Home  About US  Clients  Dams  Canals  Tunnels Hydraulic  Tunnels Traffic  Reservoirs  Joints  Underwater  Civil Works  Materials mailing address: Corso San Gottardo 86 6830 Chiasso Switzerland ph. ++41 91 6954000 fax ++41 91 6954009 e-mail: info@carpitech.com www.carpitech.com DAMS Concrete Dams     RCC Dams     Embankment Dams     References CONCRETE DAMS Environmental, foundation or concrete chemistry conditions, such as AAR, lead to water infiltration in the dam body, with subsequent cracking, spalling and deterioration of concrete. Over time the infiltration increases: fines and calcite from the concrete are transported and may cause clogging of the drains; water saturates the dam body; undesirable uplift pressures increase and the factor of safety is reduced; productive water is lost and further deterioration is accelerated. The installation of a synthetic geomembrane on the upstream face, with a drainage system behind, provides the following benefits: stops water infiltration, bridges joints and even large cracks reduces/prevents the formation of uplift pressures provides freeze/thaw protection to the face promotes a substantial reduction in water content of the dam body (dehydration) may assist in retarding alkali-aggregate reaction (AAR) can withstand seismic events, bridging potential openings of cracks and fissures minimum surface preparation is required can be quickly installed, in the dry and underwater has a well documented long durability more than 20 years maintenance-free history. CARPI has lined more than 45 large dams of all types, to a maximum height of 174 m (571 ft). All installations, some of which are more than 25 years old, prove the system's excellent durability, even in the most severe environments, from the Alps to the Equator. Pracana, Portugal, 1992 Girotte, France, 1991 Illsee, Switzerland Alpen Gera, Italy, 1994 Kadamparai, India, 2005 Publino, Italy Beli Iskar, Bulgaria, 2004 RCC DAMS In 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. Miel I, Columbia, 2002 Burnett River, Australia, 2004 Mujib, Jodran, 2002 Olivenhain, USA, 2003 EMBANKMENT DAMS Earth and rockfill dams are usually designed with an impervious core consisting of fine graded soils. When suitable silts or clays are not economically available for the core, a concrete or bituminous facing is generally employed for the watertightness. As the facings deteriorate, water infiltration increases. With age and increased water infiltration, drains may become clogged because of transported fines. Uplift pressures will increase and dangerous internal erosion and potential piping of the dam may occur. The installation of a synthetic geomembrane on the upstream face, with a drainage system behind, provides the following benefits: stops water infiltration provides watertightness even when large settlements occur can withstand seismic events reduces/prevents the formation of uplift pressures avoids the migration of fines in the core prevents internal erosion and piping In addition to being used as a remedial measure on both concrete and bitumen faced dams, the ??? CARPI geomembrane system has been specified on new rockfill dams, up to 90 m (270 ft) high as the only watertight element on the upstream face. In these cases, the flexible synthetic geomembrane facing can be a valid alternative to a clay core providing the function of watertightness while aggregates of even less stringent properties provide structural stability. This solution may make projects feasible even when suitable aggregates are not available at competitive cost. CARPI experience includes also the lining of the upstream face of cofferdams. Sa Forada, Italy, 1992 Rouchain, France, 1999 Bovilla, Albania, 1996 Moravka, Czech Republic, 2000 Winscar, UK, 2001 Salt Spring, USA, 2005 Sabrina, USA, 2006 Karagjol, Bulgaria, 2006