Monitoring for underground constructions

Transcription

1 Monitoring for underground constructions VIS Project: Innovatieve corrosiebescherming bij ondergronds bouwen 1 What can happen (below our feet)? Corrosion Cracking Water issues Often linked! soil air Mechanical forces Deformations steel water microbia 2 1

2 Result: Structural integrity affected Reduced operational life Increased maintenance need Liability Over / under designed 3 Follow-up: integrated monitoring 4 2

3 Result: Dashboard for remote follow-up Multiple parameters Cross-correlation Linking with external data Alarms Precipitation (ground) Water level Wind speed and direction Interpretation and understanding 5 Also important Sensor type selection Sensor position Sensor readout (timing/resolution) Sensor connection (fixed to structure, equipotential ) Influences interpretation! 6 3

4 Corrosion 7 Corrosion: Monitoring Multiple techniques available: ER (Electrical resistance) Coupons LPR (Linear polarization resistance) PermaZen Thickness measurement (ultrasonic) Potentials and currents (cathodic protection) Basic question: How much material do I lose / year? 8 4

5 ER: Electrical Resistance 9 ER: Electrical Resistance More corrosion Higher resistance Remaining thickness ( m) Time (a.u.) 10 5

6 ER: Electrical Resistance 11 Coupons Lowtech Weight loss + appearance Cleaning before weighing Not remote: intervention required 12 6

7 LPR: Linear Polarization resistance Exclusively aqueous / liquids Perform potential sweep, record current response 13 PermaZen: Active corrosion of the structure Example in offshore monopile Foundation nr 1 Foundation nr 2 Higher spread Sensors in water: Inert MMO rods 14 7

8 Thickness measurement Ultrasonic thickness Limited sensitivity Positioning critical Takes long before material loss is detected 15 Potentials (CP) / Stray current mapping Night Weekday Weekend day 10 min bins Max Average Min 16 8

9 Cracking 17 Cracking: issues In concrete / grout Can give rise to Facilitated water transport Loss of structural stability Decohesion steel concrete (load-bearing capacity) 18 9

10 Sensor: IntegriZen IntegriZen Based on conductivity at multiple frequencies 19 IntegriZen Water uptake (capillary + microcracks): degradation Single location sensor signal Kinetics wetting / drying = f(microcracks) 20 10

11 IntegriZen Grout electrode signal Function of wind direction and wind speed Damage can be located Position 4: no damage Multiple sensors on single structure Wind direction Wind speed Cracking Microcracks Decohesion Water uptake 21 Water issues 22 11

12 Water issues (unexpected) ingress of water Can result in Extensive corrosion Soil removal Corrosion Concrete cancer Esthetical damage Important to monitor 23 Water level sensors 24 12

13 Water parameters ph Salinity Sulfates Oxygen levels 25 Deformations 26 13

14 Deformations Can be origin or result Of corrosion Of soil movement Steel or concrete Mainly strain / extension, also cracks 27 Deformations: sensor types Foil strain gauge Extensometer VW strain gauge LVDT Fiber optics Crack measuring 28 14

15 Foil strain gauge Continuous Sensitive / small deformations Locate T correction possible Potentially vulnerable, but can be protected In concrete On steel 29 Extensometer Larger distance / deformations No location 30 15

16 Vibrating Wire strain gauge Continuous Sensitive Locate T correction more challenge Potentially vulnerable Complex readout In concrete/grout On steel 31 LVDT (/Displacement) Local Continuous Larger deformations Between structures (relative movement) Different form factors 32 16

17 Acoustic emission On welds / cracks 33 Optical fiber See BBRI (WTCB) slides 34 17

18 For interpretation Read-in / sourcing of additional data Meteo (precipitation, wind direction, water levels, tides ) SCADA and other operational data Continuous + common timestamp with monitored data Proper understanding of phenomena Better remediation plan 35 Examples 36 18

19 Strand anchor Humidity sensor Corrosion activity sensor (ER) Thickness of cover (IntegriZen) Critical: Cable protection / placement 37 Self boring anchor Humidity sensor Corrosion activity sensor (ER) Thickness of cover (IntegriZen) Critical: Cable protection Installation during boring operation? 38 19

20 Self boring anchor Push-in immediately after drilling? 39 Soilmix Corrosion activity sensor (ER) Reference potential ph Stray Currents Can be attached to rebar cage or to (H) profile Additional protection may be required 40 20

21 Sheet piles Corrosion activity sensor (ER) Reference potential Stray Currents Can be attached to sheet preinstallation and protected 41 Diaphragm Wall Normal: Concrete Rebar Cage Onvolledige vulling Incomplete: Result: - Instability - Leakage - Corrosion Solution: Oplossing:4IntegriZen Validate Conductivity4(pre<calibrated) full fill at blind side 42 21

22 Quay E B G F B B B C F D A A: scour sonar (soil movement) B: Strain / extensometers C: Inclination D: IntegriZen E: Water level behind wall F: Temperature G: Corrosion probe (ER) B B 43 Concrete Bridge E C A G B B E A E A E D E C C A: LVDT: relative displacement B: Accelerations (fatigue) C: Strain D: Inclination E: Temperature F: Corrosion probe (ER) G: Acoustic emission (crack growth) F F F 44 22

23 Steel Bridge A: Accelerations (fatigue) B: LVDT: relative displacement C: Surface strain (stresses / fatigue) D: Inclination E: Temperature F: Corrosion probe (ER) G: Acoustic emission (crack growth) EC B F E A CE B D C F E A G CE B F 45 Result Different users, different viewing rights Analysis results Alarm management 46 23

24 Benefits Condition-based maintenance instead of planned maintenance Early warning cheaper repair Long-term follow-up (post construction) Design validation less or more Material used in following constructions Corrosion protection used in following constructions Validating new / innovative materials / designs Risk reduction (financing / insurance) 47 24