Evaluation of Influencing Factors in Outflow Control and Self-healing Property of Clay Core (case study: Vanyar dam- Iran)

Document Type : Original Article


Department of Water Resources Engineering, Faculty of Civil Engineering, University of Tabriz, Tabriz, Iran


Compacted clay layers are the most common impermeable layers of earth dams. Due to the specific nature of clay and its unique geotechnical properties, these layers are damaged over time by cracking. The crack healing property of clay is its ability to close up its external cracks and reduce the outflow rate. Hence, in this study, a new method is presented to assess the self-healing phenomenon of clays using pinhole test. In this regard, three soil samples from Vanyar dam (Iran) were treated to obtain the Plasticity Index (PI) between 7 to 26. Different percent of bentonite was added to samples (i.e. 5%, 10%, 15%, 20%) and the impact of bentonite percentage increasing was investigated on self-healing property and outflow rate of clay soil. The obtained results showed that soil dispersion reduced and it became non-dispersive when bentonite was added to the soil samples with the optimum water content and 2% below it. Self-healing phenomenon was visible and predictable with the increase of bentonite in natural soil. For the sample with 20% bentonite, this phenomenon was observed from an early age due to high PI and the potential for high inflation. The sample with 20% bentonite and a moisture content of 2% less than the optimum showed the most reduction in outflow (38%) when compared with the natural soil sample. Therefore, it can be concluded that the PI increment for mixed bentonite-clay soil (between 7 to 26) can increase the self-healing ability.


[1]-Moffat, R., Fannin, R. J., and Garner, S. J., 2011, Spatial and temporal progression of internal erosion in cohesionless soil, Canadian Geotechnical Journal, 48, 399-412.
[2]-Foster, M., Fell, R., and Spannagle, M., 2000a, A method for assessing the relative likelihood of failure of embankment dams by piping, Canadian Geotechnical Journal, 37, 1025-1061.
[3]-Foster, M., Fell, R., and Spannagle, M., 2000b, The statistics of embankment dam failures and accidents, Canadian Geotechnical Journal, 37, 1000-1024.
[4]-Fell, R., Wan, C. F., Cyganiewicz, J., and Foster, M., 2003, Time for development of internal erosion and piping in embankment dams, Journal of Geotechnical and Geoenvironmental Engineering, 129, 307-314.
[5]-Aitchison, G., and Wood, C., 1965, Some interactions of compaction, permeability, and post-construction deflocculation affecting the probability of piping failure in small earth dams, Proc. International Conference on Soil Mechanic And Foundation Engineering, 2, 442–446.
[6]-Sherard, J. L., Decker, R. S., and Ryker, N. L., 1972, Piping in earth dams of dispersive clay, In: Performance of Earth and Earth-Supported Structures, ASCE, 589.
[7]-Sherard, J. L., and Decker, R., 1977, Summary—Evaluation of Symposium on Dispersive Clays. In:  Dispersive Clays, Related Piping, and Erosion in Geotechnical Projects, ASTM International.
[8]-Honjo, Y., and Veneziano, D., 1989, Improved filter criterion for cohesionless soils, Journal of Geotechnical Engineering, 115, 75-94.
[9]-Eigenbrod, K., 2003, Self-healing in fractured fine-grained soils, Canadian Geotechnical Journal, 40, 435-449.
[10]-Bendahmane, F., Marot, D., and Alexis, A., 2008, Experimental parametric study of suffusion and backward erosion, Journal of Geotechnical and Geoenvironmental Engineering, 134, 57-67.
[11]-Vekli, M., Çadır, C. C., and Şahinkaya, F., 2016, Effects of iron and chrome slag on the index compaction and strength parameters of clayey soils, Environmental Earth Sciences, 75, 5, 425
[12]-Kakuturu, S., and Reddi, L. N., 2006a, Evaluation of the parameters influencing self-healing in earth dams, Journal of Geotechnical and Geoenvironmental Engineering, 132, 879-889.
[13]-Kakuturu, S., and Reddi, L. N., 2006b, Mechanistic model for self-healing of core cracks in earth dams, Journal of Geotechnical and Geoenvironmental Engineering, 132, 890-901.
[14]-Chinn, C, and Pillai, U., 2008, Self-repair of compacted Vertisols from central Queensland, Australia, Geoderma 144, 491-501.
[15]-Wang, J. J., Zhang, H. P., Zhang, L., and Liang, Y., 2013, Experimental study on self-healing of crack in clay seepage barrier, Engineering Geology, 159, 31-35.
[16]-Chai, J. C., Sari, K., Shen, S. L., and Cai, Y., 2016, Predicting self-healing ratio of GCL with a damage hole, Geotextile and Geomembrane, 44, 761-769.
[17]-Rowe, R. K., and Li, T., 2016, A Preliminary Study of the Bentonite Self-healing of Slits in a GCL upon Full Hydration, Geosynthetics, Forging a Path to Bona Fide Engineering Materials, 116-125
[18]-Egloffstein, T. A., 2001, Natural bentonites-the influence of the ion exchange and partial desiccation on permeability and self-healing capacity of bentonites used in GCLs, Geotextile and Geomembrane, 19, 427-444.
[19]-Li, T., and Rowe, R. K. A., 2017, Preliminary Study of the Self-Healing of a Fully Penetrating Hole in GCLs on Full Hydration, Geotechnical Frontiers, 278-287.
[20]-Seed, H. B., Woodward, Jr., and Lundgren, R., 1962, Prediction of Swelling Potential for Compacted Clays, Journal of Soil Mechanics and Foundation Division, 88, 53-88.