EOSC433: Geotechnical Engineering Practice & Design

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EOSC433EOSC433::

Geotechnical Geotechnical Engineering Engineering

Practice & DesignPractice & Design

Lab 1: Case Histories Lab 1: Case Histories --Campo Campo VallemaggiaVallemaggia & & GotthardGotthard Base TunnelBase Tunnel

1 of 35 Dr. Erik Eberhardt EOSC 433 (Term 2, 2005/06)

Campo Campo VallemaggiaVallemaggia


Campo Vallemaggia, CH

Geology - metamorphic gneisses & schistsMechanism – translational slide (30° SSE)Surface Area - ~ 6 km2

Total Volume - ~ 800,000,000 m3

Average Velocity - ~ 5 cm/yearMaximum Depth - ~ 300 m

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Campo Campo VallemaggiaVallemaggia –– Integrating Data SetsIntegrating Data Sets


Bonzanigo et al. (2006)




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Campo Campo VallemaggiaVallemaggia –– Slide KinematicsSlide Kinematics



Campo Campo VallemaggiaVallemaggia –– Deep Drainage MitigationDeep Drainage Mitigation


Bonz

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1300

1350

1400

1989 1990 1991 1992 1993 1994 1995 1996 1997 1998Bor

ehol

e H

ead

(m)

788

788.2

788.4

788.6

788.8

1989 1990 1991 1992 1993 1994 1995 1996 1997 1998Geo

detic

Mov

emen

t (m

)

0

1

2

3

4

Vel

ocity

(mm

/day

)

critical threshold at 1390 m

Bonz

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Campo Campo VallemaggiaVallemaggia –– Mitigation OptionsMitigation Options


Eber

hard

t et

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(200

6)

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Campo Campo VallemaggiaVallemaggia –– Mitigation ResultsMitigation Results


1300

1350

1400

1989 1990 1991 1992 1993 1994 1995 1996 1997 1998Bor

ehol

e H

ead

(m)

788

788.2

788.4

788.6

788.8

1989 1990 1991 1992 1993 1994 1995 1996 1997 1998Geo

detic

Mov

emen

t (m

)

0

1

2

3

4

Vel

ocity

(mm

/day

)

drainage adit opened

critical threshold at 1390 m

Bonz

anig

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Campo Campo VallemaggiaVallemaggia –– Mitigation ResultsMitigation Results


-600

-500

-400

-300

-200

-150

-100

-50

Vertical component1993-94

mm/year

-600

-500

-400

-300

-200

-150

-100

-50

Total settlement with drainage

1995-1998

mm

… geodetically measured surface displacements showing down-slope displacements before deep drainage, and the development of a settlement trough (i.e. consolidation) after deep drainage.

BEFORE Drainage AFTER Drainage


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Campo Campo VallemaggiaVallemaggia –– Mitigation OptionsMitigation Options


Campo Campo VallemaggiaVallemaggia –– Coupled HCoupled H--M M AnaysisAnaysis


0.00

0.50

1.00

1.50

20000 60000 100000

Time Steps

Pore

Pre

ssur

e (M

Pa)

adit level

20 m above adit

40 m above adit

60 m above adit

0.00

0.50

1.00

1.50

20000 60000 100000

Time Steps

Pore

Pre

ssur

e (M

Pa)

adit level

20 m above adit

40 m above adit

60 m above adit

drainageadit

opened

Eberhardt et al. (2006)

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Campo Campo VallemaggiaVallemaggia –– Coupled HCoupled H--M M AnaysisAnaysis


0.01

0.10

1.00

10.00

20000 60000 100000

Time Steps

X -

Dis

plac

emen

ts (m

)

without pore pressures (i.e. dry slope)

without drainage adit

with drainage

aditdrainage adit

openedCampo Vallemaggia:Distinct-element models suggest that very little drainage is required (approximately 10 l/s) to significantly reduce pore pressures and to stabilize the slope.

Deep Drainage:Fracture permeability corresponds to low storativities, therefore large water inflows through drainage are not necessary to achieve significant reductions in head.

Tunnelling in SwitzerlandTunnelling in Switzerland


200734.6Loetschberg (CH)

199450.5Chunnel (ENG-FR)

198853.9Sei-kan (Japan)

2012*57.1Gotthard Base (CH)

Completion Date

Length(km)

Tunnel

WorldWorld’’s Longest Transportation Tunnelss Longest Transportation Tunnels

#30 Mount MacDonald (CAN) @ 14.6 km#43 New Cascade (USA) @ 12.5 km

Canada = 5 rail tunnels > 2 km USA = 4 rail tunnels > 2 km

Switzerland = 42 rail tunnels > 2 km

Gotthard Road Tunnel (CH) = 16.9 km

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Tunnelling in SwitzerlandTunnelling in Switzerland


Canada = 5 rail tunnels > 2 kmUSA = 4 rail tunnels > 2 km

Switzerland = 42 rail tunnels > 2 km

200734.6Loetschberg (CH)

199450.5Chunnel (ENG-FR)

198853.9Sei-kan (Japan)

201257.1Gotthard Base (CH)

Completion Date

Length(km)

Tunnel

WorldWorld’’s Longest Transportation Tunnelss Longest Transportation Tunnels

#30 Mount MacDonald (CAN) @ 14.6 km

Gotthard Road Tunnel (CH) = 16.9 km

Estimated Costs:

$7 Billion CDN

$4 Billion CDN

Financing:

10% Oil Tax 15% Loans55% Heavy Vehicle Tax20% 1% increase in VAT

AlpTransitAlpTransit Base TunnelsBase Tunnels


In 1994 the Swiss voted an alpine protection article into the Swiss constitution. This forbade the expansion of capacity on transit roads in alpine regions and obliged the government to shift heavy goods traffic from road to rail. Accordingly, voters approved the “Alptransit” project to build new tunnels through the Gotthard and the Lötschberg, and to charge heavy vehicles fees that ensure they pay for the cost they cause to society.

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Reasons for Base TunnelsReasons for Base Tunnels


Increasing Population Demands & Commercial Traffic- The Gotthard Road Tunnel, is the

main north-south route through the Alps, between Italy and Switzerland.

- 18,000 vehicles/day pass through the Gotthard Road Tunnel.

SafetySafety

Gotthard Road Tunnel Fire (2001) – 11 people killed

PollutionPollution

Drivers going through the Gotthard Road Tunnel inhale as many pollutants as if they smoked up to eight cigarettes.

AlpTransitAlpTransit Base TunnelsBase Tunnels


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AlpTransitAlpTransit Design SpecificationsDesign Specifications


2000 2005 2010 2015 2020 2025

2000 Lötschberg 2007

2000 Gotthard 2012

2006 Zimmerberg 2013

2006 Ceneri 2016

2011 2016

2007 2011

Neat

AusbautenSt. Gallen – Arth-Goldau

VerbindungZürichsee – Gotthard

LLöötschbergtschberg Base TunnelBase Tunnel


Drill & Blast

TBM

Length = 34.6 km Total tunnel system = 88.1 km Distance between parallel tubes = 40 m Gradient: 3‰ (north), 11‰ (south) Elevation, Frutigen north portal 776.5 m Elevation, Raron south portal 654.2 mExcavated material = 16 million tonnes

80%80%

20%20%

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LLöötschbergtschberg Base Tunnel Base Tunnel –– Geological PrognosisGeological Prognosis


Loew

et

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(200

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LLöötschbergtschberg Base Tunnel Base Tunnel –– Geological ChallengesGeological Challenges


The path of the Lötschberg passed under the Gästern Valley, 200 m below the valley floor. It was estimated that the alluvial sediments extended 100 m below surface leaving 100 m of strong limestone to form the roof of the tunnel.

Buried Valleys: burial is the consequence of glacial down cutting and alluvial deposition. Buried valleys are a major concern in tunnelling as they are often deep (!!), with unknown thicknesses, and filled with water saturated sediments under high water pressures.

In actuality, the buried valley reached depths of more than 185 m. By July 24, 1908, the tunnel had advanced such that only a thin wall of rock divided the working-face from the buried valley. Within seconds of that morning’s blast, 40,000m3 of water saturated sediments swept into the tunnel killing 25 men and filling the tunnel for a distance 1.25 km.

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LLöötschbergtschberg Base Tunnel Base Tunnel –– Geological ChallengesGeological Challenges


Karst:

Given the porous nature of karst, large volumes of water and a high risk of water ingress was expected over a section about 3 km long. It was constantly necessary to carry out preliminary boring in order to discover whether any large, water-filled karstsink-holes might endanger the tunnel driving operations.

1.5m

GotthardGotthard Base TunnelBase Tunnel


Length = 57 km

Sedrun shaft = 800 m

Distance between parallel tubes = 40 m

Excavated material = 24 million tonnes

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GotthardGotthard Base Tunnel Base Tunnel –– Geological PrognosisGeological Prognosis


Loew

et

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GotthardGotthard Base Tunnel Base Tunnel –– Geological ChallengesGeological Challenges


Geologic Unit Potential

Key Hazard Tectonic

Unit Max. Length

Cataclastic Faults High pressure water inflow.

Crystalline Massifs, Penninic Gneisses

∼100 @ 5m

Weak Rocks (Phillites, Schists, Cataclasites)

Strongly squeezing ground.

Crystalline Massifs 1.3 km

Granites Rockburst. Crystalline Massifs >14 km

Sugar Grained Dolomites

Water saturated debris inflow, cohesionless rock.

(Par)autochthonous Triassic Sediments

∼200 m

Loew

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The first Gotthard rail tunnel was constructed between 1872-1882, and cut the travel time from Zurich to Milan from 27 to 5.5 hours. However, 310 men died and 877 were incapacitated during construction of the 14.9 km tunnel. Numerable challenges and harsh conditions were encountered, many of which were augmented by the equally harsh contract signed by the tunnel designer Louis Favre .

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Lützenkirchen (2003)

Zang

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Laws et al. (2003)

Granitic Fault Rocks Aar Massif(σ3=5MPa)



Loew et al. (2000)

Fault zones may form highly permeable conduits for groundwater, leading to tunnel inflows. Encountering large quantities of water may lead to flooding of the excavation, especially if there is no outlet for the water to drain to.

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The tunnel will cross the Triassic Piora Zone, a highly weathered and fractured aquifer under high hydraulic pressure. Based on exploratory drilling, the tunnel will luckily pass ~250 meters below the base of the aquifer through unweathered and unfractured dolomite/ anhydrite-sequences.

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GotthardGotthard Base Tunnel Base Tunnel –– Other ChallengesOther Challenges


More than 13 million m3 of waste rock will be generated, leading to environmental issues as to where to put it. At the same time, the extraction of gravel resources for concrete in the Swiss midlands is becoming more difficult. The solution, therefore, is to specially break, sort & wash the waste rock so that it can be used for concrete aggregate.

Given that tunnel overburden will exceed 2000m, temperatures as high as 45°C are projected. In addition, silicosis, an incurable disease of the lungs, caused by the unprotected respiration of quartz dust presents a potential hazard to workers. Ventilation designs must account for both factors to ensure worker safety.

GotthardGotthard Base Tunnel Base Tunnel –– Unexpected ChallengesUnexpected Challenges


Subsidence above old mine workings in the U.K.

Land subsidence due to extraction of large volumes of fluids from 1925 and 1977 in San Joaquin Valley, California.

Ground Collapse Consolidation

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“Poison ratio” effect

∆σn´= ∆σn - αf∆pnormal deformation(i.e. closure)

Zang

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key dams

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GotthardGotthard Base Tunnel Base Tunnel –– Unexpected ProblemsUnexpected Problems


Zang

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EOSC433: Geotechnical Engineering Practice & Design

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