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Transcript of We will start shortly…. Detection and localization of sinkholes and soil settlements with...
We will start shortly…
Detection and localization of sinkholes and soil settlements with distributed
sensing
Presented by: Riccardo Belli – PLM Distributed System
Web Seminar
• You should hear my voice through your PC speaker / headset
• You can ask questions using the “Questions” panel on the right of your screen. We will answer:
• In the “Questions” Panel• At the end of the presentation• By email
• Later this week you will receive link to:• Presentation in PowerPoint, PDF and with narration• Datasheets
Contents
• Introduction / motivations to soil settlements
and sinkhole openings Monitoring with
Distributed Fiber Optic Sensors
• Technology
• Application Examples
• Questions and Answers
Sinkhole and soil settlement
Sinkholes, also known as dolines or cenotes,are depressions or holes in the Earth's surface
caused by collapse of either underground minesor karst features, such as caves or cavernsresulting from the chemical dissolution of
carbonate rocks such as limestone or dolomite.Worldwide, sinkholes may vary in size from 1 to600 meters (3 to 2,000 ft) both in diameter anddepth, and vary in form from soil-lined bowls to
bedrock-edged chasms. Sinkholes may formgradually or suddenly.
Sinkhole and soil settlement
• Large Geotechnical critical areas
• Lack of effective monitoring that can provide full / nearly full coverageSENSING EVERYWHERE
• Limited capabilities of conventional sensors, mainly in localize the settlement and cover the critical area
• Limited possibility of predicting sinkhole opening or soil settlement, definition of effective sensors network
• Provide early stage detection and fast reaction
• Increasing safety awareness
• 24 / 7 automatic monitoring and alert triggering
• Remote control
Motivations
Motivations
Traditional sensing
?
Motivations
Anomaly occurence
?
Sensing everywhere
Motivations
Sinkhole & Settlement Monitoring Goals
• Localization of abnormal soil movements• Analysis of sinkhole and soil settlement evolution• Threshold monitoring• Detection of early stage sinkhole and soil settlement• Precise localization over wide areas
SENSING EVERYWHERE• Default prevention
Technology
Distributed Sensing
• Single fiber optic sensor (sensing cable)
• Every segment of sensing cable replaces a discrete
sensor (typically a long gage sensor)
• Provides for location (where?) and magnitude
(how much?) of measurand (average strain and/or
average temperature)
• Complete measurand profile obtained by single
scan
T, ε T, ε
DiTeSt - Brillouin scattering effects
The Brillouin frequency shift B is directly proportional to the acoustic velocity VA, which in
turn is directly related to the material density, which is temperature T and strain dependent.
Scattering medium
Laser, o
Brillouin FrequencyShift:
B = 2nVA /
B(T,) depends ontemperature and
strain
FF
T1
Position [m]
Str
ain
[]
DiTeSt STA-SMA Reading Unit
Distributed Sensor0m
1m 100m
1000m
50km
T1
T2
T2
Position [m]
Te
mp
. [°C
]
DiTeSt ® STA – SMA System
DiTeSt ® STA – SMA System
Measurement range: 0 - 50 km per channel (depending on selected strain sensor)
Spatial resolution: min. 0.5 m (5 ns pump pulse width)
Distance resolution m @ full range: 0.1 m (depending on spatial resolution)(sampling rate – 1 point every 0.1 m)
Number of locations: up to 100’000 distance points
Acquisition time: minutes (typical)
Number of channels: 2
Multiplexer: from 4 up to 20 channels
DiTeSt SMARTprofile Sensor
• 2 fibers for strain sensing and 2 for interconnection (if applied for settlement and sinkhole monitoring)
• Encapsulation in a Polyethylene PE profile
• Strain range: 1% = 10000 = 10 mm/m
• Direct soil or geo-textile embedding
• Optical losses ~ 1.0 dB/km
DiTeSt SMARTube Sensor
• Improved and reliable design
• Dimensions: 5.34 mm outer tube, 2.8 mm inner tube
• Optical losses ~ ≤ 2.0 dB/km
• Good mechanical reliability
5.34
mm
2.8 mm
• Management of distributed measurement data
• Strain measurement analysis of single and multiple
sensors
• System Status Management
• Automatic and schedule measurements 24 / 7
• Alarm triggering
• Warnings based on threshold and rate conditions
• Voice message, e-mail, SMS, acknowledge via SMS
• Remote connection and assistance
• Data display on maps
DiView Software TT
Settlement working principle
• Buried distributed strain sensor over the selected critical area – sensing everywhere with single cable
• Sinkhole or soil settlement induces strain over the sensing cable by stretching the fiber
• DiTeSt STA-SMA detects strain variations / evolution and localize it on the distributed sensor
• DiView data management software visualizes the anomaly on a map
• DiView data management software automatically triggers an alert and send mail or sms message at selected recipient
Applications examples
Polytect FP6 - EU project
0.5 m
5 m
4 m
0.4 m
Sand
Controlled Settlement
area
Displacement meter (LVDT)
“Bath”
SensorGeotextile
Polytect FP6 - EU project
Inflating balloon
Vertical displacement meters
Polytect FP6 - EU project
Zero condition Simulated settlement
Polytect FP6 - EU project
Typical differential analysis plot
Polytect FP6 - EU project
SMARTprofile, F1
-1000
0
1000
2000
3000
4000
5000
6000
7000
8000
9000
13 14 15 16 17 18 19 20 21 22
position [m]
Ave
rag
e st
rain
[ ]
4.09 mm 42.17 mm
58.67 mm 64.97 mm
76.68 mm 80.82 mm
90.32 mm 90.32 mm
90.32 mm 90.32 mm
93.26 mm 96.80 mm
107.38 mm 115.41 mm
119.67 mm 130.95 mm
133.38 mm 139.76 mm
Con
trolled
sett
lem
en
t
Settlement zone
5 m
SMARTprofile F1
y = 66.98x - 303.61
R2 = 0.97
-1000
0
1000
2000
3000
4000
5000
6000
7000
8000
9000
0 10 20 30 40 50 60 70 80 90 100 110 120 130 140
Vertical settlement [mm]
Ave
rag
e st
rain
in
set
tlem
ent
po
int
(co
ord
inat
e 17
.91m
) [
]
Bigger settlement Hiher strain in sensor
Polytect FP6 - EU project
Polytect FP6 - EU project
Quay-wall monitoring project
• DiTeSt STA-SMA • 2 SMARTprofile monitoring lines, 580 m each• DiView 24 / 7 automatic software• Soil stability • Abnormal de-soilment detection and localization
Quay-wall monitoring project
• SMARTprofile Distributed Strain Sensor directly embedded into soil during construction phases with the aim to detect abnormal de-soilment and analyze the evolution of soil settlement.
• Continuous automatic monitoring from the construction to the operation.
• Effective detection and localization of settlement area and of abnormal de-soilment during early operational phases.
DiView software GUI
Quay-wall monitoring project
De-soilment
area
Cable maintenance in settlement area
Quay-wall monitoring project
Sinkhole monitoring project
Hutchinson – Kansas – USASubsidence sink-hole monitoring projectJanuary 2010
Sinkhole monitoring project
A total of 4 km of Strain Distributed Sensor dicertly buried into soil
Sinkhole monitoring project
Digging of the trench were the sensor is deployed
Sinkhole monitoring project
Site operations
Site quality check
Sinkhole monitoring project
Site pulling test @ different locations
Sinkhole monitoring project
DiView software GUI
Project Pubblications
Smart Textiles for SHM of Geostructures and Buildings
Localization of instability zones in levees, landslides, sinkholes and tunnels with
distributed optical fiber sensors
Salt cavern monitoring system for early warning of sinkhole formation
Conclusion
• Soil settlement evolution and sinkhole formation monitoring
• Detection and localization of soil settlement and sinkhole formation over long distances
• Detection and localization of sinkhole formation at early stage
• Reliability in demanding environments
• Extended measurements range
• Cost effective
• On-line permanent monitoring
• Powerful and versatile software for data management and intelligent alerts
Pipeline Integrity Monitoring
Thank you for your attention
For more informationwww.roctest-group.com
Thank you for your attention