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Engineering Geodesy II: Tunnel Surveying I
Adrian Ryf
Head of Surveying and Data Coordination
AlpTransit Gotthard AG
22.04.2010
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About Adrian Ryf
� 1986 Diploma as „Kulturingenieur” at ETHZ
� 1986 – 1989 assistant and researcher at ETHZ – IGP (Prof. Chaperon / Carosio)
� 1989 – 1997 project engineer in a private surveying company in Locarno
� 1997 – 2007 assistant and lecturer at ETHZ – IGP (Prof. Ingensand)
� 2007 – head of surveying and data coordination at AlpTransit Gotthard AG
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Contents
� Introduction
� Basic principles
� Historical tunnel surveying
� Tunnel surveying nowadays
� AlpTransit project
� Intermediate attack of Sedrun
� Surveying requirements
� Basic network of the Gotthard base tunnel: position
� Basic network of the Gotthard base tunnel: height
� Surveying aspects in the shaft of Sedrun
� Impact of the tunnel construction at the surface
� Ceneri: monitoring A2
� End
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Island of Samos, Greece
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Eupalinos Tunnel
� oldest known tunnel, built from two sides of the hill
� 530 B.C.
� water supply
� length: 1 km
� breakthrough error:
� direction: 2 m
� height: 3 m
� distance ?
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Drawing of Heron
rectangular traverse, Pythagoras (580 – 500 B.C.)
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Basic principles of tunnel surveying
� Transfer of 3D-position from A to B
� Transfer of orientation from A to B
� Transfer of scale from A to B
aim: minimal breakthrough error
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Basic principles of tunnel surveying
A B
position, orientation and scale okay
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Basic principles of tunnel surveying
A B
start position in A wrong
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Basic principles of tunnel surveying
A B
orientation in A wrong
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Basic principles of tunnel surveying
A B
scale in A wrong
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Definitions
� breakthrough: location, inside a tunnel, where the independent tunnelling works from two sides meet. If a tunnel is built only from one side, the breakthrough coincides with one of the portals.
� a priori breakthrough prediction: a priori calculated accuracy for the breakthrough, relative confidence ellipsis of two close points, each on one side of the break-through without opposite geodetic measurements.
� effective breakthrough error: difference between actual and nominal value of the differences in length, lateral and in height between two close points, each on one side oft the breakthrough
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Tolerance – accuracy – reliability
� communication aspects:
� civil and geomatics specialists have different ideas about the signification of these terms
� civil engineers talk about accuracy when they mean (construction) tolerance
� e.g. the built tunnel axis may differ 15 cm of the axis of the project
� accuracy in geodesy: 1 σ (standard deviation)
� the construction tolerance matches more with the geodetic expression of the reliability
� reliability : accuracy ≈ factor: 2.5 – 3
a precise and written definition of the values is part of a goodquality management
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Historical surveying of tunnels: the Quanat method (light holes, orient)
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Prolongation of straight lines across the mountain
France – Italy: Mont Cenis
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Existing tunnels in the Swiss Alps
� Gotthard, Simplon
� traditional triangulation networks across the mountains
� straight line tunnels
� straight auxiliary tunnels at the portals: Airolo, Brig
� Lötschberg
� project of a straight line tunnel
� adjustment of the project due to geological reasons
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Networks of Gotthard and Simplon tunnel
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Lötschberg
Gasterntal
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Tunnel surveying nowadays
� tunnel network without tensions
� network of reference points, specially designed for a construction site
� consistent homogenous design
� free network adjustment
� three-part tunnel surveying system
� basic network
� portal network
� tunneling network
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Three-part tunnel surveying
GPS-network →→→→ tunneling networks→→→→ portal networks
ca. 2 – 3 km
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Basic tunnel surveying: position / height
� position
� high accuracy of GPS
� transfer of position, orientation and scale between portals
� height
� high accuracy of levelling, mostly national levelling network
� gravity aspects play an important role for long tunnels, systematic levellingerrors
� tectonic movements (e.g. convolution of the Alps)
� GPS height accuracy over big distances normally not good enough (troposphere influences)
� GPS: heights over the ellipsoid, good information about the geoid is essential
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A flat rail-link across the Alps
project idea 1947
shaft: 800 m
underground station19th century railway
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AlpTransit Lötschberg and Gotthard
www.alptransit.ch
Gotthardbase tunnel57 km long
Lötschbergbase tunnel37 km long
Ceneribase tunnel15 km long
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AlpTransit
� north - south (railway 2000: west - east)
� reduction of travelling time
� displacement of goods transports from the street to the railway
� reduction of energy consumption: less locomotives
� amelioration of quality of life in the valleys on both sides of the Gotthard (less trucks)
� Lötschberg: Spiez - Steg / Mund
� Lötschberg – opening of the base tunnel in december 2007
� www.blsalptransit.ch
� AlpTransit Gotthard: Zimmerberg, Arth-Goldau - Lugano
� Zimmerberg base tunnel (later), Gotthard and Ceneri base tunnel in construction
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Gotthard base tunnel
� 5 construction sites:
� north portal Erstfeld
� intermediate attacks of Amsteg, Sedrun and Faido
� south portal Bodio
� Line is curved:
� geological reasons
� construction sites in the valleys
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A flat railway-link across the Alps
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Travelling from Zurich to Milano
Intercity today
tilting train today
Gotthard base tunnel finished
all tunnels finished
complete new railway line
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Gotthard base tunnel: tunnel system
two tubes with lateral connections every 325 m
© AlpTransit
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Von 151,8 km Tunnel, Schächte, Stollen
sind 145 km oder 95,4% ausgebrochen
Ausbruch und Ausbau abgeschlossen
Ausbruch abgeschlossen
Bereit für Einbau Bahntechnik
Noch auszubrechende Tunnelröhren
Gotthard base tunnel – 01.04.2010
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Erstfeld
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Tunnel Amsteg – Sedrun
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Bodio
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New railway line near Biasca, ready for the installation of the track
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Geology
� especially Granit and Gneis → ideal for tunnel construction
� geological fault-zone between Aare- and Gotthard-Massif near Sedrun
� smaller geological fault-zones in different other places
Sedrun
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Intermediate attack Sedrun
diameter of shaft I: 8 m
1 km access tunnelfresh air tunnel
shaft cavern
2 shafts: 800 m
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Portal pillar in Sedrun
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In the access tunnel of Sedrun
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In the shaft cavern of Sedrun
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The first transportation system in the shaft
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At the bottom of the shaft (August 1999, ca. 360 m)
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At the bottom of the shaft (January 2005), shaft transportation plant
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Surveying requirements
tolerance (reliability) standard deviation
position (direction) 25 cm 10 cm
height 12.5 cm 5 cm
with the dimensions of a fist through the Alps
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A priori network design
11 cm
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Surveyors tasks outside of the tunnels and before tunnelling starts
� staking-out of construction sites, before the works start (Gotthard: 1995 in Sedrun)
� deformation measurements: tectonic movements
� deformation measurements: construction sites, portal areas
� coordination with the construction project (reservation of space and time for the surveying works)
� quality management
� minimization of risks
� etc.
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Minimization of risks
� always two different and independent methods
� different instruments
� independent controls
� augmentation of reliability
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Gotthard: basic network
Existing :
� National reference network LV03
� accuracy of neighboring points 2 - 4 cm
� absolute accuracy: several dm up to 1 m
� scale differences between north and south of Alps
� not good enough for long tunnels
� National levelling network LN02
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Existing networks: position
� network „Gerber“ 1973 – former AlpTransit project
� accuracy 2 - 4 cm
� not extended enough for the actual project
� new national network LV95, GPS
� highest accuracy: 1 cm absolute versus Zimmerwald
� few points, too far away from the portal areas
� big, inhomogeneous differences to LV03
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Steps for planning a basic network
� having a look at existing networks
� field control of existing points
� points in rock areas?
� points in instable areas?
� appropriate points for orientation sights
� discussions with geologists
� conversation with land owners
� definition of point type: pillar?
� analysis of construction plans: obstacles (huts, construction installations)
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GPS network
� preparation of GPS measurements
� mission planning (time schedule)
� instruments, measuring parameters, programming
� accessories: tripods, batteries, adapters, radios, mobile phones
� organization and instruction of the staff
� check of the instruments: optical plumbs, centering devices, antenna eccentricities, function control
� measurements
� 30 points in 2 days with 14 GPS instruments (Leica 200 / 300)
� 2 times 2 hours per point, alignment of all antennas to the north direction, careful centering
� network “Gerber” in 1972: about 2 months
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GPS network
every portal, every intermediate attack:
� minimum: 1 pillar
� 3 orientation points in a distance of 3-6 km (orientation transfer into the tunnel, reference for gyroscope and scale)
� 3 points of the national reference network LV03
6 points of the new national reference network LV95
GPS-Netz
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GPS post processing
� post processing with SKI (Leica GPS-software, Leica Geo Office)
� standard parameters
� no special troposphere models (height)
� no special ionosphere models (scale)
� use of precise ephemeris (internet download)
� transformation to the Swiss reference frame with Granit-parameters
� calculation of geoid separations with LAG to get orthometric heights (actually implemented in Leica Geo Office)
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Network adjustment with LTOP
� free network adjustment
� identical orientation for all GPS-coordinate-sets
� identical scale for all GPS-coordinate-sets
� a posteriori precision: 7 mm (longer axis of the biggest confidence ellipse)
� reliability: 26 mm
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Portal networks
� Immediately after the GPS measurements:
� measured with T3000 / T2000 and Mekometer ME 5000
� controlling scale and orientation of network
� further local reference points to control the pillars
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Portal networks
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LV03 or LV95 as reference for AlpTransit Gotthard??
� LV95 would be a good reference frame for AlpTransit
but:
� LV95 still not officially introduced in the project area
� differences between LV03 and LV95
� the AlpTransit project was designed in LV03
� cadastral system is LV03: land management, expropriations, etc.
� railway system is close to LV03
� changing the reference system during construction time is a high risk
� danger of errors and confusion
decision: AlpTransit Gotthard is built in LV03
� → Helmert-transformation on LV03-points in the areas of the north and the south portal
� differences in Sedrun and Faido have to be accepted
� scale factor always has to be corrected!
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Residuals in Sedrun and in Faido
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2005 control of the GPS network
GPS-measurements oft the network in summer 2005
� geodetic project course of ETH Zurich
� 28 points with the 28 GPS instruments
� 12 hours during the night, measured by students of ETH
comparison 1995 – 2005
� Helmert-transformation: maximal residuals: 1.5 cm
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2005 north portal Erstfeld
north portal
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2005 south portal Bodio
south portal
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Aspects of the height system
two national height systems:
� LN02, the actual height system
� LHN95, the height system of the future
decision: LN02 for AlpTransit Gotthard with the characteristics and the advantages of LHN95
LN02 LHN95
strict orthometric corrections no yes
tectonic movements (convolution of Alps) no yes
strict network adjustment no yes
new geoid no yes
project and realisation yes no
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Corrections in the tunnel
ca. 1 dm
1. strict orthometric correction
2. velocity correction
3. differences to LV03
convolution of Alps: Erstfeld +0.7 mm/year
Bodio +1.3 mm/year
gravity model, gravity measurements:= > correction amounts up to 12 cm
→difference: 0.6 year
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Orthometric corrections between Sedrun and Faido
shaft Sedrun intermediate attack Faido
55 mm
no difference between head and bottom of shaft
difference of models: < 1 cm© AlpTransit
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Surveying aspects in the shafts of Sedrun
� aimed accuracy:
� coordinates Y,X: 7 mm
� height: 3 mm
� direction: 1.5 mgon
� economical, time-saving methods are requested
� transfer of height
� vertical electronic distance measurement → gravity aspects
� transfer of position → deviations of vertical
� optical (with Nadir- or Zenith- plumb instrument) → refraction
� mechanical (with wires)
� transfer of direction
� gyroscope → deviations of vertical, temperature
� inertial measurements → drifts
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Position transfer
� methods
� optical
� mechanical
problems
refraction
visibility (fog)
vibrations
stable positioning of the instrument
expensive
oscillations
rain drops in the shaft
supply air of the ventilation
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Deviations of the vertical
� the plumb line in the shaft is curved
1400
1200
1000
800
600
400
west - east south - north
2.52.01.51.0 mgon
m.s.m.
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Deviations of the vertical
optical
mechanical
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Optical plumb measurement: campaigns
three optical plumb campaigns:
� in shaft I in March 2002
� in shaft II in January 2004
� in shaft I in January 2007
� ventilation: falling air frees the shaft from fog
� plumb measurement over 3 tripods: 3 different corridors
� nadir plumb instrument Leica NL
� at the feet of the shaft:
� special prisms with light diodes
� centering with precise translation stages (Kreuzschlitten)
� zenith plumb measurement impossible due to dropping rain
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Optical plumb measurement: top of the shaft
3 tripods
nadir plumb instrument
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Optical plumb measurement: bottom of the shaft
reflector on translation stagewooden stage over the “shaft cellar”
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Mechanical plumb measurement
� one plumb measurement campaign in March 2002
� specialized company from Gorleben (Germany): exploration of repositories for radioactive wastes
� 3 wires in 3 corridors in shaft I
� different weights: 390 kg – 195 kg – 390 kg
� determination of the wires with 2 theodolites
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Why different weights
� the bigger weight is deflected less by perturbations (e.g. raindrops)
� the relation is inverse proportional
1
21
12
2
2
12
21
1
1
2
2
1
PPP
aaa
PPP
aaa
P
P
a
a
−
−=
−
−=
=
posi tio
n: w
hole
we
ight
positio
n:
half w
eig
ht
the
ore
tical p
ositio
n
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Mechanical plumb measurement: top of the shaft
bobbin with wire Ø 2mm 800 m wire = 17 kg steel
guide roll
weights 19 x 25 kg
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Mechanical plumb measurement: top of the shaft
determination of the wires
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Mechanical plumb measurement: bottom of the shaft
observation of wires with T 2002
removing weights
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Mechanical plumb measurement: bottom of the shaft
on site analysis
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Results of the optical and mechanical plumb measurements
� plumb measurement of 3 points during each campaign
� comparison of the triangles at the top and the bottom of the shaft:
� mechanical: precision ≈ 5 mm
� optical: precision ≈ 6 mm
� network adjustment:
� tunnel network at the top and the bottom of the shaft
� azimuths of the gyroscope
� mechanical and optical plumb measurements
� network adjustment with optical or mechanical plumb measurements:
� maximal coordinate differences 2 mm
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Height transfer
� vertical electronic distance measurement with TCA2003
� special adapter to fix the reflector under the tripod
� difficulties with ATR due to dripping water. With TCA2003 impossible, with TCRP1201 successful
� the measured distance is exactly the height difference (see gravity measurements)
� precision about 2-3 mm
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Transfer of orientation
methods
double optical plumb measurements in 2 shafts
three-dimensional network
polarized light
gyroscope
inertial measurement technolgy
problems
the 2 shafts are to close, insufficient accuracy
expensive, insufficient accuracy
insufficient accuracy
deviations of the vertical, instrument is dependent of temperature variations
missing experience
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Transfer of orientation
� primary method: gyroscope
� several measurements in different phases of the tunnel construction
� instrument: Gyromat 2000
� independent method: inertial measurement technology
� world premiere
� 2 measurement campaigns: 2004 and 2005
� the direction transfer in Sedrun and especially the independent control is one of the biggest challenges of the whole AlpTransit project
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Measurement with the Gyromat 2000 on the portal pillar of Sedrun
base tunnel
reference-azimuth
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The Gyromat 2000 in the tunnel
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Measurement with inertial technology 2004/2005
� collaboration of geomETH and TU Munich
� positioning the inertial measurement unit (IMU) in the shaft hoisting system in shaft I
� direction transfer to and from the IMU with autocollimation at the top and the bottom of the shaft
� connection to the tunnel network at the top and the bottom of the shaft
� independent direction transfer to control the gyro azimuths
� world premiere! for the first time this technology was used in engineering geodesy for such high precision
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Measurement arrangement
shafthoistingsystem
platform
mirror
mirror
GAP
IMU
tunnel network instrument
βo
αo
top
top
αu
βu
bottom
bottom
ψ
tu = to + βo + αo + ψ – (βu + αu) azimuth:
15
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Animation
�
�
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Situation in the shaft hoisting system
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Inertial measurement unit (IMU)
� 3 acceleration sensors
� 3 laser gyros
� coaxial arrangement
IMU, resolution 0.1 mgon, drift 0.002°/h
laser gyro© K. Foppe
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Arrangement at the top of the shaft
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At the bottom of the shaft
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Team: 3 at the top of the shaft, 3 at the bottom of the shaft
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Results
� direction transfer with the gyroscope: precision ca. 1.3 mgon
� direction transfer with inertial measurement technology: precision ca. 1.5 mgon
� difference of the 2 methods in Sedrun: 2.2 mgon
� an independent control was realised successfully
� significant higher reliability
ETHZ – EG II – Tunnel Surveying I – 22.04.2010
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Gotthard base tunnel: breakthrough results
autumn 2010Faido – Sedrun
33 mm5 mm14 mmjune 2009Erstfeld – Amsteg
21 mm3 mm137 mmoctober 2007Amsteg – Sedrun
12 mm17 mm92 mmseptember 2006Bodio – Faido
distanceheightlateraldateBreakthrough
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Impact of the tunnel construction at the surface
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Extra controls of the dams above the future tunnel
� tunneling works have drainage effects of the rock below different dams
� vertical movements at the surface can not be excluded
� experiences in Switzerland with this topic:
� damages at the dam of Tseuzier in 1978: construction of a sounding tunnel
� height changes above the Gotthard road tunnel: 12 cm
� extra controls of the dams above the tunnel are necessary before, during and after the tunnel construction
� difficult distinction between normal movements (summer – winter, high and low water level in the lakes) and movements due to tunnel construction
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Dams above the Gotthard base tunnel
base tunnel, 500 m.ü.M.
Curnera, Nalps, Santa Maria,1900 m.ü.M.
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Three dimensional view
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Overview measurement installations
� 6 cross-sections of the valleys monitored by 10 automated tacheometer stations
� 100 km precision levelling every year
� 10 permanent GPS-points
Legende: Projektachse Talquerschnitte
Nivellement Strassen Nivellement Stollen
Nivellement Lagerung GPS-Punkt
Oberalp-P
assstr
asse
Val C
urn
era
Val N
alp
s
Lukm
anie
r -
Pass
stra
sse
© swisstopo, Grafik ATG
Campra
Val
Ter
min
e
Sedrun
Disentis
1 km
2.5 km
3.5 km
Ritom-See
So
ndie
rsto
llen
LosgrenzeSedrun / Faido
Legende: Projektachse Talquerschnitte
Nivellement Strassen Nivellement Stollen
Nivellement Lagerung GPS-Punkt
Oberalp-P
assstr
asse
Val C
urn
era
Val N
alp
s
Lukm
anie
r -
Pass
stra
sse
© swisstopo, Grafik ATG
Campra
Val
Ter
min
e
Sedrun
Disentis
1 km
2.5 km
3.5 km
Ritom-See
So
ndie
rsto
llen
LosgrenzeSedrun / Faido
Legende: Projektachse Talquerschnitte
Nivellement Strassen Nivellement Stollen
Nivellement Lagerung GPS-Punkt
Oberalp-P
assstr
asse
Val C
urn
era
Val N
alp
s
Lukm
anie
r -
Pass
stra
sse
© swisstopo, Grafik ATG
Campra
Val
Ter
min
e
Sedrun
Disentis
1 km
2.5 km
3.5 km
Ritom-See
So
ndie
rsto
llen
LosgrenzeSedrun / Faido
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Control network of the Nalps dam
tacheometer positions© swissphoto
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Automatic tacheometer stations: Leica TCA 2003
radio antennas
meteo sensors
ventilation
Photos: Swissphoto
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Measurement concept Nalps dam
high level
middle level
middle level
low level
low level
GPS-points
1 km north of lake
near the dam
south of lake
surrounding area
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Correlation between distances and water level in the lake
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Correlation between temperature and different distances
2002 Curnera Mauer (Mauerpunkte): Dif ferenzen längs zum Tal
-24
-20
-16
-12
-8
-4
0
4
8
12
16
20
24
Dif
fere
nzen
in
[m
m]
-10
-8
-6
-4
-2
0
2
4
6
8
10
12
14
Tem
pera
tur
in [
Gra
d C
]
2010 - 0001
2010 - 2005
2010 - 0002
2011 - 0001
2011 - 2005
2011 - 0002
Temperatur
Vorz eichenkonvention:
Positive Werte zeigen eine
talauswärt ige Verschiebung des -
gemäss Legende - ersten
bezüglich d es zweiten Punktes an.
2010
2011
2002
2007
00010002
2005
18
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Precision levelling campaigns: 100 km every year
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Vertical movements in the area of Sedrun
8 mm / 5 years
reference points
caused by
construction of tunnel and
shaft?
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Syncline above the tunnel
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Profile along the tunnel: Sedrun→Faido vertical movements at the surface
1720
00
1710
00
17
000
0
1690
00
16
800
0
1670
00
1660
00
1650
00
1640
00
1630
00
1620
00
-30
-20
-10
0
10
Vert
ika
lbe
weg
un
g i
m V
erg
leic
h z
u 2
002 [
mm
]
Se
p-0
3
Se
p-0
4
Se
p-0
5
Se
p-0
6O
kt/
No
v 0
6
Se
p-0
7
Se
p-0
3
Se
p-0
4
Se
p-0
5
Se
p-0
6
Okt/
No
v 0
6
Se
p-0
7
0
500
1000
1500
2000
2500
3000
3500
4000
m ü
be
r M
eer
2003
2004
2005
2006
2007
Vortriebsstand
Mauer projiziert
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Ceneri base tunnel: monitoring of the crossing under the A2
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Crossing the A2: monitoring installations
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Vigana
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Vezia near Lugano
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Ceneri base tunnel – 01.04.2010
Ausbruch und Ausbau abgeschlossen
Ausbruch abgeschlossen
Noch auszubrechende Tunnelröhren
Von 39,78 km Tunnel und Stollen sind
7,73 km oder 19,4% ausgebrochen
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Gotthard tunnel Göschenen – Airolo: breakthrough 28.02.1880
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Gotthard base tunnel Amsteg – Sedrun: breakthrough 19.10.2007
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Group picture of the Gotthard base tunnel surveying staff
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Further information
� www.alptransit.ch
� www.bsf-swissphoto.com � Publikationen
� Geomatik Schweiz 6/2006
� Vermessungsanlass zum Hauptdurchschlag im Gotthard-Basistunnel
� 29. Oktober 2010 an der ETH Hönggerberg
� www.gbt-vermessung.ethz.ch (22.04.2010 noch nicht aktiv)
� Geomatik Schweiz 12/2010