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
Kariba ZIMBABWE ZIMBABWE
KARIBA DAM : H 128 m L 617 m C 1957-59 SOUTH C 181 km 3, of which 116 /Min Op. Lev. ICOLD Durban 1994 Q 68 R 86 Int. WP&DC Jan 1996 NORTH
07-1958 11-1958
07-1959 1 million m 3 concrete All existing tests in 1955-57 for checking the cement aggregate compatibility were done, without detecting any sign of expansion risk
30 years 10 years 1958-59 Construction 1963 Impounding complete 1983 Dam behaviour study => additional instrumentation 1987 1992 Int. WP&DC (June) 1992 FREDERICTON CEA-CANCOLD Conference 1994 ICOLD Durban Q.68-R.86 1996 Int. WP&DC (Jan.) 1997 ICOLD Florence Q.74-9 10 years 2007 GRANADA workshop
Monitoring show moderate concrete expansion: 11.10-6 /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
Min Op. Lev. + 0,50 m
Relatively small reservoir level operating range, compared to the dam high Nevertheless => significant upper arch stresses variations
KARIBA : gravity thrust block... and underground buttresses 1961-62 62 Zambezi River after dam concreting completion (C 1959)
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 : 65 000 m 3 concrete 1961-62 before end of impounding in 1963 Réf. Proc. Inst. Civ. Engr. 1960 / 1962 and, with associated monitoring : CIGB 1991 (Q.66 R.14) & 1994 (Q.68 R.86)
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)
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)
COYNE vibrating wire strainmeters : extensometers embedded in the concrete Kariba : 263 nos. (1958-59), 207 i.e. 79 % in 2007
Average : +23 +11 + 5-2 Fredericton 1992
800 10-6 Strainmeters Group 0.4 Upstream (central block, mid height) RWL 490 600 480 400 2 3 1 4 C 16. 10-6 /year 470 0.4UC 200 8. 10-6 /year 460 0.4U2 0.4U3 0.4U4 0 450 0.4 U1-5. 10-6 /year RWL -200 1959 1969 1979 1989 1999 08/2007 440 Granada 2007
Precise levelling : crest rise Geodetic : + 10-20 mm? upstreamwards crest deflection Fredericton 1992
100 490 RWL 90 485 80 480 3-5 70 60 KARIBA CREST RISE (mm) 1.2 mm/yr 475 470 0-2 50 465 6-8 40 2.3 mm/yr 460 9-11 30 455 38-40 20 450 33-35 10 445 0 1960 1965 1970 1975 1980 1985 1990 1995 2000 2005 440
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
Downstream (mm) 50 mm (+ downstream) T434 data (and geodetic meas. dates) 490 40 485 30 480 20 475 10 Pendulums 470 0 465-10 -20-30 Target T434 Lake Level Geodetic m. 460 455 450-40 Upstream 445-50 janv-1960 janv-1965 janv-1970 janv-1975 janv-1980 janv-1985 janv-1990 janv-1995 janv-2000 janv-2005 440 32 years Calculs 1996-97
MODAP KARIBA 1996-1997 MODAP : MODel Accompanying the Projet
Reservoir level influence on concrete swelling rate : modelisation in the case of Kariba ICOLD Florence 1997, Q74-9 Calculs BETHY 1996-97
Thrust / South Abutment over 32 + 20 years model 2015 1995 1963 Identified possible adverse effects
Identified possible adverse effects Additional (3) instrumentation & monitoring Plumblines Borehole extensometers Piezometers
Maxi storage 181 km 3 Max June 488.50 5 000 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
Upstream stopbeam rollerpath upper section (in the dry) Construction joint open due to concrete vertical expansion
Upstream stopbeam U/S BIP joint Expanding concrete
Gate Smooth concrete, supporting the gate front seal Plane is deforming => Gate scrapping
1992 : gate scraping => smooth concrete surveys & restoration Ref. Water Power & D C Jan 1996 + additional instrumentation 2 (borehole extensometers) => local expansion rates measured as 33 x 10-6 /yr
B A A B B A Front seal Gate B B Smooth concrete deflection
Additional Instrumentation (2): Borehole extensometers in the spillway section and some other locations in dam wall
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)
Mid height leaks : downstream BIP s cracking on a construction welding level => specific maintenance works
Gate anchoring Roller tracks
1959
2007 ++
30 years 20 years 1958-59 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
Concrete expansion = long term process of understanding, monitoring, modelling + special surveillance & maintenance works
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
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 (++)
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!!
Thanks for your attention