Increasing Dam Safety and Integrity by using Distributed Fiber Optic - - PowerPoint PPT Presentation

A company of the Brugg Group

Increasing Dam Safety and Integrity

by using Distributed Fiber Optic Sensing ( DFOS)

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Motivation for Distributed Fiber Optic Sensors (DFOS)

• The demand to continuously measuring and diagnosing the structural health of

wide and long structures, drives the globally strong growth of systems with distributed fiber optic sensors (DFOS).

• Required measures: Temperature, strain, pressure, humidity, acoustics and vibration

(seismic) at any point along the optical fiber sensor.

• Detecting cracks in concrete before they become visible, may help to prevent structural

collapse.

• Distributed Fiber Optic Sensors, combined with the evaluation systems are generating

and picturing (even in 3d) the required and reliable information to take appropriate decisions and measures, to manage and limit threats and danger.

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Threats to a safe dam operation

• Structural health
• Statics, anchorage, material integrity, impermeability, integrity & performance

management of high pressure water pipes, etc.

• Ageing
• cracks, fatigue, material deterioration, anchorage, environment
• Leakage
• due to ageing, cracks, fatigue, soil deformation, seismic activities, etc.
• Soil deformation and interaction to dam wall
• settlement of soil, land slide, permafrost, anchorage instability

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Threats to a safe dam operation, cont.

• Seismic activities
• Cracks, static instability, strain and fatigue, anchorage instability, physical damages
• Exceeding maximum water level
• due to high water pressure, excessive rain fall, land slides
• Sabotage and obstruction, third party intrusion
• Prohibited areas, control room, turbines, dangerous zones, etc etc..

Methods how to prevent the threats

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Fatalism: Ignore the risks, no up-front costs, no maintenance costs no budget debate high personal risk for people in duty Fatalism: Ignore the risks, no up-front costs, no maintenance costs no budget debate high personal risk for people in duty Physical Inspection: costly due to manpower & time consuming, may be unreliable, just a snapshot, no continuous monitoring possible Physical Inspection: costly due to manpower & time consuming, may be unreliable, just a snapshot, no continuous monitoring possible Active Point Sensor: proven technology, well priced, maintenance intensive, cables for data and power supply required, finite reading points Active Point Sensor: proven technology, well priced, maintenance intensive, cables for data and power supply required, finite reading points DFOS, Passive Sensor fast & easy installation, state of the art technology, low maintenance, remote & real time monitoring, infinite reading points DFOS, Passive Sensor fast & easy installation, state of the art technology, low maintenance, remote & real time monitoring, infinite reading points

A company of the Brugg Group

20 years experience in Distributed Fiber Optic Sensing

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DFOS for improving of Dam Safety and Integrity

DFOS for higher dam safety and integrity in every day‘s operation

• hydro power dams and
• dykes and natural dams

Also used for mining, nuclear power, fire safety, border & perimeter control, oil & gas, pipeline, railway, geotechnics, etc.

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Fields of application with fiber optics

Multi- or single- mode optical fiber as sensor 1-2m pulse of light Backscattered light provides measurement point every 1-2m Measurements all along up to e.g. 50km fiber = 50,000 sensors at 1m-resolution

Measuring method based of back-scattering principles

Interrogator Unit Interface to Control Center

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Measuring method based on back-scattering principles

The precision of measurements is an interaction of 4 parameters

• spatial resolution (in cm or m)
• time of measurement (in min.)
• distance to monitor (in m or km)
• measurement accuracy

the choice and definition of above 4 parameters represent a trade-off since they interact with each other

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Technologies used: Optical Time Domain Reflectometry (OTDR)

At the core of each of these technologies is the technology known as Optical Time Domain Reflectometry (OTDR) which was originally developed for the telecommunication industry

Distributed FO Sensing – measuring, detection and localization

Temperature Tension/Strain Vibration* Acoustic Pressure* Chemical elem

ire detection (Tunnels) rocess- & Power-

• nitoring (AC & DC

ransmission) eakage detection for ipelines, dams and mbankments based on emperature differential of edia and ambient ining and Oil & Gas elling ygrometry in the soil agriculture) Structural monitoring of long critical infrastructures as tunnels, dams, dikes bridges, ropes, pipes, etc. Rail track- and paving Monitoring Mining and Oil & Gas welling Detection of buckling of drilling pipes (Oil-welling) Geo-Technology (hang sliding, etc.) Process-monitoring and industrial applications Seismic Applications Perimeter and border control Structural monitoring of long critical infrastructures as tunnels, dams, dikes bridges, ropes, pipes, etc. Leakage detection in Pipelines and Pipes Intrusion, perimeter and border control Structural monitoring of long critical infrastructures as tunnels, bridges, ropes, pipes, etc. Seismic applications Monitoring Mining and Oil & Gas welling Flow measuring Leakage Detection in pipelines Oil wells monitoring Leakage-Detection Hygrometry CO2-measuremen

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Temperature and humidity sensing: DTS for Dam and Dyke applications

Raman scattering provides the temperature profile along the entire fiber length Common applications:

• Leakage (using heated sensing

cables)

• Temperature compensation: for strain

measurements (since temperature- changes induce strain)

• Concrete curing (temperature

monitoring during construction)

• Seasonal temperature load cycles
• Sediment level in retention basins

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Strain Sensing: DTSS for Dam & Dyke applications

Brillouin scattering measures strain and temperature variations along fibers with a length >50km with a spatial resolution <1m range Applications:

• Structural health: Statics, anchorage,

material and wall integrity

• Ageing: monitoring weakening and

deterioration of a dam wall

• Event monitoring: data’s before and

after event available

• DTSS: humidity and leakage with

“heatable” cables

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Acoustic and vibration: DAS and DVS for Dam and Dyke applications

DAS systems are advanced variants of Optical Time Domain Reflectometers (OTDR) that monitor the coherent Raleigh back-scattering. Applications:

• Leakage: in dam walls, dykes,

pressure pipes

• Cracks: in dam walls, anchorages
• Vibration: e.g. from turbines
• Seismic activities: earthquakes, soil

vibrations

• Third party intrusion (remote):

perimeter, control room, turbines

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Installation and mounting of DFOS cables

Installation methods are well known from telecoms and data-communications Applicable for new facility constructions and for retrofit Coverage of

• single-
• multiple- and
• combined- (DTS/DTSS/DAS)

segments Installation accessories

• Soil and wall anchors,
• pre-lead fixtures,
• sensor cable terminations loops

Implementation of FOS to strucural health monitoring

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Consequences of incorrect choice of sensing cables

Mistake Effect wrong choice of fiber for temperature sensing fiber breaks or incorrect measurement results wrong choice of fiber and cable for strain sensing incorrect result and / or possible fiber / cable break wrong choice of cable construction for acoustic sensing inaccurate result of measurement bad choice of sensor poor or even wrong results, high risk due to over- confidence about safety & integrity

Choose the right fiber and cable design for your application

Poor sensors might give poor results, generating eventually false safety feelings in situations, where things might run out of control !

What customers experience:

• Customers try to use just optical fiber

cables for telecomm and data transmission.

• This might work perfect in some

cases.

• In some cases it partly fails.
• In some cases it is a disaster.

The problem is recognized after the installation > big effort to solve it.

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One mistake often made

What is the reason behind:

• Telecom and data cables are not
• ptimized for sensing.
• Important parameters are not

supervised in the QSP.

• Regarding the sensing application the

quality of such cable is not stable.

• The sensitivity differs between lots

and even over the length of a cable. Hence, use specialized sensing cables!

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DFOS applications beside dam and dyke monitoring

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• One technology allows to measure

several types of events and covers all mayor applications critical for dam and dyke safety

• The choice / selection of the right sensing

cable is of utmost importance since it is the heart of any FO monitoring system. Incorrect choice will lead to false safety & integrity information

• User friendly GUI (2D/3D) facilitate easy
• perations and monitoring

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Conclusions

• Cost efficient solution:
• passive system (no power supply, low

maintenance), easy installation

• infinite number of reading points
• remote and continuous monitoring
• suitable for long distance and wide

areas

• DFOS technology is successfully

deployed in many other applications

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Projects with DFOS deployed

• Riding Wood Dam England
• Digley Dam England
• Dams/Dykes in France near Avignon and on Corsica
• Kadamparei Dam / India (with integrated leakage detection sensing cable in geo-

membrane seal)

• Servelar Dam / India (with integrated leakage detection sensing cable in geo-

membrane seal) Ongoing:

• Upper Bhavani Dam / India (tender closed for DFOS leakage detection, offered;

contract not signed yet)

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Latest News: Dam Collapse Risk in USA provokes evacuation of thousands of citizens

For more information

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Brugg Cables Andrea Fasciati Head FO Sensing and Mobile Applications Phone: +41 (0)56 460 33 63 Mobile: +41 (0)79 483 16 01 Mail: andrea.fasciati@brugg.com Brugg Cables Andrea Fasciati Head FO Sensing and Mobile Applications Phone: +41 (0)56 460 33 63 Mobile: +41 (0)79 483 16 01 Mail: andrea.fasciati@brugg.com

Thank you very much for your kind attention!