C.J. Pretorius¹, W.F. Schmidt¹ C.S. van Staden¹ K. Egger² ¹ Department of Water Affairs and Forestry, Republic of South Africa ² Schneider Ingenieur AG, Chur, Switzerland 10th INTERNATIONAL SYMPOSIUM ON DEFORMATION MEASUREMENTS Orange, California, USA THE EXTENSIVE GEODETIC SYSTEM USED FOR THE MONITORING OF A 185 METRE HIGH ARCH DAM IN SOUTHERN AFRICA
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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
• 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;
• 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