Effect of Leachate pH on the Collapse Potential and Shear Strength Parameters of Collapsible Soils

Document Type : Research Article


Civil Engineering Department, Shahrood University of Technology, Semnan, Iran


Collapse soils have a stable loose honeycomb-type structure in a low degree of saturation which is susceptible to a large reduction in total volume or collapse upon wetting. The aim of this study is to evaluate the collapse potential and shear strength parameters due to saturation of soil caused by the infiltration of contaminants including leachate wastewater and chemicals into the soil. Since the separation of leachate components is difficult, especially with change of ingredients and pH in long time, the two factors sulfuric acid and sodium hydroxide were used as representatives of the leachate in the pH of 1 to 14. Furthermore, collapse tests and direct shear tests were performed on soil samples which were saturated by leachate. Experimental results show that leachate with a low pH or acidic solutions increase the soil collapse potential; on the other hand, leachate with a high pH or alkaline solutions cause less soil collapse. Variation range of soil collapse in acidic solution was much more than alkaline solution. Direct shear test results demonstrate that acidic leachate increase the soil cohesion and reduce the internal friction angle of soils; however, alkaline leachate reduce the soil cohesion and increase the friction angle of soils.


Main Subjects

[1] V. Saeed, A. Kongi, The effect of rising of sewage of Kerman city on the increasing of potential of soil collapse, in: 8th Conference of the Iranian Association of Engineering Geology and the Environment, Fredowsi University of Mashhad, 2013.
[2] M.M. Ahmadi, M. Hasanlourad, M.H. Khatami, An Investigation of the effect of Variation in the pH of Leachate on the Physical and Mechanical Properties of Kaolinite clay soil in presence Bentonite, Journal of Experimental Research in Civil Engineering (JERCE), Volume 2(Issue 2) (2015) Page 25-33
[3] W. Huang, W. Keller, Dissolution of clay minerals in dilute organic acids at room temperature, American Mineralogist: Journal of Earth and Planetary Materials, 56(5-6) (1971) 1082-1095.
[4] A. Mahdavi, The effect of Variation in the pH on some mechanical parameters of clay, Azad University of Arak, 1997.
[5] Y.-H. Wang, W.-K. Siu, Structure characteristics and mechanical properties of kaolinite soils. I. Surface charges and structural characterizations, Canadian Geotechnical Journal, 43(6) (2006) 587-600.
[6] C.H. Benson, H. Zhai, X. Wang, Estimating hydraulic conductivity of compacted clay liners, Journal of geotechnical engineering, 120(2) (1994) 366-387.
[7] S. Goldberg, H. Forster, S. Lesch, E. Heick, Influence of anion competition on boron adsorption by clays and soils, Soil Science, 161(2) (1996) 99-103.
[8] M. James, Chemical Effects on clay Hydraulic conductivity, 1995
[9] M.H. Sedghiani, A. Qadak, The effect of Variation in the pH on the strength properties of clay, in: 1st National Congress on Civil Engineering, Sharif University of Technology, 2004.
[10] C. Ramakrishnegowda, R.K. Yaji, R. Shivashankar, P.V. Sivapullaiah, Geotechnical properties of shedi soil affected by alkali contamination, Indian J. Environ. Pollut, 1 (2011) 45-52.
[11] J.-s. Li, Q. Xue, P. Wang, L. Liu, Influence of leachate pollution on mechanical properties of compacted clay: a case study on behaviors and mechanisms, Engineering Geology, 167 (2013) 128-133.
[12] R. Hasan, H. Hasan, R. Islam, K.A.A. Razi, S. Alam, T. Abdullah, Changes in geotechnical properties of soil with pH in household and industrial waste dump site, International Journal of Applied Science and Engineering Research, 2(2) (2013) 119-127.
[13] B. Sunil, S. Shrihari, S. Nayak, Shear strength characteristics and chemical characteristics of leachate-contaminated lateritic soil, Engineering Geology, 106(1-2) (2009) 20-25.
[14] P. Pells, A. Robertson, J. Jennings, K. Knight, A guide to construction on or with materials exhibiting additional settlement due to" Collapse" of grain structure, 1975.
[15] L. Barden, A. McGown, K. Collins, The collapse mechanism in partly saturated soil, Engineering Geology, 7(1) (1973) 49-60.
[16] S.M. Haeri, A.A. Garakani, The variation of total volume change, water volume change, yielding net confining stress and shear strength of undisturbed unsaturated loess under isotropic compression, in: Unsaturated soils: Research and applications, Springer, 2012, pp. 293-300.
[17] ASTM.D. 4318-87, Standard test methods for liquid limit, plastic limit and plasticity of soils, in, 1987.
[18] ASTM.D. 854-92, Test method for specific gravity of soils, in, 1992.
[19] ASTM.D. 5333-03, Standard test methods for measurement of collapse potential of soils, in, 2003.
[20] ASTM.D. 3080, Standard Test Method for Direct Shear Test of Soils Under Consolidated Drained Conditions, in, 2011.