Correct Answer - Option 4 : Rockfill dam
A dam is a barrier that impounds water or underground streams. It generally serve the primary purpose of retaining water, while other structures such as floodgates or levees (also known as dikes) are used to manage or prevent water flow into specific land regions.
Classification of dams based on material of construction:
1. Rigid dam:
- It is constructed with a rigid material such as stone, masonry, concrete, steel, or timber.
- Steel dams (steel plates supported on inclined struts) and timber dams (wooden planks supported on a wooden framework) are constructed only for small heights (rarely).
2. Non-rigid dam (embankment dams):
- It is constructed with non-rigid material such as earth, tailings, rockfill, etc.
- Some of the Non-rigid dams are -
(a) Earthen dam:
- Constructed with the help of gravel, sand, silt, clay etc
- In some cases, part of the length of the dam is constructed as an earth dam and the rest (excluding the spillway) as a masonry dam. Such dams are called masonry cum earthen dams.
- Earthen dams are provided with a stone masonry or concrete overflow (spillway) section. Such dams are called composite dams.
(b) Tailings dam – Waste or refuse obtained from mines
(c) Rockfill dam – Rock material supporting a water-tight material on the u/s face
(d) Rockfill composite dam – Rockfill on the d/s side and earth fill on the u/s side