Embankment dam

the material of this PPt according to the RTU syllabus

1. Presented by Brijlata Sharma AP,civil department JECRC,Jaipur

2. What is? Embankment dams are water impounding structures . These are flexible structures which can deform slightly to conform to the deflection of the foundation . Embankment dam is primarily made out of earth and rock fragments . Thus, the term embankment encompasses both earth and rock-fill dams.

3. Types of Embankment Dam. 1. Rolled Fill Dam. 2. Hydraulic Fill Dam. The placed earth-fill type is widely used. three types, viz., diaphragm, homogeneous, and zoned.

4. Components of Embankment Dam.

5. Foundation . The foundation of a dam is the sole supporting medium resisting the vertical and horizontal forces. 2. Casing. As pointed out earlier, the shell imparts stability and protects the core . 3. Core. The core acts as an impermeable barrier and prevents the free seepage of water through the body of the dam . The minimum top width of the core should be 3 meters, and the final thickness has to be decided based on the practical considerations given below  ( i )  availability of suitable impervious material; (ii)  resistance to piping; (iii)  permissible seepage through the dam; (iv)  availability of other materials for casing, filter, etc.

6. Embankment Dam failures, Hydraulic Failures : i . Overtopping of the dam height. ii. Wave action towards u/s side of the dam. iii. Toe erosion. iv. Gullying . 2 . Seepage Type Failures: i . Piping; and ii. Sloughing.

7. The dam is overtopped when the volume of incoming flow into the reservoir is more than the actual storage capacity of the reservoir, or the capacity of spillway is not sufficient. Sometimes, the faulty operation of spillway also leads to the overtopping problem. Similarly, insufficient free board or settle­ment of foundation as well as embankment also cause the overtopping problem in earthen dam. Overtopping of the dam height

8. Wave Erosion : Wave action removes the soil particles from the unprotected part of upstream face of the dam, continuously. This is one of the effective factors to cause the hydraulic type failure in earthen dam.

9. Toe Erosion: Toe erosion in the earth fill dam, mainly occurs due to following reasons: ( i ) Erosion caused by the tail water; and (ii)   Erosion due to cross-currents produced by the storage water, spillway bucket or from the outlet, create the problem of hydraulic failure. This type of failure can be overcome by providing a thick layer of stone riprap on the downstream face up to the height of tail water level.

10. Gully Erosion Development of gully in earthen dam is the result of heavy down pour. Such type of failures can be eliminated by providing a proper size of berm , turf or good drainage system towards down-stream side of the dam. BERM a flat strip of land, raised bank, or terrace bordering a river or canal

11. Piping: The continuous flow of seepage water through the body as well as foundation of the dam is the main reason of piping. It causes catastrophic failures in the earth fill dams.

12. THANK YOU ANY QUESTIONS