Page 40 - Water and DSİ

Basic HTML Version

39
CHAPTER III - HYDROELECTRIC ENERGY
3.5.3.3.
Roller Compacted Concrete (RCC) Dam
RCC is used both in dam embankments together with auxiliary structures and dam rehabilitations.
As per date, more than 250 dams have been constructed all over the world. RCC is composed of
43% high quality aggromerant (more than 120kg/m³), 13% low quality aggromerant, and 6% of
hardfill. Cross section of RCC gravity dams are much similar to that of concrete gravity dams. RCC
dam embankments are constructed by spreading lengthways thickness of 30 cm concrete mixture
layers (slump value is 0), then compacting by vibrating cylinders. Generally, cement ratio is lower
than 90 kg/m³ and flyash ration is between 50-90 kg/m³ (for example 60 kg/m³ cement, 80 kg/
m³ flyash). Coarse aggregate is used (diameter is 38 or 75 mm). Aggregate absolute volume into
the mixture is %50-%60.
Flyash has important function as it reduces hydration temperature of the mixture. Upstream face
of RCCs is generally designed vertical, if the foundation is not strong enough, it may be slanting.
Dam axis is generally planned as linear. Unlike the upstream face, the downstream face is generally
slanting. Downstream face is stepped and layer thickness is 0.30 m or in multiples of 0.30 m.
Generally 0.90 and 1.20 m step heights are preferred.
Like concrete gravity dams, RCC dams entails sound rock foundations. But, RCC dams can be
built on less sound foundations. A foundation not suitable for concrete gravity dam may but
suitable for rockfill dam may also bear RCC dam. The important factor is that deformation of RCC
embankment is to be compatible with that of the foundation. Tunnels are opened inside the
embankment of RCC in order to carry out injection boreholes foundation injection work and
drilling drainage wells. Like concrete gravity dams, structures such as spillways and bottom outlets
are built on the RCC dam embankments.
3.5.4. Composite Dams
Composite dams may be designed on a very wide river beds and composed of different dam types
such as rockfill, hardfill, RCC, or concrete.
ALTINKAYA DAM
Location: Samsun, Embankment Type:
Claycore Rockfill Dam,
h (form talweg)= 195 m
Purpose: Energy (Installed Capacity (700 MW),
Construction date: 1980-1988
View
Cross-section