Effect Of Moisture Content, Dry Density And Curing Time On The Erosion Resistance Of Two River Nile Deposits

Abstract

Geotechnical engineers recognized dispersive soils in the last century while investigating failures of many earth dams around the world. When these soils are blindly used in the construction of embankments or encountered in dam foundations, they greatly increase the risk of piping and lead in many instances to failures. Nevertheless, dispersive soils have been successfully used in construction of earth fills provided that suitable defensive design details, especially fine filters and high care for construction quality control, are adopted. In this study, erodibility and dispersivity of two River Nile alluvial soils, proposed for use as core material for Merowe Dam, were investigated to study the effects of compaction water content, dry density and curing time on their erosion resistance. One of the samples was rendered slightly dispersive (Sample A), while the other one was highly dispersive (Sample B). The study was performed by preparing compacted specimens with different moisture contents and dry densities using a split mould especially manufactured to have internal dimensions similar to the cylindrical pinhole test specimen. The pinhole test for dispersivity was used to assess the erosion resistance of the compacted specimens after being allowed to cure for different periods of time. The results of the study indicate that the higher the dry density and moisture content and the longer the curing period, the better is the erosion resistance for the slightly dispersive Sample (A) material, and that the improvement with time is more for the lower moisture contents and IV densities. The erosion resistance of the highly dispersive Sample (B) material improved very slightly after more than one year of curing for the specimen with the highest bulk density and relatively low air voids.