University of Tabriz Water and Soil Science 2008-5133 29 1 2019 03 21 Experimental Investigation of Self-healing Phenomenon of Clay in Earth Dams and its Influencing Factors Experimental Investigation of Self-healing Phenomenon of Clay in Earth Dams and its Influencing Factors 15 25 8831 FA K Roushangar Assoc. Prof., Dept. of Water Eng., Faculty of Civil Eng., University of Tabriz, Iran M.T Alami Prof., Dept. of Water Eng., Faculty of Civil Eng., University of Tabriz, Iran Y Houshyar PhD Candidate in Hydraulic Structures. University of Tabriz, Tabriz, Iran Journal Article 2019 05 21 Compact clay layers are the most impermeable layers in earth dams. One of the most important factors in the failure of earth dams is the piping that the existence of cracks in the dam core is one of the major reasons for the formation of this phenomenon. Due to the nature of clay and its unique geotechnical properties, these layers are damaged over time by cracking. The cracks healing property in clays closes its external cracks. Self-healing of clays has been considered by researchers as one of the positive characteristics of clays. In this research, a new method is presented to assess the self-healing of clays using pinhole test. In order to reach the appropriate range of plasticity index (7<PI<26), three soil samples are prepared from the Vanyar dam borrow pit as follows: first sample with 10% bentonite, second sample with 20% bentonite and third one just natural soil. The results showed that by adding bentonite, for optimum moisture content and 2% below, soil dispersion reduced and the soil became non-dispersive. Moreover, self-healing phenomenon was visible and predictable with increasing of bentonite in the natural soil. This phenomenon was observed for 20% bentonite having high plasticity index and swelling from early age. The sample with 20% bentonite and moisture content 2% lower than optimum showed the most reduction in outflow (38%) compared to the natural soil sample. Thus, plasticity index increment in the suitable range could cause the non-dispersivity of clay and increasing of self-healing ability. Compact clay layers are the most impermeable layers in earth dams. One of the most important factors in the failure of earth dams is the piping that the existence of cracks in the dam core is one of the major reasons for the formation of this phenomenon. Due to the nature of clay and its unique geotechnical properties, these layers are damaged over time by cracking. The cracks healing property in clays closes its external cracks. Self-healing of clays has been considered by researchers as one of the positive characteristics of clays. In this research, a new method is presented to assess the self-healing of clays using pinhole test. In order to reach the appropriate range of plasticity index (7<PI<26), three soil samples are prepared from the Vanyar dam borrow pit as follows: first sample with 10% bentonite, second sample with 20% bentonite and third one just natural soil. The results showed that by adding bentonite, for optimum moisture content and 2% below, soil dispersion reduced and the soil became non-dispersive. Moreover, self-healing phenomenon was visible and predictable with increasing of bentonite in the natural soil. This phenomenon was observed for 20% bentonite having high plasticity index and swelling from early age. The sample with 20% bentonite and moisture content 2% lower than optimum showed the most reduction in outflow (38%) compared to the natural soil sample. Thus, plasticity index increment in the suitable range could cause the non-dispersivity of clay and increasing of self-healing ability. https://water-soil.tabrizu.ac.ir/article_8831_bfee3af67ac633285802d5dfd11f083f.pdf