anisotropic – With Laminations
Far Field
Sigma 1 = 12 MPa
44
Crown Stress Concentration
(MPa)
Transversely Isotropic – No Laminations
44
Numerical Approach_Elastic Stress Comparison
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Deformed Boundary
Deformed Boundary
Far Field
Sigma 1 = 12 MPa
Isotropic – No Laminations Anisotropic – With Laminations
Tunnel back analysis _Plastic Displacement Comparison
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3.95 m3.78 m
Tunnel back analysis _Ubiquitous Joint
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Tunnel back analysis _ NTP Back Analysis
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Lessons learnt !
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• Queenstone shale as a brittle material demands for more sophisticated analyses to capture realistic rock mass behaviour.
• Mineralogical differences are the source of the planes of weakness and trigger the failure process.
• DISL / Ubiquitous Joint method can capture overbreak dimensions, but were unable to capture chord closure measurements.
• LAM method can capture both overbreak dimensions and chord closure measurements.– The anisotropic stiffness plays an important role in the failure mechanism
when beam deflect can occur
Lessons learnt!
Geomechanics ColloquyWorkshop on Failure Prediction in GeotechnicsSalzburg, Austria
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Thanks for your audience.