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Reservoir bank slope in Laxiwa
Hydropower Station, China
Dexuan ZHANG, Gonghui WANG
Shanghai Jiao Tong University, China
D...
Laxiwa Hydropower Station

Laxiwa dam: a hydropower station on the upper reach of
Yellow River. Guide County, Qinghai prov...
Laxiwa Dam: 2nd cascade hydropower
Height: 250 m
Crest length: 460 m
Capacity :1.08 billion m3

Active capacity: 0.15 bill...
Laxiwa Dam
Guopu unstable slope

Oct. 2001: Construction started
Mach 2009: Impundement
May 2009: Power generation
July 2009: slope d...
500m

700m
2452m

2254m

50°
Topography and Geology
Deformation on the head cliff
Deformation on the slope
1989

March 2010

May 2013
Slope deformation by remote sensing

1.interferometric synthetic aperture radar (INSAR)
ALOS PALSAR image list

2. Optical...
Results from INSAR Analysis
Before impoundment:
Nov. 9, 2007-June 10, 2008
< error (10cm)

After impoundment:
2009-12-14~2...
Optical imagery analysis (ALOS PRISM)
 Imageries at two differing periods were processed
 In case of no/small deformatio...
Optical imagery analysis (ALOS PRISM)
After Impoundment:
2008-07-01(before)
~2009-04-03(after)

No change in gray value

N...
Deformation after impoundment

2009-04-03 ~ 2010-05-22
Most part of the slope are in gray color
Max displacement: 3 pixels...
View from Google Earth
Summary
InSAR data: Deformation before the impoundment was very
small.
ALOS PRISM: No obvious deformation during the perio...
What is
happening
now?
Landsliding monitoring
Landsliding monitoring
Countermeasures now
Surficial displacement monitoring system:
GPS + standard survey
290m

750
m
Deforming
on the
upper
surface
Countermeasures now
Inside the deforming mass
Survey tunnel + Vertical boring and monitoring
Sliding surface inside the tunnel
What is happening now?
What we are doing now
Seismometers
What we are doing now
Shear behavior of the sliding surface

Samples
Thanks
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9oct 3 wang1-reservoir bank slope

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9oct 3 wang1-reservoir bank slope

  1. 1. Reservoir bank slope in Laxiwa Hydropower Station, China Dexuan ZHANG, Gonghui WANG Shanghai Jiao Tong University, China DPRI, Kyoto University, Japan
  2. 2. Laxiwa Hydropower Station Laxiwa dam: a hydropower station on the upper reach of Yellow River. Guide County, Qinghai province, 134 km far from Xining, captical city of Qinghai Province
  3. 3. Laxiwa Dam: 2nd cascade hydropower Height: 250 m Crest length: 460 m Capacity :1.08 billion m3 Active capacity: 0.15 billion m3 Power Generation: (6×70)4.20 Million kW
  4. 4. Laxiwa Dam
  5. 5. Guopu unstable slope Oct. 2001: Construction started Mach 2009: Impundement May 2009: Power generation July 2009: slope deformation started Scale of the unstable slope: Height: 700m; Width: 1000m; Volume: 70 M m3
  6. 6. 500m 700m 2452m 2254m 50°
  7. 7. Topography and Geology
  8. 8. Deformation on the head cliff
  9. 9. Deformation on the slope 1989 March 2010 May 2013
  10. 10. Slope deformation by remote sensing 1.interferometric synthetic aperture radar (INSAR) ALOS PALSAR image list 2. Optical imagery ALOS PRISM image list
  11. 11. Results from INSAR Analysis Before impoundment: Nov. 9, 2007-June 10, 2008 < error (10cm) After impoundment: 2009-12-14~2010-01-29 2009-12-31~2010-02-15 Coherence: low a: 2007-12-09~2008-01-24 b:2008-01-24~2008-03-10 c:2008-03-10~ 2008-06-10
  12. 12. Optical imagery analysis (ALOS PRISM)  Imageries at two differing periods were processed  In case of no/small deformation, change in the gray value of the processed image will be very small.  The area where deformation occurred will show blue or yellow color in different phases Before impoundment: 2007-11-14~2008-07-01 No change in gray value No deformation > 2.5 m
  13. 13. Optical imagery analysis (ALOS PRISM) After Impoundment: 2008-07-01(before) ~2009-04-03(after) No change in gray value No/small deformation
  14. 14. Deformation after impoundment 2009-04-03 ~ 2010-05-22 Most part of the slope are in gray color Max displacement: 3 pixels, 3×2.5m=7.5m
  15. 15. View from Google Earth
  16. 16. Summary InSAR data: Deformation before the impoundment was very small. ALOS PRISM: No obvious deformation during the period from November 2007 to April 2009. Deformation with the horizontal displacement up to 7.5 m occurred during the period from April 2009 to May 2010. The response of sliding to the increasing water lever suggests that the sliding surface may be locating near the river bed. The cracks occurring on the terrace crest of the slope and the continuing deformation reveals that the slope may not be sliding as a whole.
  17. 17. What is happening now?
  18. 18. Landsliding monitoring
  19. 19. Landsliding monitoring
  20. 20. Countermeasures now Surficial displacement monitoring system: GPS + standard survey
  21. 21. 290m 750 m
  22. 22. Deforming on the upper surface
  23. 23. Countermeasures now Inside the deforming mass Survey tunnel + Vertical boring and monitoring
  24. 24. Sliding surface inside the tunnel
  25. 25. What is happening now?
  26. 26. What we are doing now Seismometers
  27. 27. What we are doing now Shear behavior of the sliding surface Samples
  28. 28. Thanks

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