In the case of an Earth and Rock Fill Dam or a Concrete Faced Rock Fill Dam rock fill will represent the largest volume of material required to build the dam wall. Often the cheapest way to obtain this large volume of rock is simply to use the rock that must be excavated during the building of the spillway for the dam, provided the rock from the spillway is of good enough quality to be used to build the dam wall. This can be a particularly economic dam design if the spillway excavation is able to supply the entire amount of rock fill needed to build the dam.
||Pindari Dam, a Concrete Faced Rock Fill Dam with a spillway-cum-quarry ie the spillway excavation provided the entire amount of rock fill needed to build the dam. This photograph shows the original Pindari Dam, before enlargement.
Other construction materials which may be required for an embankment dam are clay (for the core of an earth and rock fill dam) and sand and gravel (for concrete aggregate and also for filter zones which are placed between the clay core and rock fill of an earth and rock fill dam. An important factor in the cost of construction materials is the distance they must be hauled from their source to the dam site. Where large volumes of material are required (eg rock fill) it is particularly important that a source be found close to the dam site.
Cement and concrete aggregate are, of course the main construction materials required for a concrete dam. Construction methods have evolved over the years as illustrated by the following examples:
- Burrinjuck Dam, completed in 1928. At this time it was common practice to embed large rocks and boulders (known as "plums") in the concrete during the concrete placement pours in order to save on the volume of cement used in the concrete.
- Warragamba Dam, completed in 1960 is a conventional straight concrete gravity dam. The dam was designed as a series of vertical blocks bounded by vertical, keyed joints, which allowed relative movement during construction. These joints were later grouted, when movement and shrinkage had taken place. The design strength for the bulk of the concrete was 28 MPa at 6 months.
A recent development is the Roller Compacted Concrete (RCC) dam where the concrete is compacted by a roller in a similar fashion to that used to compact rock fill construction materials eg Willow Creek Dam, USA.
Natural materials (clay, sand, gravel, rock fill) still form the bulk of the materials used to build many dams. However, man-made geosynthetic materials are increasingly being used in engineering construction for special purposes.
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