Session 3 - Case histories KARIBA DAM

Transcription

1 ICOLD COMMITTEE ON CONCRETE DAMS SPANISH COMMITTEE ON CONCRETE FOR DAMS INTERNATIONAL JOURNAL ON HYDROPOWER & DAMS WORKSHOP October 18 & 19, 2007 Granada, Spain CHEMICAL EXPANSION OF CONCRETE IN DAMS & HYDRO-ELECTRIC PROJECTS Session 3 - Case histories KARIBA DAM by Bernard GOGUEL and Kozanai GURUKUMBA bernard.goguel@coyne-et-bellier.fr kgurukumba@yahoo.co.uk

2 Kariba ZIMBABWE ZIMBABWE

3 KARIBA DAM : H 128 m L 617 m C SOUTH C 181 km 3, of which 116 /Min Op. Lev. ICOLD Durban 1994 Q 68 R 86 Int. WP&DC Jan 1996 NORTH

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5 million m 3 concrete All existing tests in for checking the cement aggregate compatibility were done, without detecting any sign of expansion risk

6 30 years 10 years Construction 1963 Impounding complete 1983 Dam behaviour study => additional instrumentation Int. WP&DC (June) 1992 FREDERICTON CEA-CANCOLD Conference 1994 ICOLD Durban Q.68-R Int. WP&DC (Jan.) 1997 ICOLD Florence Q years 2007 GRANADA workshop

7 Monitoring show moderate concrete expansion: /year * * vertically, far from the spillway 1989: AAR typical gel was detected by LCPC (on 1 sample) 1994: drilling works 6 bays=> gated more submerged laboratory spillway analyses which confirmed

8 Min Op. Lev. + 0,50 m

9 Relatively small reservoir level operating range, compared to the dam high Nevertheless => significant upper arch stresses variations

10 KARIBA : gravity thrust block... and underground buttresses Zambezi River after dam concreting completion (C 1959)

11 50 m KARIBA South Abutment (Upper Right Bank) Gravity thrust block and underground buttresses across quartzites and weathered gneiss, down to the sound deep gneiss : m 3 concrete before end of impounding in 1963 Réf. Proc. Inst. Civ. Engr / 1962 and, with associated monitoring : CIGB 1991 (Q.66 R.14) & 1994 (Q.68 R.86)

12 Kariba South Bank General layout plan view: (1) Power station intakes (2) Tailrace tunnels (3) PHAT portal (4) Underground buttresses (and SCAT Surge Chamber Access Tunnel below) DA Drainage Adit EA Exploratory Adit Q Quartzite mass with mica seams FQ Fresh Quartzite WGn Weathered Gneiss Gn Sound Gneiss A Ref. Q.68 R. 86 (ICOLD 1994)

13 South Abutment, seen from downstream: Section A - A (2) = tailrace tunnels (4) = Thrust Block and Buttresses Q Quartzite mass with mica seams WGn Weathered Gneiss Gn Sound Gneiss P8 SCAT Surge Chambers Access Tunnel EA Exploratory Adit: old adit, parallel to the Power House Access Tunnel PHAT. Note: both are orientated at 45 to this cross section. P9 = pendulum n 9, in P1 shaft P8 bank side, down to PHAT P13 not shown (at thrust block toe) Additional instrumentation (1) = pendulums in Dam Wall & South Bank Ref. Q.68 R. 86 (ICOLD 1994)

14 COYNE vibrating wire strainmeters : extensometers embedded in the concrete Kariba : 263 nos. ( ), 207 i.e. 79 % in 2007

15 Average : Fredericton 1992

16 Strainmeters Group 0.4 Upstream (central block, mid height) RWL C /year UC /year U2 0.4U3 0.4U U /year RWL / Granada 2007

17 Precise levelling : crest rise Geodetic : mm? upstreamwards crest deflection Fredericton 1992

18 RWL KARIBA CREST RISE (mm) 1.2 mm/yr mm/yr

19 Additional instrumentation (1) 14 pendulums (direct and inverted), 25 reading points (Huggenberger) 2 borehole extensometers (6 m) New geodetic : few points on the crest, no more targets on the d/s face, improved reference pillars, traverses (polygonals) in 2 galleries

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21 Downstream (mm) 50 mm (+ downstream) T434 data (and geodetic meas. dates) Pendulums Target T434 Lake Level Geodetic m Upstream janv-1960 janv-1965 janv-1970 janv-1975 janv-1980 janv-1985 janv-1990 janv-1995 janv-2000 janv years Calculs

22 MODAP KARIBA MODAP : MODel Accompanying the Projet

23 Reservoir level influence on concrete swelling rate : modelisation in the case of Kariba ICOLD Florence 1997, Q74-9 Calculs BETHY

24 Thrust / South Abutment over years model Identified possible adverse effects

25 Identified possible adverse effects Additional (3) instrumentation & monitoring Plumblines Borehole extensometers Piezometers

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28 Maxi storage 181 km 3 Max June km 2 = 5 km 3 /m 13 m Dead storage 116 km 3 Sealing plane 20 m 6 caterpillar gates 9.14 m Stopbeams (one set) 6 x 1500 m 3 /s

29 Upstream stopbeam rollerpath upper section (in the dry) Construction joint open due to concrete vertical expansion

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31 Upstream stopbeam U/S BIP joint Expanding concrete

32 Gate Smooth concrete, supporting the gate front seal Plane is deforming => Gate scrapping

33 1992 : gate scraping => smooth concrete surveys & restoration Ref. Water Power & D C Jan additional instrumentation 2 (borehole extensometers) => local expansion rates measured as 33 x 10-6 /yr

34 B A A B B A Front seal Gate B B Smooth concrete deflection

35 Additional Instrumentation (2): Borehole extensometers in the spillway section and some other locations in dam wall

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37 30 x 10-6 /yr (min 23, max 47) 13 & 38 (middle) 33 x 10-6 /yr 16 x 10-6 /yr 7 & 15 (17 /end pier) 20 (average)

38 Mid height leaks : downstream BIP s cracking on a construction welding level => specific maintenance works

39 Gate anchoring Roller tracks

40 1959

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42 30 years 20 years Construction 1963 Impounding complete 1983 Dam behaviour study 1987 Additional monitoring (1: pendulums & geodetic) 1992 Int. WP&DC (June) / maintenance & monitoring 1992 FREDERICTON CEA-CANCOLD Conference 1994 ICOLD Durban Q.68-R.86 / addit. monit. (2) 1996 Int. WP&DC / gate sealing plane restoration 1997 ICOLD Florence Q.74-9 / modern calculations 2005 Additional monitoring (3 = South Abutment) 2007 GRANADA workshop / intrusive examinations

43 Concrete expansion = long term process of understanding, monitoring, modelling + special surveillance & maintenance works

44 Concrete expansion = long term process of understanding, monitoring, modelling Chemistry explanation not developed here Rheology: calculation model / observations help appraisal of adverse effects (dam stability) for optimizing remedial measures

45 Concrete expansion = long term process of understanding, monitoring, modelling Chemistry explanation not developed here Rheology: calculation model / observations help appraisal of adverse effects (dam stability) Mechanical (spillway gate reliability): smooth sealing plane restoration, load gauges and hoist load monitoring, stopbeam and gate grooves surveys, gate anchors intrusive examination (++)

46 Survey and maintenance works needs close joint studies on M&E and Civil Works Examplary working relationship developed for years between GIBB (now JACOBS) and COYNE ET BELLIER experts, acting jointly for Zambezi River Authority To be encouraged elsewhere!!

47 Thanks for your attention