SMALL DAMS PETITS BARRAGES

sieves, 598 kg/m 3 through the 19 – 38mm sieves and 481 kg/m 3 through the 38-53mm sizes.
The 28 day 150mm cube strength of RCC was tested at 24.6 MPa. Drilled core results
revealed test strengths varying from 62.6 MPa to 30.9 MPa. The average density was 2443
kg/m 3 , average tensile strength 3.3 MPa, Average Elasticity Modulus 36.2 GPa, an average
Poisson’s ratio 0.16 and the average permeability 6.7 x 10 -7 cm/s.
2.6 CONCRETE BUTTRESS DAMS
Buttress dams are comprised of a flat deck and multiple arch structures or transversal
concrete buttresses as showed in Fig. 2.15, with only 7 m in height. They require about 60
percent less concrete than solid gravity dams, but the increased formwork and reinforcement
steel require usually offset the savings in concrete. A number of buttress dams were built in
the 1930’s, in United States, when the ratio of labor costs to material costs was comparatively
low. The cost of this type of construction is usually not competitive with that of other types of
dams when labor costs are high.
Approximately 400 concrete buttress dams of all types were constructed in the United
States. Of that number only 207 are in existence today, many of which are less than 9 m in
height.
2.7 GABION DAMS
Fig. 2.15 – Barra Buttress Concrete dam, Brazil.
First gabion retaining structures project was constructed in 1893 to retain the river banks
of the River Reno, in Italy. The use of gabion for the construction of small dams is more
recent, but the Chinese employ this technique with bamboo mesh baskets probably for a long
time.
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