Experimental investigation of bentonite impact on self-healing of clay soils
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ORIGINAL PAPER
Experimental investigation of bentonite impact on self-healing of clay soils Kiyoumars Roushangar 1,2 & Mohammad Taghi Alami 1 & Yagoub Houshyar 1 Received: 29 October 2017 / Accepted: 7 October 2020 # Saudi Society for Geosciences 2020
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. Keywords Pinhole test . Bentonite . Clay . Self-healing . Core
Introduction Piping is the primary cause of failure in most earth dams that is the internal erosion of soil mass which causes seepage and water discharge through holes and appears in the downstream of the embankment (Moffat et al. 2011). Foster et al. (2000a, b) noted that failure can occur in 6–12 h. Hence, this issue should be accounted for when designing hydraulic-soil structures to ensure their safety, as piping can be a dangerous failure phenomenon in soil embankments and earth dams (Fell et al. 2003). Meanwhile, dispersive clays and dispersion Responsible Editor: Zeynal Abiddin Erguler * Kiyoumars Roushangar [email protected] 1
Department of Civil Engineering, University of Tabriz, Tabriz, Iran
2
Center of Excellence in Hydroinformatics, University of Tabriz, Tabriz, Iran
of soil are the primary factors that cause piping. In small earth dams, piping failures caused by the dispersive nature of clays have been widely reported in all the states of Australia (Aitchison and Wood 1965), the USA (Sherard et al. 1972), and other parts of the world. Sherard and Decker (1977) believe that dispersive clay particles are the type of soils that are mostly subject
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