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Behavioral evaluation of earth dams built with materials above optimum moisture content in high rainfall areas

Abstract:

South Americas topographic characteristics and available materials have led engineers to select earth or rockfill material for dams construction. However, there are tropical re-gions with high annual rainfall where the soil compaction above the optimum moisture must be studied in detail. This research presents the results of tests performed on compacted soil samples, with water contents of +2 % and +5 % above the optimum moisture. Such samples were classified as low plasticity sandy silt by the USCS and as sandy lateritic clay by MCT methods. The investigation analyses a seepage, slope stability, and stress-strain numerical analysis conducted on typical hypothetical homogeneous and heterogeneous dams. In general terms, the heterogeneous sections showed adequate behavior for all the modeled soils. However, the slopes of the homogeneous sections exhib-ited low safety factors during the rapid drawdown of the reservoir water level. The material compacted above the optimum water content presented a superior performance to dissipate pore water pressure along the time than the other soils. Concluding that the use of soil above the optimum can be convenient and economical for dam construction, in the case where no other material is available, and a fast pore water relief is sought.