DMS

DMS
Lars Harald Blikra & Lene Kristensen, Åknes/Tafjord Monitoring Centre
Mario Lovisolo, Centro Servizi di Geoingegn...
Risk related to large rockslides in Norway

Åknes
Tafjord 1934

Loen 1905 og 1936

Åknes/Tafjord Beredskap IKS
Monitored rockslides
in Norway
Handled by two monitoring
centres funded by
government/NVE,
municipalities and counties:
• ...
Regulations in Norwegain building code
• The population safety needs to be taken care of by realtime monitoring, warning a...
(1) Investigations
• Surface
• Subsurface

(2) Monitoring systems
• Surface
• Subsurface
• Driving mechanisms

Åknes/Tafjo...





Geophysics were possible
Core drillings
Borehole logging – televiewer and other sensors
Borehole displacements

Å...
INSTRUMENTATION
Inclinometer probe – manual readings
?
Long columns with continuous records
Considerations
•
•
•
•
•

Åkne...
• Robust technology
• Leading technology
• Large economic savings in a
long-term perspective
The DMS borehole instrumentat...
Casing

Åknes/Tafjord Beredskap IKS
Method: Differential monitoring system (DMS)

1 m modules

Åknes/Tafjord Beredskap IKS
Differential monitoring system, DMS – “Snake”
Real-time , continuous measurements
Steel
modules
with sensors

Flexible cen...
Example: Åknes

Deep drillings

Åknes/Tafjord Beredskap IKS
SEE ALSO POSTER: GB INSAR
MEASUREMENT AT THE ÅKNES
ROCKSLIDE, NORWAY

Åknes/Tafjord Beredskap IKS
Åknes/Tafjord Beredskap IKS
Deep core drillings – 200 m deep

Åknes/Tafjord Beredskap IKS
N

E

Televiewer image
of the sliding plane

Sliding zone

Åknes/Tafjord Beredskap IKS

S

W

N
2 years of
displacements
2011and 2012:
Direction towards
SW

Sliding plane
2009 - 2013:
• Total of 9 cm
movements on
2 sen...
DMS time series: 49-51 m depth

Åknes/Tafjord Beredskap IKS
Åknes/Tafjord Beredskap IKS
Time line for sensor
at 49-50 m depth.
• Displacement
• Water level
• Temperature

Internal changes/
dynamics of the
rocks...
Lyngseidet

Åknes/Tafjord Beredskap IKS
Aktive back fracture:
20-25 m deep, 2,5 cm/year

Åknes/Tafjord Beredskap IKS
Active movements

Åknes/Tafjord Beredskap IKS
Depth/Size/Volume?

Åknes/Tafjord Beredskap IKS
Rock cores

Åknes/Tafjord Beredskap IKS
Clay in sliding zone: 45 m depth

Åknes/Tafjord Beredskap IKS
Borehole instrumentation to measure movements, temperature and water

Åknes/Tafjord Beredskap IKS
DMS movements at 45/46
m depth:
1th of May – 3rd of October

E

Åknes/Tafjord Beredskap IKS
Time series February – August 2013
May 2013

Åknes/Tafjord Beredskap IKS
Active movements

Åknes/Tafjord Beredskap IKS
Volume: Probably 5-6 mill. m3

Åknes/Tafjord Beredskap IKS
DMS and Real-time warning
• Each sensor have threshold values for displacements
• Can follow directly the critical sliding...
 Norwegian building codes has strong requirements
for monitoring and permanent handling of the EWS
 Subsurface data give...
Important that the geoscientific
community clearly tells the
government what knowledge is
needed for reliable monitoring a...
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Blikra - vajont 2013

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International Conference Vajont2013 - 8 October

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Blikra - vajont 2013

  1. 1. DMS DMS Lars Harald Blikra & Lene Kristensen, Åknes/Tafjord Monitoring Centre Mario Lovisolo, Centro Servizi di Geoingegneria (CSG), Italy Åknes/Tafjord Beredskap IKS
  2. 2. Risk related to large rockslides in Norway Åknes Tafjord 1934 Loen 1905 og 1936 Åknes/Tafjord Beredskap IKS
  3. 3. Monitored rockslides in Norway Handled by two monitoring centres funded by government/NVE, municipalities and counties: • Åknes/Tafjord Beredskap (technical and geological) • Nordnorsk fjellovervåking (technical) Åknes/Tafjord Beredskap IKS CONTENT  Requirements  Subsurface investigations & instrumentation  Åknes and Jettan case  Conclusions
  4. 4. Regulations in Norwegain building code • The population safety needs to be taken care of by realtime monitoring, warning and evacuation • The warning time shall not be shorter than 72 hours and the evacuation time shall be maximum 12 hours • A system for daily continuous monitoring of the conditions, e.g. by measurements of displacements • Independent monitoring instruments and backup communication and power systems • Sufficient technical and geo personnel/competence for safe and reliable monitoring and warning Åknes/Tafjord Beredskap IKS
  5. 5. (1) Investigations • Surface • Subsurface (2) Monitoring systems • Surface • Subsurface • Driving mechanisms Åknes/Tafjord Beredskap IKS
  6. 6.     Geophysics were possible Core drillings Borehole logging – televiewer and other sensors Borehole displacements Åknes/Tafjord Beredskap IKS
  7. 7. INSTRUMENTATION Inclinometer probe – manual readings ? Long columns with continuous records Considerations • • • • • Åknes/Tafjord Beredskap IKS High cost of boreholes Robustness Characterization vs real-time warning Resolution Flexibility
  8. 8. • Robust technology • Leading technology • Large economic savings in a long-term perspective The DMS borehole instrumentation: • Documented to have survived more than 70 cm movements Conventional methods: c. 3 cm Åknes/Tafjord Beredskap IKS DMS
  9. 9. Casing Åknes/Tafjord Beredskap IKS
  10. 10. Method: Differential monitoring system (DMS) 1 m modules Åknes/Tafjord Beredskap IKS
  11. 11. Differential monitoring system, DMS – “Snake” Real-time , continuous measurements Steel modules with sensors Flexible centralizers fixed to the borehole casing Flexible junctions Åknes/Tafjord Beredskap IKS Subsurface LAB: • 2D Inclinometer (0,4 mm resolution) • Pietzometer • Temperature sensor • Digital compass • One systems of 150 m length, total of 304 sensors
  12. 12. Example: Åknes Deep drillings Åknes/Tafjord Beredskap IKS
  13. 13. SEE ALSO POSTER: GB INSAR MEASUREMENT AT THE ÅKNES ROCKSLIDE, NORWAY Åknes/Tafjord Beredskap IKS
  14. 14. Åknes/Tafjord Beredskap IKS
  15. 15. Deep core drillings – 200 m deep Åknes/Tafjord Beredskap IKS
  16. 16. N E Televiewer image of the sliding plane Sliding zone Åknes/Tafjord Beredskap IKS S W N
  17. 17. 2 years of displacements 2011and 2012: Direction towards SW Sliding plane 2009 - 2013: • Total of 9 cm movements on 2 sensors Åknes/Tafjord Beredskap IKS Accumulated total Differential Movement for each individual sensor
  18. 18. DMS time series: 49-51 m depth Åknes/Tafjord Beredskap IKS
  19. 19. Åknes/Tafjord Beredskap IKS
  20. 20. Time line for sensor at 49-50 m depth. • Displacement • Water level • Temperature Internal changes/ dynamics of the rockslide controls the hydrological system and the deformations Åknes/Tafjord Beredskap IKS
  21. 21. Lyngseidet Åknes/Tafjord Beredskap IKS
  22. 22. Aktive back fracture: 20-25 m deep, 2,5 cm/year Åknes/Tafjord Beredskap IKS
  23. 23. Active movements Åknes/Tafjord Beredskap IKS
  24. 24. Depth/Size/Volume? Åknes/Tafjord Beredskap IKS
  25. 25. Rock cores Åknes/Tafjord Beredskap IKS
  26. 26. Clay in sliding zone: 45 m depth Åknes/Tafjord Beredskap IKS
  27. 27. Borehole instrumentation to measure movements, temperature and water Åknes/Tafjord Beredskap IKS
  28. 28. DMS movements at 45/46 m depth: 1th of May – 3rd of October E Åknes/Tafjord Beredskap IKS
  29. 29. Time series February – August 2013 May 2013 Åknes/Tafjord Beredskap IKS
  30. 30. Active movements Åknes/Tafjord Beredskap IKS
  31. 31. Volume: Probably 5-6 mill. m3 Åknes/Tafjord Beredskap IKS
  32. 32. DMS and Real-time warning • Each sensor have threshold values for displacements • Can follow directly the critical sliding zones • Sms thresholds: 1 mm/day • Threshold values for different hazard levels • Trustable and robust system • Little noise compared to surface measurements Åknes/Tafjord Beredskap IKS
  33. 33.  Norwegian building codes has strong requirements for monitoring and permanent handling of the EWS  Subsurface data gives a knowledge platform for early-warning and key data for geological models/volumes needed for evaluation of runout/tsunamis (RISK)  Borehole instrumentation is a vital part of real-time monitoring  DMS instrumentation is a robust in-situ laboratorium: • Direct displacement at sliding planes with directions • Water pressure vs movements • Temperature/permafrost vs movements Åknes/Tafjord Beredskap IKS
  34. 34. Important that the geoscientific community clearly tells the government what knowledge is needed for reliable monitoring and EW Åknes/Tafjord Beredskap IKS

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