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RCC dams, due to construction procedures and materials, possibility
of water infiltration from the reservoir is higher than in conventional
concrete dams. The main causes are horizontal lift joints, contact
between the RCC and the conventional concrete, higher permeability
of the concrete mix, induced or random vertical joints. Solutions
can be either more accurate concrete mix design and construction procedures
(this reducing to some extent the advantages of RCC), or the construction
of a low permeability upstream facing.
In the construction
of new Roller Compacted Concrete (RCC) dams, the geomembrane provides
the watertight element, while the concrete provides the static function.
Geomembranes have been successfully used as watertight element in
many RCC dams worldwide. Two different patented systems are available.
The Winchester system, by embedding the geomembrane in prefabricated
concrete panels constituting the upstream face, protects it from
the environment. The Sibelon system leaves the drained geomembrane
exposed, allowing dehydration of any seepage water and easy control
and maintenance of the waterproofing liner.
The installation
of a synthetic geomembrane as the waterproofing element on the upstream
face provides the following benefits:
- stops water
infiltration, bridging lift joints and connections with conventional
concrete elements
- reduces/prevents
the formation of uplift pressures
- can withstand
seismic events, bridging potential opening of cracks and fissures
- provides freeze/thaw
protection to the upstream face
- can be quickly
installed, reducing construction times and costs
- has a well documented
long durability
- allows use of
aggregates and cement of less stringent properties
- makes the entire
construction procedure more easy and therefore reliable.
In dams constructed
with these systems, rates of leakage through the facing have been
reported as virtually equal to zero.
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