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

Increasing Dam Safety and Integrity by using Distributed Fiber Optic Sensing ( DFOS) A company of the Brugg Group

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. 2

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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 4

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.. 5

Methods how to prevent the threats Fatalism: Fatalism: Physical Inspection: Physical Inspection: Active Point Sensor: Active Point Sensor: DFOS, Passive Sensor DFOS, Passive Sensor Ignore the risks, Ignore the risks, costly due to manpower costly due to manpower proven technology, well proven technology, well fast & easy installation, fast & easy installation, no up-front costs, no up-front costs, & time consuming, & time consuming, priced, maintenance priced, maintenance state of the art state of the art no maintenance costs no maintenance costs may be unreliable, just a may be unreliable, just a intensive, cables for intensive, cables for technology, low technology, low no budget debate no budget debate snapshot, no continuous snapshot, no continuous data and power supply data and power supply maintenance, remote & maintenance, remote & high personal risk for high personal risk for monitoring possible monitoring possible required, finite reading required, finite reading real time monitoring, real time monitoring, people in duty people in duty points points infinite reading points infinite reading points 6

20 years experience in Distributed Fiber Optic Sensing A company of the Brugg Group 7

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. 8

Fields of application with fiber optics 9

Measuring method based of back-scattering principles Measurements all along up to e.g. 50km fiber = 50,000 sensors at 1m-resolution Interface to Control Center Multi- or single- mode optical fiber as sensor Interrogator Unit Backscattered light provides measurement point every 1-2m 1-2m pulse of light

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 11

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 12

Distributed FO Sensing – measuring, detection and localization Temperature Tension/Strain Vibration* Acoustic Pressure* Chemical elem ire detection (Tunnels) Structural monitoring of long Process-monitoring and Leakage detection in Flow measuring Leakage-Detection critical infrastructures as industrial applications Pipelines and Pipes rocess- & Power- Leakage Detection in Hygrometry tunnels, dams, dikes onitoring (AC & DC Seismic Applications Intrusion, perimeter and pipelines CO2-measuremen bridges, ropes, pipes, etc. ransmission) border control Perimeter and border Oil wells monitoring Rail track- and paving eakage detection for control Structural monitoring of long Monitoring ipelines, dams and critical infrastructures as Structural monitoring of long mbankments based on Mining and Oil & Gas tunnels, bridges, ropes, critical infrastructures as emperature differential of welling pipes, etc. tunnels, dams, dikes edia and ambient Detection of buckling of bridges, ropes, pipes, etc. Seismic applications ining and Oil & Gas drilling pipes (Oil-welling) Monitoring Mining and Oil & elling Geo-Technology (hang Gas welling ygrometry in the soil sliding, etc.) agriculture)

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 14

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 15

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 16

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 17

Implementation of FOS to strucural health monitoring

Consequences of incorrect choice of sensing cables Choose the right fiber and cable design for your application 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 inaccurate result of measurement sensing bad choice of sensor poor or even wrong results, high risk due to over- confidence about safety & integrity Poor sensors might give poor results, generating eventually false safety feelings in situations, where things might run out of control ! 19

One mistake often made What customers experience: What is the reason behind:  Customers try to use just optical fiber  Telecom and data cables are not cables for telecomm and data optimized for sensing. transmission.  Important parameters are not  This might work perfect in some supervised in the QSP. cases.  Regarding the sensing application the  In some cases it partly fails. quality of such cable is not stable.  In some cases it is a disaster.  The sensitivity differs between lots and even over the length of a cable. The problem is recognized after the installation > big effort to solve it. Hence, use specialized sensing cables! 20

DFOS applications beside dam and dyke monitoring 21

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Conclusions  Cost efficient solution:  One technology allows to measure several types of events and covers all  passive system (no power supply, low mayor applications critical for dam and maintenance), easy installation dyke safety  infinite number of reading points  The choice / selection of the right sensing  remote and continuous monitoring cable is of utmost importance since it is  suitable for long distance and wide the heart of any FO monitoring system. areas Incorrect choice will lead to false safety &  DFOS technology is successfully integrity information deployed in many other applications  User friendly GUI (2D/3D) facilitate easy operations and monitoring 23