Fundamentals of temperature measurements in dams
Tair (t) Seasonal temperature variation T(t,z)
Experiences from seepage monitoring using optical fibres
T (t)
Geothermal flow
Dr. Sam Johansson HydroResearch
[email protected] www.hydroresearch.se
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Dr. Mahmoud Farahdiroushan, Dr. Tom Parker, and Dr. Dan Watley Sensornet Ltd, London www.sensornet.co.uk Sep 11-12, 2006 Stockholm
vT
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European Working Group on INTERNAL EROSION IN EMBANKMENT DAMS
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Seasonal temperature variation in the water creates seasonal temperature variation inside the dam. Increasing seepage causes increased annual temperature variation, and shorter time lag. The temperature inside the dam is mainly determined by seepage.
Sep 11-12, 2006 Stockholm
Presentation and evaluation methods
European Working Group on INTERNAL EROSION IN EMBANKMENT DAMS
DamTemp – Evaluation of concentrated seepage
– Subjective/qualitative evaluation – DamTemp (concentrated seepage – i.e. Internal Erosion) – FEM (such as SUTRA, SEEP/W+SEEP/T, FEFLOW) 18 16
12
o
Temperature ( C)
14
10 8 6 4 035:1
2
045:1 060:1
0 Jan 2001
Jul 2001
Jan 2002
Sep 11-12, 2006 Stockholm
Jul 2002
Jan 2003
Jul 2003
Jan 2004
Jul 2004
Vibrating wire temperature sensors
Jan 2005
European Working Group on INTERNAL EROSION IN EMBANKMENT DAMS
Sep 11-12, 2006 Stockholm
European Working Group on INTERNAL EROSION IN EMBANKMENT DAMS
Temperature at single points with time
Temperature at single points with time
12.0
20 18 8.0
16 6.0
14 4.0
Temperature ( C)
+482.9 m +480.9 m +479.9 m
2.0
o
Temperature (oC)
10.0
Date
Temperature (oC)
0.0 12.0 2003-11- 2004-05- 2004-10- 2005-05- 2005-10- 2006-05- 2006-1001 01 31 01 31 02 31
12 10 8
10.0
6
8.0
4
6.0
2
4.0
0 97-01-01
+482.0 m +480.0 m +479.0 m
2.0
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Date
European Working Group on INTERNAL EROSION IN EMBANKMENT DAMS
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99-01-01
00-01-01
01-01-01
02-01-01
03-01-01
04-01-01
05-01-01
Date (YY-MM-DD) Q= 8.0E-06 m³/(s·m), H=0,5 m V08 +59.2 m Q= 1.8E-05 m³/(s·m), H=0,5 m V08 +60.7 m Q= 5.0E-04 m³/(s·m), H=0,5 m
0.0 2003-11- 2004-05- 2004-10- 2005-05- 2005-10- 2006-05- 2006-1001 01 31 01 31 02 31
Sep 11-12, 2006 Stockholm
98-01-01
Sep 11-12, 2006 Stockholm
Increased temperature variation Shorter time lag European Working Group on INTERNAL EROSION IN EMBANKMENT DAMS
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Hylte - Leakage test
Hylte - Leakage test Hose Siphon
0.8 Infiltration of 0.07 l/s
Temperature trend ( C/day)
GWL before and after the test
Daily trend 3 days before the test
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Embankment dam
0.4
Cable 0.8m below ground surface
0.0
Daily trend after the test -0.4
-0.8 1920
1910
1900
Cable Marking (m)
Result from leakage test, show the possibility to detect small local (some meters) seepage changes in the order of centilitres/s and metre. Sep 11-12, 2006 Stockholm
European Working Group on INTERNAL EROSION IN EMBANKMENT DAMS
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Sep 11-12, 2006 Stockholm
European Working Group on INTERNAL EROSION IN EMBANKMENT DAMS
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Application and installation principles
Installations in Sweden 1998-2006
• Seepage evaluation based on natural seasonal temperature variation
●7■ ●12■●20●3■ 18●■19 2 ■ ● 15
– Fibre installed deep inside the dam at repair/construction (Lövön and Aitik) – Fibre installed inside the downstream part when a toe berm is constructed (about 20 dams and dykes in Sweden) – Fibre installed in a downstream trench (Hylte and at a dam in France) – In standpipes at dams with high downstream water level (Bergeforsen)
●8 4 ■ 14●● 9 17● 10●●5 1●
■16 ● 13
● 11
●6
Sep 11-12, 2006 Stockholm
European Working Group on INTERNAL EROSION IN EMBANKMENT DAMS
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1. Lövön (1998) Seepage 2. Sädva (1999) Movements (Temperature) 3. Aitik, 2 dams (2000, 2005) Seepage and Movements 4. Ajaure (2001) Movements 5. Vargfors (2001) Seepage 6. Hylte dam and dyke (2002) Seepage 7. Suorva, West Dam (2003) Seepage and (2005) Movements, East Dam (2004) Movements 8. Bastusel, 4 dams (2004) Seepage 9. Gallejaure, 2 dams (2004) Seepage 10. Sandfors, 2 dams (2005) Seepage 11. Vässinkoski (2005) Seepage 12. Seitevaare (2005) Seepage and Movements 13. Bergeforsen (2005) Seepage 14. Grytfors, 2 dams (2005, 2006) Seepage and Movements 15. Porsi (2005) Seepage 16. Hällby (2005) Movements (Temperature) 17. Stensele (2006) Seepage 18. Parki (2006) Seepage and Movements 19. Randi (2006) Seepage and Movements 20. Porjus (2006) Seepage 21. Näs (2006) Seepage 22. Fläsjön (2006) Seepage
Sep 11-12, 2006 Stockholm
● Seepage ■ Movements
European Working Group on INTERNAL EROSION IN EMBANKMENT DAMS
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Temperature profiles in two standpipes with time
Bergeforsen – measurements in standpipes
An automated DTS system was taken into operation in September 2005.
17 new standpipes cc 10m + 6 old standpipes (up to 70m deep).
Sep 11-12, 2006 Stockholm
TB5 and T6 Oct 2003 – Aug 2006 Time step 3 days. European Working Group on INTERNAL EROSION IN EMBANKMENT DAMS
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Sep 11-12, 2006 Stockholm
European Working Group on INTERNAL EROSION IN EMBANKMENT DAMS
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Seitevaare Dam
Temperature profiles and difference Bergeforsen T6
0.50
Temperature (oC)
7.0
0.45
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106m high
0.40
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1700m long
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Cable in the toe for seepage measurements
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Cables on the crest for strain measurements
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Owned by Vattenfall Vattenkraft
0.35 6.5
0.30 0.25 0.20
6.0
0.15
Temperature diff (oC/d)
7.5
0.10
5.5
0.05 5.0 580
590
2005-10-03 14:30 2006-07-06 21:59
600
Length (m)
610
2006-01-04 19:06 Temperature difference (oC)
620
0.00 630
2006-04-04 20:19
Seepage flow rate less than 5 ml/(m,s). (or less than 10-6 m/s) Sep 11-12, 2006 Stockholm
European Working Group on INTERNAL EROSION IN EMBANKMENT DAMS
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Sep 11-12, 2006 Stockholm
European Working Group on INTERNAL EROSION IN EMBANKMENT DAMS
Seepage evaluation
14
Suorva
14
Measured Sept 23 Measured May 10
12
Q= 2.9E-05 (m3/s,m) H= 15 (m) Q= 2.5E-05 (m3/s,m) H= 15 (m)
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Temperature (oC)
10
Seepage flow (weirs) 30-65 l/s Calculated seepage flow 40-70 l/s
Q= 2.4E-05 (m3/s,m) H= 15 (m)
8 6 4 2 0 -2
Relative accuracy with high spatial resolution is much more important than absolute accuracy. Sep 11-12, 2006 Stockholm
European Working Group on INTERNAL EROSION IN EMBANKMENT DAMS
-4 0
20
40
60
80
100
120
140
160
180
200
Length (m)
15
Sep 11-12, 2006 Stockholm
European Working Group on INTERNAL EROSION IN EMBANKMENT DAMS
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Conclusions
Seepage measurement at Vässinkoski The Vässinkoski embankment dam was built in the 1960’s and is owned by Fortum Energy. The dam is 1300m long and 25m high.
Optic cable
Drainage pipes
The main purpose of this installation is to be a complement to the conventional seepage monitoring system. Sep 11-12, 2006 Stockholm
European Working Group on INTERNAL EROSION IN EMBANKMENT DAMS
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Evaluation based on natural temperature variation allows both detection and quantification of the seepage.
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Seepage/leakage measurements using optical fibres are sensitive (in the order of
