Experimental investigation of bentonite impact on self-healing of clay soils

Abstract

Compacted clay layers are known as earth dams’ most common impermeable layer. However, owing to the specific nature of clay and Atterberg limits, an increase in age damage, these layers by cracking them. Despite this, the crack-healing property of clay is the main factor in closing external cracks. In this regard, in this study, a new method is used to evaluate clays’ self-healing characteristic by pinhole tests with the variation of the Plasticity Index (PI). For this purpose, three soil samples from the Vanyar Dam located in Iran were treated to obtain the PI between 7 and 26 by adding different percentages of bentonite (i.e., 5%, 10%, 15%, and 20%) and the impact of bentonite percentage increase was investigated on self-healing property and outflow rate of clay soil. Subsequent to geotechnical tests, the obtained results showed that adding bentonite to the soil samples with optimum water content and 2% below it, decreases soil dispersion and makes it non-dispersive. In addition, the self-healing phenomenon was visible and predictable with the increase of bentonite in natural soil; as for the sample with 20% bentonite, this phenomenon was observed from an early age due to high PI and the potential for high inflation. Also, the sample with 20% bentonite and a moisture content of 2% less than the optimum showed the most reduction in the outflow (38%) when compared with the natural soil sample. Therefore, it can be concluded that the PI variation (between 7 and 26) can cause non-dispersivity of clay and increase the self-healing ability.