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CHAPTER III - HYDROELECTRIC ENERGY
Impervious Core Embankment Dams
Clay Core Rockfill Dam
Clay Core Composite Fill Dam
3.5.1.1. Rockfill Dams
Rockfill dikes are used when broken rock is available nearby excavation. Rock material is obtained
from excavation executed in the dam site or from quarry nearby Around the clay core there is filter
and transition zones. Fine, middle sized, and coarse materials are placed starting from filter
material towards slopes. Upstream and downstream slopes of embankment do not need protection
such as pitching. If upstream rock fill zone settled on alluvium, horizontal filters is linked with
vertical filters so as not to prevent water coming from alluvium from entering rockfill. Depending
on the foundation conditions of slopes of upstream face may be 2.2-2.75/1 (horizontal/ vertical)
and slopes of downstream face may be 1,7-2,2/1 (horizontal/ vertical. Settlement of 1% of the
dam height may be considered on the incompressible foundations or settlement of %2-4 of the
dam height may be allowed depending on the favorable foundation conditions.
3.5.1.2. Composite Filled Dams
Impervious of the dam is ensured by clay core or slanted clay core in the middle. Both sides of the
clay core may be relatively fine material such as earth, gravel, river silt, and sand. Filters are formed
on the upstream and downstream faces of the clay core.
If upstream embankment is semi impervious, horizontal drains (filters) will be formed for
instantaneous water level reduction. Likewise, horizontal drains can be arranged inside the
downstream embankment. Pervious material is to be preferred in upstream embankment in order
that water can be quickly drained when reservoir is instantaneously emptied. Seepage water is
emptied into the downstream by means of vertical filters in slope faces of clay core and horizontal
filters in the fountain. Filters prevent any water leakage from clay core. Filters function as
transition zone between clay zone and embankment zone. Filters are also used in order that
seepage water form clay core do not drift clay material.