SMALL DAMS PETITS BARRAGES

material has been left in place or has not been treated beyond the dam’s upstream and
downstream toes. In the case of sandy layers, classic treatment consists in building a mesh of
vertical drains (to drain overpressures generated by the earthquake) or in improving the
ground by densifying it.
For the fill, modifications may be necessary to deal with any internal problems and
strains that may occur. Generally, a probable consequence of a strong earthquake is the
appearance of concentrated leakage through the dam. Such modifications concern zoning of
the fill, resistance of the materials to retrogressive erosion, and design of the crest. The
following precautions are worth mentioning:
� Avoid fine, cohesion less and uniform soil in saturated zones;
� Provide a chimney drain or enlarge it in the case of homogeneous fills;
� Design transition zones that are as wide as possible;
� Be specially prudent with the thickness of filters;
� Place a layer of sand upstream from the core to plug any cracks that may be caused
by an earthquake;
� Build the dam or its core with materials offering good resistance to internal erosion
(plastic clays, sandy gravel with fines of a very continuous grading).
In addition, as recommended by the French Guidelines, if the design earthquake
intensity is very strong, it may be wise to increase freeboard and crest width.
5.13 REFERENCES
[1] CHINCOLD (1979) – Dam Construction by the Chinese People, The Chinese National
Committee on Large Dams;.
[2] SHERARD, J.L., DUNNIGAN, L.P. (1985) – “Filters and Leakage Control in
Embankment Dams”, Proc. Symposium on Seepage and Leakage from Dams, ASCE.
[3] Bureau of Reclamation (1987) – Design of Small Dams, United States Department of the
Interior, A Water Resources Technical Publication;
[4] LEWIS, B. (2002) – Farm Dams – Planning, Construction and Maintenance, National
Library of Australia Cataloguing;
[5] CEMAGREF (2002) – Small Dams – Guidelines for Design, Construction and
Monitoring, French Committee on Large Dams;
[6] DURAND JM, ROYET P, MÉRIAUX P (2002) – Technique des Petits Barrages en
Afrique Sahélienne et Équatoriale, Cemagref Editions.
[7] SMEC (2006) – Draft Guidelines for Managing Small Dams, SMEC Australia Pty Ltd,
Guide developed on behalf of The Republic of Uganda.
[8] JSIDRE (2006) – The Guidelines for Designing of Agricultural Land Improvement
Projects, “Tameike Small Dams”, Japanese Society of Irrigation, Drainage and
Reclamation Engineering, February 2006.
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