Identifying Partly Earthen and Partly Rockfill Dams

Dams are constructed using various materials and methods, depending on the geography, availability of materials, and the purpose of the dam. Different types of dams include concrete gravity dams, arch dams, buttress dams, earthen dams, and rockfill dams.

An earthen dam is primarily constructed from compacted soil, while a rockfill dam is built using compacted rock, often with an impermeable zone like clay or concrete on the upstream side or in the core. Some dams combine these materials, being partly earthen and partly rockfill, often referred to as earth and rock-fill dams or embankment dams.

Analyzing the Given Dam Options

Let's look at the construction type of each dam provided in the options:

• Tehri Dam: Located in Uttarakhand, India, the Tehri Dam is a multi-purpose rock and earth-fill embankment dam. This means it is constructed using a combination of compacted earth and rock materials, fitting the description of being partly earthen and partly rockfill.
• Bhakra Dam: Located on the Sutlej River in Himachal Pradesh, India, the Bhakra Dam is a concrete gravity dam. It is constructed primarily using concrete and relies on its weight to resist water pressure.
• Koyna Dam: Situated in Maharashtra, India, the Koyna Dam is also a concrete gravity dam. Similar to the Bhakra Dam, its stability comes from its massive concrete structure.
• Sardar Sarovar Dam: Located on the Narmada River in Gujarat, India, the Sardar Sarovar Dam is another example of a concrete gravity dam.

Conclusion

Based on the construction types of the given dams, the Tehri Dam is an earth and rock-fill embankment dam. This classification means it is built using both earth and rock materials, making it partly earthen and partly rockfill.

Therefore, among the given options, the Tehri Dam is the one that is partly earthen and partly rockfill.