Document Type : Research Note
Authors
1
Dept. of Water Engineering Shiraz University
2
Dept. of Engineering Islamic Azad University, Estahban
Abstract
Erodibility of soil is one of the most important factors when dealing with water based projects, such as earthen water canals, earthfill dams and other hydraulic structures. Erosion is the cause of much canal, dam or levee failure and its consequent loss of life and money. Thus, soil erosion has always been a field of interest among hydraulic and civil engineers, and much research has been undertaken in an attempt to find different methods of controlling this phenomenon. Stabilizing soil with chemical additives is the most common method of controlling erosion in fine grained soils, and different stabilizers with different stabilizing mechanisms are produced and used even now. CBR+, also known as CON-AID, is a nanotechnology product designed for stabilizing poor quality soils containing clayey material. This anionic soil stabilizer, originated from petroleum, is a viscous, deep red color liquid, with no smell or taste, which works on the basis of ion exchange. In this study, the effect of this product on the erosional behavior of clayey soils is investigated. For this purpose, specimens stabilized using different amounts of CBR+ were prepared and, after curing periods of 7, 14 and 21 days, their erosional behavior was compared with that of non-stabilized ones. Erosion tests were performed using a submerged jet erosion device (JET). According to the results obtained, different erosional behaviors are obtained when using equivalent values of 0.005, 0.007 and 0.009 litres of CBR+ per 0.15 cubic meters of tested soil. These behaviors vary in procedures of variations of erosion curve, mean erodibility coefficient ($k_d$), and critical shear stress ($\square_c$) of the specimens after the mentioned curing periods, and tend to the behavior of the non-stabilized specimens after 21 days. The cause of these variations in different stabilized specimens must be considered in different mechanisms by which CBR+ affects the soil. These are the most important factors controlling the erosional characteristics of soils, such as the changes of permeability of specimens, the degree of compaction which each stabilized specimen reaches by the same compaction effort, and the sensitivity of stabilized soil to water.Finally, it is concluded that the use of CBR+ cannot directly affect the erosional characteristics of soil. On the other hand, its secondary effects, such as an increase in the degree of compaction and permeability of soil and a decrease in its sensitivity to water, will highly affect the erosional characteristics of a clayey soil.
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