Innovation in geotechnical instrumentation to realize ...
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Innovation in geotechnical instrumentation to realize performance based design
Kenichi SogaUniversity of California-Berkeley
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Acknowledgement
• GeoVirgina Organizing Committee and Qamar Kazmi
• University of California, Berkeley – PhD students and post-docs
• University of Cambridge, Cambridge Centre for Smart Infrastructure and Construction – PhD students and Researchers
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Examples of distributed strain/displacement sensors
Distributed fiber optics - Embedded sensor for life-long monitoring• Fibre optics – 30-100• Fibre optics – 0.03-0.1 mm resolution (for 1 m gauge length)
Computer Vision and LIDAR• Fixed system – 0.1 mm resolution• Not Fixed system – 3-5 mm resolution
WSN – Continuous monitoring at difficult-to-access sites• Wisen• Utterberry – sub millimeter resolution
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“Value” as a tool
Value = Product(what it claims it will
do)
Product(what it claims it will
do)+
Confidence in delivery
(do I believe it will work?)
Confidence in delivery
(do I believe it will work?)
“Innovations have more chance of adoption if their benefits are mapped” Dr Keith Bowers, London Underground Limited
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118 km from east to west37 stations9 new stations (8 sub-surface)Increase London's rail-network capacity by 10%
Crossrail – New London Underground Line in London
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Monitored Section of the Royal Mail TunnelCrossrail – Liverpool Street Station – C510
Monitored SectionCrossrail Platform Tunnel Excavation
Bloomfield Box Excavation
After Crossrail
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How Big Is It?
≈ 2.74 m
≈11 m
≈6 m
Constructed: 1917 - 1923
Suspended: 2003Made of cast iron
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Fixed support
Tunnel lining
Monitoring area
Camera
Site Overview Camera setup
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Low frequency motion
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Bending Mode
Shearing Mode
Matthew Wilcock
Arup – M. Devriendt
Bending or Shearing?
(After Attewell, 1986)
Smax
Longitudinal Settlement
Radius of Curvature
Radius of Curvature
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2009
2012
2015
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Shear LPDT Orientation
Expected settlement profile
New Tunnel
Compressive (-ve) when ring nearest tunnelling approach shifts downward with respect to neighbouring ring!
Data for these sensors above sign reversed in
data processing.
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Layout of Sensors & Location of Sensors 11, 34-40
Data presented
2881@ Node 11
2940@ Node 40
29.5m
New Tunne
l
120 Wireless Sensors to monitor movements of 60 joints
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Wilcock
Pilot tunnel
Main tunnel
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Bond Street – LUL Station
Royal Mail Tunnel
Passenger Adit
Instrumented Section (35m)
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Longitudinal crossing Transverse crossingBending > Shearing Shearing > Bending
The two case studies show that the cast-iron tunnels are more tolerable to bending (i.e. can accommodate smaller Radius of Curveture (ROC))
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• Distance range ≈10-30km• Readout resolution = 0.05m• Gauge length resolution = 0.2-1m• Strain Resolution = 10-30me
Distributed Sensing providing “Continuous Strain/temperature/vibration Profile” along the fibre optic cable
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Frequencyshift 0
RayleighBrillouin Brillouin
RamanRaman
B B
,T,T
T
0
Backscattered spectrum
1. Send light through the fibre and detect the back scattered light2. Identify the location of back scattering from the time interval3. Measure Frequency shift due to strain (ΔF)4. Translate ΔF to strain: ε = f(ΔF)5. Obtain the strain profile: ε(x) over the whole length of the cable
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Sensing cables
(a-d) Strain/acoustic sensing(e-f) Temperature sensing
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Fujikura ReinforcedFibre Optic CableRobustness
27
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CH5 CP2CP1
Sprayed concrete liningPerformance during cross passage opening
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Tunnel liningBending and axial performance during construction and in long term
-1000.0
0.0
1000.0
2000.0
3000.0
4000.0
5000.0
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9000.0
0.0 100.0 200.0 300.0
Axia
l For
ce (k
N/m
)
Bending Moment (kNm/m)
Capacity limit
Muir Wood Full Slip
Muir Wood FullBondDuddeck Full Slip
Duddeck Full Bond
Joint check - MaxloadJoint check - MaxdeflMuir Wood Full Slip+point loadsMuir Wood FullBond + point loadDuddeck Full Slip +point loadDuddeck Full Bond+ point loadSegment 1
Segment 2
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In January this year, New York Governor Cuomo announced a plan to prevent the 15-month-long L-train shutdown set to begin in April.
The Canarsie Tunnel, which opened in 1924, has shown deterioration after flooding from Hurricane Sandy in 2012.
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A pile loading test…
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A building construction at the Isle of Dog, London
Loizos Pelecanos Duncan Nicholson
River Terrace DepositsLambeth Group
Thanet Sand
Chalk
Made Ground / Alluvium
Large diameter piles - 2.4m dia.Very deep - avoid tunnels ( 25m into Chalk)
LU tunnel
Thick raft span over tunnels
LU tunnel
Musa Chunge Cedric Kechavarzi Vivien KwanEcho Ouyang
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www.loadtest.com
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1.5m
Made Ground
Thanet Sand
River Terrace DepositsLambeth Group
Alluvium
Chalk
Sister Bars
Osterberg Cells
2 fibre optic cables
51m
6m
7m
Level 1
Level 2
Level 3
Level 4
Level 5
Level 6
• Diameter = 1.5m• Length = 51m• Osterberg‐cell• Load up to 31MN
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No disturbance to actual construction operations
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Conventional Strain Gauge System
Distributed FO system
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Layer 1
Layer 2
O-Cell
PileLoad distribution
CompressionFriction
DownUp
Mechanism of O-cell testing
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• Strain gauges
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-5
0
50 200 400 600 800 1000
LEVE
L (m
OD
)
STRAIN ()
Strain gauges
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• Strain gauges
• Extensometers
• DFOS
-1000-800-600-400-2000-40
-35
-30
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-15
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0
50 200 400 600 800 1000
CHANGE IN CABLE STRAIN ()
LEVE
L (m
OD
)
STRAIN ()
Strain gauges
DFOS data
DFOS trend
Axial strain Instrument comparison
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Axial strain Different FO cable comparison
0
5
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35
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45
50
-800 -600 -400 -200 0
Dep
th, z
[m]
Axial strain, ε_a [με]
P = 25.66MN
Cable S-3-1
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Axial strain Different FO cable comparison
0
5
10
15
20
25
30
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40
45
50
-800 -600 -400 -200 0
Dep
th, z
[m]
Axial strain, ε_a [με]
P = 25.66MN
Cable S-3-1
Cable S-3-2
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Axial strain Different FO cable comparison
0
5
10
15
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25
30
35
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45
50
-800 -600 -400 -200 0
Dep
th, z
[m]
Axial strain, ε_a [με]
P = 25.66MN
Cable S-3-1
Cable S-3-2
Cable S-4-1
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Axial strain Different FO cable comparison
0
5
10
15
20
25
30
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45
50
-800 -600 -400 -200 0
Dep
th, z
[m]
Axial strain, ε_a [με]
P = 25.66MN
Cable S-3-1Cable S-3-2Cable S-4-1Cable S-4-2
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-40
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0
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0 0.01 0.02 0.03 0.04
Elev
atio
n [m
]
Vertical displacement, u [m]
Vertical Displacement Profiles
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Load (MN)
Dis
plac
emen
t (m
m)
Load (MN)
Load (MN)
Dis
plac
emen
t (m
m)
Load (MN)
Load (MN)
Dis
plac
emen
t (m
m)
Load (MN)
Top of O-cells
Level 2
Level 3
Level 4
Level 5
Level 6(highest)
Fibre optic integrated strain
Extensometers
Displacements are relative to the top of the pile
Small displacement
Very small displacement
Top of O-Cell
Level 2
Level 3
Level 4
Level 5
Level 6
Extensometer
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Construction can be challenging alignment concrete quality and
placement soil collapse
Visible inspection not possible
Repair and rework is very difficult
Not all anomalies are defects/detrimental
FHWA‐NHI‐10‐0161.
PROBLEMS WITH PILE CONSTRUCTION
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SoilPile
Find the pile radius which match the temperature profile (20 x 4 x 50 = 4000 data sets)
Source of concrete heating
?
Rui Yi Cedric Kechvarzi
1
2
3
4
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0
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th(m
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Fibre optics
Potential for Whole-life Management?Construction Quality Control Real Loading Performance
Future Proofing (EQs, nearby constructions..)
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Deployment of Post Grouting Technique to improve Drilled Shaft End-Bearing Resistance
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Tina Schwamb
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Thames Tunnel
Abbey Mills Pumping station(Captures 39 million tonnes of sewage a year)
Beckton sewage treatment plant
(Schwamb et al., 2014)
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Made Ground
River Terrace DepositsAlluvium
London Clay
Lambeth Group
Thanet Sand
Chalk
70m
30m• Abbey Mills shaft:
– 30m ext. diameter– 70m deep
• Diaphragm walls:– 20 panels– 1.2m thick– 84m deep
Shaft F Details
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Schwamb et al. 2013
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Clough and O’Rourke (1990)Peck (1969)
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Circular shafts“plane strain” shafts
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0
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0 20 40 60 80
Settl
emen
t [m
m]
Distance from shaft wall [m]
New & Bowers (1994)Study at Heathrow shaft ofD = 11 m, H = 26 m
H = shaft depthd = distance from shaftS = settlement = 6 x 10‐4 (empirical factor)
0
2
4
0 5 10
Measured settlement:dwall constructionexcavation
New & BowersH = 70 m = 6 x 10‐4 (0.06%) S/H < 0.005%!
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• Reference Design PLAXIS analysis – 7mm
• Reference Design – modified New & Bowers – 13mm
• Hard to justify approach taken without any empirical data
• Potential cost and risk implications Tideway Tunnel
Original design considerations
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Bendingstrain
5.2mm
1.2mm
6.1mm
Strain cable
Temperature cable
Diaphragm walls Joints between panels Reduced cirumferential
stiffness???
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Monitoring Scheme
Bendingstrain
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Made Ground
River Terrace Dep.Alluvium
London Clay
Lambeth Group
Thanet Sand
Chalk
-1 0 1 -1 0 1 -1 0 1 -1 0 1
-2 0 2
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Dep
th [m
bgl]
Inc. Curvature [10-4 m-1]
Inc. BM [MNm]
Fibre OpticPanel P15Panel P20PLAXIS
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150Diaphragm wall
6mbgl
24mbgl
Fully constrained / No drainage
Not constrained / Drainage
14.45
2D axisymmetric mode
Mohr‐Coulomb soil model
Wall: concrete C50/60 E = 37 GPa(short‐term) thickness = 1.2 m
Wall installation effects are considered with reduced K0values (WIP)
For comparison use serviceability limit state (SLS) results
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]
-1 0 1-90
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-1 0 1-90
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Dep
th [m
bgl]
Inc. Curvature [10-4 m-1]
Fibre OpticPanel P15Panel P20PLAXIS
-0.5 0 0.5 -0.5 0 0.5 -0.5 0 0.5 Comparison:FLAC (MC)FLAC (Adv)FO P15FO P 20
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Other soils above Chalk
Chalk
FLAC modelSoil models
***************************
Elements yield in shear
Mohr Coulomb for CHALK:K = 1000 MPa | G = 600 MPa | E = 1500 MPa ’ = 35ᵒ | c’ = 20 kPa
Other soils above Chalk
Chalk
Hoek‐Brown model for CHALK:K = 1000 MPa | G = 600 MPa | E = 1500 MPaAdditional Hoek‐Brown constants
Elements elastic
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FLAC modelSoil models
-5 0 5-90
-80
-70
-60
-50
-40
-30
-20
-10
0
-5 0 5-90
-80
-70
-60
-50
-40
-30
-20
-10
0
-5 0 5-90
-80
-70
-60
-50
-40
-30
-20
-10
0
-5 0 5-90
-80
-70
-60
-50
-40
-30
-20
-10
0
-5 0 5-90
-80
-70
-60
-50
-40
-30
-20
-10
0
Dep
th [m
bgl]
Lateral wall movement [mm]
Comparison:FLAC (MC)FLAC (Adv)Inc P10Inc P 20
o Low cohesion = 20 kPa in chalk to be on ‘safe side’
o For the wall this had the opposite effect:o Stiffer soil causes sharper bulge o Shaper bulge means more
localised bending
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FLAC modelWall stiffness
-2 0 2-90
-80
-70
-60
-50
-40
-30
-20
-10
0
-2 0 2-90
-80
-70
-60
-50
-40
-30
-20
-10
0
-2 0 2-90
-80
-70
-60
-50
-40
-30
-20
-10
0
-2 0 2-90
-80
-70
-60
-50
-40
-30
-20
-10
0-1 0 1
Dep
th [m
bgl]
Inc. Curvature [10-4 m-1]
Inc. BM [MNm]-1 0 1 -1 0 1 -1 0 1
Comparison:FLAC (37 | 37)FLAC (26 | 26)FLAC (37 | 18.5)FLAC (37 | 3.7)FO P15FO P 20
Stiffness in vertical and radial direction [GPa]Stiffness in circumferential direction [GPa]
FLAC (37 | 3.7) overpredicts here
FLAC (37 | 3.7) is approx. right here
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Northern Line Extension Project
Thermal Integrity FO monitoring of 100 Panels and 74 Piles, replacing other methods such as sonic logging.
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Prof Tom O’RourkeDr Brad Wham
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Elizabeth tunnelLos Angeles Department of Water and Power
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American River Levee Upgrade Project
• Sacramento Metropolitan area remains one of the most at risk areas for flooding in the United States.
• Levees constructed in the previous flood control project (1850-1950), Sacramento River Flood Control Project, were constructed of poor materials
• Flows in either the American or Sacramento Rivers will probably stress the network of levees to the point of failure.
FO Monitoring of cement bentonite cut-off wall, currently upgraded.
US Army Corps of Engineers
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51 km Smart TunnelSingapore’s Deep Tunnel Sewerage System (DTSS)
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Smart Road Corridors by Meso-Scale In-PavementDistributed Infrastructure Sensing
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Alicia
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Best Practice Guides for Monitoring Civil Infrastructure
Distributed Fibre Optics Sensing Wireless Sensor Networks
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Summary• Innovation in sensors as part of Internet of Things
– Exciting opportunities for Geotechnical Engineering to understand the real performance of infrastructure and construction.
• For example, distributed fibre optics (especially embedded) can give useful strain data that no other sensors can give.
• Monitoring system should be an integral part of the construction package– Quality Control– Maintenance– Reuse
• This leads to Performance-design, construction and maintenance.
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Thank you