1. Large Scale Embankment Failure
IMPACT
WP2.1
Breach Formation -
Large Scale Embankment Failure
Kjetil Arne Vaskinn Statkraft Grøner AS
Forskjellige firma sendte inn hvert sitt prosjektforslag man disse hadde så mye til felles at det ble bestemt å slå disse sammen til et stort prosjekt som inkluderer store deler av bransjen.
HMK-02

2. Norwegian national project:
IMPACT
Norwegian national project:
Stability and Breaching of
Rockfill dams
Forskjellige firma sendte inn hvert sitt prosjektforslag man disse hadde så mye til felles at det ble bestemt å slå disse sammen til et stort prosjekt som inkluderer store deler av bransjen.
HMK-02

3. Large Scale Embankment Failure
WP2.1 Breach Formation -
Large Scale Embankment Failure
The objective of this work package
is to undertake controlled failure of large
scale embankments in order to monitor
and record the failure process and
mechanisms in detail.
This will provide valuable data to assist in
understanding the fundamental failure
process, for developing predictive
models and for assessing the validity
of smaller scale laboratory testing.

4. Deliverables

5. Milestones and Expected Results

6. Large-scale field test
Lysaker/Oslo
Tromsø
Trondheim
Large scale test-site
Arctic circle

7. Large-scale field test
Damsite

8. Large Scale Field Test

9. Large Scale Field Test
Test-site

10. Large Scale Field Test

11. Test of drainage capacity
of the dam toe 2001
Dam-toe

12. Large Scale Field Test 2001

13. Large Scale Field Test 2001

14. Large Scale Field Test 2001

15. Large Scale Field Test 2001

16. Large Scale Field Test 2001

17. Large Scale Field Test 2001

18. Large Scale Field Test 2001

19. Large Scale Field Test 2001

20. Large Scale Field Test 2001

21. Field tests 1:2002
Homogeneous (maximum cohesive) dam of silty clay (25% clay, >65% silt, <10% sand )
Failure by overtopping
Optimal water content ~ 15%, 0.15 m layers, compaction by dozer
2 layers of pore pressure gauges
2 m
2,0 1
H = 6 m

22. Field tests 2a:2002
Homogeneous (minimum cohesive) dam. Gravel 0-60 mm, fines (0,074mm)<5%, 4 mm<d50<10 mm, dmax<60 mm
Optional slope protection test with rockfill (0-500mm).
Failure by overtopping – no protective layer.
0.5 m layers, compaction by 4 ton vibrator roller, 2 layer with pore-pressure sensors
2 m
0,9 m
1,7 1
H=5m

23. Field tests 2b:2002
Homogeneous (minimum cohesive) dam. Gravel 0-60 mm, fines (0,074mm)<5%, 4 mm<d50<10 mm, dmax<60 mm
Failure by overtopping – no protective layer.
0.5 m layers, compaction by 4 ton vibrator roller, 2 layer with pore-pressure sensors
2 m
1,7 1
H=5m

24. Field tests 3:2002 B A Composite rockfill dam. Failure by overtopping.
Central moraine core (Fines (0,074 mm)>25%; dmax < 60 mm)
Rockfill support: A mm, d10 > 10 mm in downstream fill
B mm in upstream fill
1 m layer, 4 ton vibrator roller. 2 layer with 2 pore-pressure sensors in the core, 3 sensors at the foundation in the supporting fill.
B = 2,5m
B = 1m 1
1,5
H=6m
H=5,5m 1 B A 4

25. Field tests 4:2002 Toe stability. Rockfill support 300-400 mm
Construction: 2- 3 layers (2 m)
Instrument: 6 pore-pressure sensors at the foundation
2 m
1,5 1
H = 4-6m

26. THE PLAN FOR THE FIELD TEST
OUTLINE
1. Preparing the site for the test dam
Building of transport road to the riverbed.
Prepare the foundation of the test-dams.
Preparing the side-slopes
2. Selection and transport of the of the materials
for dam-building.
3. Building of test-dam #1
4. Test #1
5. Cleaning up at dam-site and preparing for test #2.
Step 2-5 will be repeated for each test.

27. Data Requirements Breach formation geometry Water levels
Discharge into the reservoir upstream of the test-dam
Flow/velocity
Sediment movement
Material properties

28. Breach formation geometry
3D surface of breach at any time
Photo, Video, Photogrammerty
Sonar upstream
Some points within the body either through
wires or 'balls'.

29. Breach formation geometry From the Chinese- Finnish research work

30. Breach formation geometry From the Chinese- Finnish research work

31. Breach formation geometry Photo/video
Paint a grid across whole of embankment - including crest and
upstream face to aid video and photography
Video to be taken from: Downstream: 3 camera stations (2001-2)
Above: 1 camera (?)
Upstream: 1 camera
Still camera shots Downstream 3 camera or from video
footage
Quality is high enough.(Morten Strand F&W)
Aerial video/photo will require some form of structure to support
camera
Photogrammetry offers a possible method for identifying movement of embankment material. Requires at least two cameras, firing simultaneously, at a fixed spacing.

32. Photopoints

33. Wires

34. Movement sensors Use of movement sensors - floating balls etc.
A possible solution is to bury sensors within the
dam that are released as erosion occurs.
These sensors need to be uniquely identifiable,
unrestricted by cables, traceable or disposable.

35. ”Dambreak” Sensor
Sensor contains tilt switch which will trigger when the sensor moves.
A number of sensors will be built into the dam. The number of sensors will determine the resolution. Need to position all sensors by survey.
Processor with built-in timer will log and store time for movement.
Stored data together with the sensor ID will be downloaded to a PC after collecting the sensors downstream.
Sensor will be housed in watertight (IP68) enclosure.
Floating element will ease location of the sensors after the dambreak.
Sensor size approx. 10x10x10 cm.
(To be followed up)

36. Sonar Offers a possible means of monitoring breach growth underwater.
Not appropriate for downstream conditions,
but will be placed underwater upstream to show
growth of breach through upstream face.

37. Sonar - Example

38. Water levels in the river and reservoir
Water level - automatic recording (pressure sensors)
upstream of the test-dam (2)
downstream (several along the river to monitor the flood wave)

39. Pressure sensors in the dam

40. Inflow Rate to the test-reservoir
Discharge through the gates at Røssvassdammen = inflow to the reservoir upstream of the testdam
Gate opening every minute
Water level in the reservoir

41. Discharges Stage/waterlevel:
Discharge from calibrated stage-discharge relationship
automatic sampling of water pressure/water level + manual readings

42. Discharges from water velocity
Water-velocity recordings - automatic recording by use of ADCP:
1) Floating on the surface
2) Mounted at the bottom

43. Discharge/leakage through the test-dam
(before failure)
1. Direct measurement
Gauge readings
ADCP (EasyQ )
2. Indirect by simulation/calculation

44. EasyQ velocity data

45. Discharge during the faillure
1. Direct measurement
ADCP (Aquadopp Profiler - bottom mounted)
Gauge readings
Problem with gauges downstream due to sediment/debris flow.
2. Indirect by simulation/calculation

46. Aquadopp Profiler

47. Sediment movement
By survey / calculation of bed surface changes

48. Sediment movement
By survey / calculation of bed surface changes

49. Material properties Particle size distribution Liquid / plastic limit
Type of clay
Compaction
Rock properties (interlocking effect)
Clay will require further tests – chemistry
Should we be undertaking pre and post
failure tests on samples?