Dispersive clay, with unique specification, is highly susceptible to erosion in certain circumstances. The erosion of the core of embankment dams in which dispersive clay are used can be usually led to hazardous occurrence. The primary factor contributing the susceptibility of a clay mass to erosion is the percent of sodium and other dissolved salts. The thickness of the double layer, which mainly depends on the type of clay soil, is another factor affecting the dispersivity phenomena. The existence cracks in dispersive clay core of embankment dams can also speed up erosion. Replacement of dispersive soil with a non-dispersive one, with highly costs, may be considered as the first solution. To improve the resistance of compacted dispersive clay to erosion there are many methods, of which using additives such as lime is the most common one. Adoption a suitable filter in clay core can also reduce the susceptibility to erosion. In the present research, different additives, including lime, sulfate aluminum and poly vinyl alcohol (PVA), are employed to examine the reduction of the dispersive tendency of three samples of dispersive clay, taken from different parts of North of Iran. It is shown that there is no unique solution for improvement of dispersive clay, but depends on the clay mineralogy and total dissolved salts (TDS) and sodium absorption ratio (SAR). It is also concluded that sulfate aluminum is more suitable than lime and PVA, since PVA is a very cohesive material in the presence of water and reduces the workability of clay soil.

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