Download - Katse dam monitoring
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C.J. Pretorius¹, W.F. Schmidt¹ C.S. van Staden¹ K. Egger²
¹ Department of Water Affairs and Forestry, Republic of South Africa² Schneider Ingenieur AG, Chur, Switzerland
10th INTERNATIONAL SYMPOSIUM ON DEFORMATION MEASUREMENTSOrange, California, USA
THE EXTENSIVE GEODETIC SYSTEM USED FOR THE MONITORING OF A 185 METRE HIGH ARCH DAM
IN SOUTHERN AFRICA
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• Provide Lesotho with hydro- electricity
Features:• double curvature arch dam • 185 m high above foundation• crest length of 710 meter• crest thickness 9 meter• base width 60 meters
• To supplement water to the Gauteng industrial area of the Republic of South Africa;
Main objectives:
Katse Dam
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Lesotho Highlands Water Project
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Reference : Meas 9101
Point P01Meas du dv dz
9211 .0 .4 .49612 .1 .1 -11.69709 -.2 .1 -13.39803 -.2 .2 -14.69807 .1 .0 -15.3
Point P02Meas du dv dz
9211 .0 .3 -.59612 -9.9 2.4 -8.79709 -11.8 5.0 -17.39803 -12.4 5.1 -18.19807 -11.9 5.4 -19.1
Point P08Meas du dv dz
9211 3.2 -.6 -1.79612 4.0 -.7 -11.19709 3.9 1.0 -13.69803 3.6 1.4 -14.29807 3.8 .1 -15.4
Deformations after impounding started 1996
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• Correlation between pendulums and the Geodetic triangulation may take place on the crest of the dam, galleries inside the dam wall and exits on the downstream face of the dam
Concept of the Geodetic Deformation Measurements
• Close correlation between Instrumentation and Geodetic measurements
Correlation between Instrumentation and the Geodetic System
• Results of instruments which record relative displacements, when evaluated together with Geodetic results, their relative displacements become absolute
• Multistage Geodetic system - full, reduced and mini measurements have to be employed
• Establishment of an extensive triangulation network
Measurement intervals
• Concrete dams are subject to expansion and contraction because of changes in temperature and pressure of the water load between summer and winter• Monitoring therefore takes place during late summer (February) and winter (August) when the expansion and contraction is at its maximum and minimum
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INTRODUCTION
Basic Layout:
• Instrumentation• Pendulums• Triangulation Network• Traverses & Pendulums
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43 Vibrating Wire Extensometers442 Vibrating wire Jointmeters 28 Vibrating wire Strain gauges 64 Thermometers100 Vibrating wire Piezometers 22 Vibrating wire pressure transducers 24 Clinometer 8 Trivec stations .... Leakage Weirs .... Water Level measuring Devices ext
INSTRUMENTATION
Consists of:
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Equipment Used
Leica TC2002 Leica TCA2003 Kern H.D. Tripod Kern Plummit
Kern E2 Iseth Distometer Leica NA3003 60 cm Digit Scale
Illuminated Target Altrimetric 60cm Digit Scale
Crest TargetsInstrument Adaptors
Vertical TargetIlluminated Targets
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TRIANGULATION NETWORK
5 Primary Pillars
7 Secondary Pillars
4 Crest Pillars6 Gal Exit Pillars4 Exit Brackets
6 Primary Benchmarks
22 Secondary Benchmarks
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TRAVERSES & PENDULUMS
17 Hanging Pendulums9 Inverted Pendulums
6 Optical Align Brackets6 Pendulums Anchors
2060
2005
1945
1900
Traverse Brackets
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Crest Pillar
2 Altrimetric wire anchors
The Arch Dam
19 Parapet targets
Gal Exit Pillars
6 Opt. A. Points
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Connections Traverse - Net
Pendulum Chamber
Gal Exit Pillar with pendulum chambers
Opt Alignment Point
Inverted Pendulum
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El : 2005D- GALLERY
7 Hanging Pendulums7 Pendulum Anchors
5 Gal Exit Points
38 Traverse Brackets
6 Pillars
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D - ACCESSEl:2008 - 2000
PillarsStation Points
Brackets
Exit
Exit
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Dam WallE Gallery
Left FlankRock Abutment
Gallery ExitPillar
Gallery ExitPoint
Traverse Pillars/Brackets
E - ACCESSEl: 1994 - 2036
Gallery ExitBracket
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Crest Benchmarks Traverse Brackets Altrimetric Wires
PRECISE LEVELLINGON DAM WALL
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Adjustment Method used
• Helmert/91 program system
• Three-dimensional adjustment
• Based on theory of least squares
Definition of Adjustment
• Constants and Unknown parameters (co-ordinates etc.)
• Definition of the generalised Helmert - transformation
• Definition of an adequate stochastic model
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Network
Mean Error Ellipses (U,V) Code A B Theta Mhe mm mm o mm Primary Pillar : P01 .39 .28 58.58 1.49 El 2060 Pillar : P115 .23 .19 85.13 .46 Alignment Point : R111 .40 .39 122.11 .50 Parapet Target : 111 .54 .52 37.04 .50 Bench mark : C11 ..... ..... ........ .47 El 2005 Pillar : P200 .27 .22 90.44 .43 El 1945 Pillar : P300 .28 .23 88.46 .42
The mean error ellipses depend on:
• Accuracy of observations• Geometry of the geodetic network, and• Selection of fixed points/Helmert control points
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Traverses
Mean Error Ellipses (U,V) Code A B Theta Mhe mm mm o mm El 2005 Right Flank : 253 .34 .29 160.15 .30 Centre Bracket : 200 .14 .09 179.06 .17 Left Flank : 236 .22 .16 38.04 .24El 1945 Right Flank : 337 .67 .22 150.49 .37 Centre Bracket : 300 .13 .10 179.42 .24 Left Flank : 336 .62 .21 28.16 .42El 1900 Right Flank : 427 1.93 .57 153.31 .67 Centre Bracket : 400 .70 .44 179.20 .59 Left Flank : 426 1.67 .52 27.55 .69
Optical Align Point El 2052 : TA11 .47 .42 73.47 .... Hanging Pendulum : DH0 .49 .39 101.09 .... Inverse Pendulum :VKM0 1.37 .59 177.18 ....Altrimetric Wire : AW11 .... .... .... .35
Mean error ellipses refer to Optical Alignment and Galleryexit points as fixed points in the adjustments
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Horizontal Displacements El. 2060
Winter
Summer
-16 mm
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Summer
Winter
- 5 mm
Horizontal Displacements El. 2005
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Summer
Winter- 4.3 mm
Vertical Displacements El. 2060
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0.2 mm
Vertical Displacements El. 2005
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Left- Right Flank Contour DisplacementEl. 2060, 2005, 1945 and 1900
Right Flank Left Flank-7.5 - -8.5 mm+7.5 - +8.5 mm
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Up/Downstream Contour DisplacementEl. 2060, 2005, 1945 and 1900
-20.0 - -17.5 mm -10.0 - -7.5 mm-10.0 - -7.5 mm
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Vertical Contour DisplacementEl. 2060, 2005, 1945 and 1900
-7.5 - -6.25 mm
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Mapeleng CrackUpstream 10 Km on right flank1.5 Km long , up to 70mm wide
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• The Geodetic Scheme is of a high standard
• The scheme gives a high degree of information on the behaviour of the dam
• Scheme is not only based on the network and traverse disposition but also on the inclusion of the total pendulum system
• Scheme offers a variety of reduced measurements
• Easily accessible and ensure a high efficiency
• Provides adequate geodetic information of the structure and the surrounding areas over a long period of time.
Conclusions
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