BSc (Eng) Civil Engineering Research Project by
TANYARADZWA USHAMBA
SITE OF STUDY
Roode Elsberg Dam is a cupola double curvature concrete arch dam which is situated on the Sanddriftkloof River about 9km west of the town of De Doorns and 30km from Worcester in the Western Cape Province. The dam is the lower of two storage dams constructed along the river. Lakenvallei dam is located upstream of the dam. The two dams supply water for irrigation to farmers downstream of the dams as well as to those adjacent in the Hex River valley. The dam is owned by the Department of Water Affairs and Forestry, which also designed and built the dam.
The dam was completed in the year 1968 with a wall height of 72m above the lowest foundation level and 67m above river bed level. The dam has a centrally located uncontrolled ogee spillway and a crest length of 274m. The dam has a gross capacity of 8.21 million cubic metres. The net storage of the dam is 7.19 million cubic metres.
The dam consists of three inspection galleries. The upper and lower galleries run from the right flank to the left flank whilst the foundation drainage gallery is located only on the right flank. The surrounding terrain of the dam site is mountainous. The local rock at the dam site is the Table Mountain Group and the dam is also positioned near the axis of a major anticlinal fold. Quartzitic sandstone beds of the Peninsula Formation are located at the dam foundation (Department of Water Affairs and Forestry, 2011).
Structural analysis of the dam
The dam is constructed using vertical cantilever blocks which are grouted and glued together. Static measurements of the Roode Elsberg dam have been carried out since 1984. Currently, the key static measurements that have been carried out on the dam are; dam wall displacement, differential movement between blocks and dam wall inclination. These have been measured using geodetic surveys, crack gauges and tilt gauges respectively.
The micrometres are used to measure 3-D and 1-D deformations in the dam and its foundations. The crack gauges as well as the tilt gauges are read every three months whilst the geodetic surveys are carried out at six month intervals. The displacements are measured in the x, y and z directions (Moyo & Oosthuizen, 2011).
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