تأثیر هیدراتاسیون اولیه بنتونیت بر تغییر خصوصیات خمیری آن در اندرکنش با آلاینده آلی
محورهای موضوعی : آلودگی خاک
وحیدرضا اوحدی
1
(
استاد دانشکده مهندسی عمران، دانشگاه بوعلی سینا؛ عضو هیئت علمی وابسته دانشکده عمران، دانشگاه تهران * (مسوول مکاتبات)
)
زینب آقایی
2
(
کارشناس ارشد مهندسی عمران-ژئوتکنیک، پردیس دانشکدههای فنی، دانشگاه تهران
)
کامبیز بهنیا
3
(
دانشیار دانشکده مهندسی عمران، پردیس دانشکدههای فنی، دانشگاه تهران.
)
کلید واژه: سدیم-بنتونیت, ثابت دیالکتریک, هیدراتاسیون اولیه, آلاینده آلی,
چکیده مقاله :
زمینه و هدف: آستر خـاک رسی متـراکم (CCLs) به دلیــل ضریب نفـوذپذیری کم و قـابلیت مناسب در جـذب و نگــهداری آلاینــده، در مراکـز دفن مهندسی زبالـه مورد استفـاده قرار می گیرد. تغییر ویژگی‌های سیـال منفذی در خاک، تــأثیر بسزایی بر مشخصات مهندسی و رفتــاری خاک های رسی دارد. با وجود تحقیقاتی که در خصوص فرآیند اندرکنش رس و مــواد آلی صورت گرفتـه، در زمینه تأثیـر هیدراتاسیون اولیه بنتونیت و تغییــر در ثابت دیالکتریک آلاینده آلی بر خصوصیــات ژئوتکنیکی و ژئوتکنیک زیستمحیطی بنتونیت تحقیقـات محدودی انجام شده است. در حالی‌که چنین فرآیند اندرکنشی در بسیـاری از پروژه‌هـای صنعتی و دفن مهندسـی زباله به عنوان یک عملکرد مورد انتظار به وفور رخ می‌دهد. روش بررسی: در این تحقیق از خـاک سدیم-بنتونیت در معرض 2 نوع مـاده آلی (اتـانول و اسیـد استیک) بـا ثـابت دی الکتریک مختلف تحت شـرایط هیـدراتـاسیونی متفـاوت استفـاده شـده‌است. پس از حصـول تعـادل، تـأثیـر فرآینـد هیـدراتـاسیون اولیـه و همچنین تغییـر در ثـابت دیالکتریک بر خصوصیات خمیری بنتونیت در اندرکنش با مواد آلی توسط آزمایش حدود اتربرگ مورد بررسی آزمایشگاهی قرارگرفته است. یافته‌ها: نتـایج حـاکی از آن است کـه در نمـودار خمیـری کاسـاگرانده، نمونـه‌های سدیم-بنتونیت بـا هیدراتـاسیون اولیـه و قـرار گرفتـه در معرض اتانول و اسید استیک به ترتیب، همچنان به عنوان خاک CH و انتقال یافته از ناحیه CH به MH طبقه بندی شده‌اند. نتیجه‌گیری: تغییر در ثابت دی الکتریک و شرایط متفاوت هیدراتاسیونی منجـر به تغییـر در ضخامت لایه دوگانه شده است که این عامل، موجب تغییرات قـابل توجهی در ساختار و تغییر رفتار خاک رسی شده است. این تغییرات بر اساس روابط تئوریک موجود مورد تجزیه و تحلیل قرار گرفته و محـدودیت های نظری در روابط تئـوریک در تفسیـر پـاسخ های خـاک به تفکیـک بحث شده اند.
Background and Objective: The compacted clay liners (CCLs) due to their low permeability and suitable capability for contaminant retention are widely used in engineering waste disposal sites. Generally, the change in properties of soil pore fluid has a very distinguished impact on the behaviour of clayey soils. In spite of several researches, which have been performed on the process of clay and organic contaminant interaction, there are few researches on the influence of dielectric constant of organic contaminant and initial hydration of bentonite on the geotechnical and geo-environmental properties of organic contaminated bentonite. Such a process is very common in many industrial and waste disposal projects. Methods: This research was performed on sodium-bentonite soil samples which were exposed to two different organic materials (Ethanol and Acetic Acid) which have different dielectric constant. Furthermore, two different pre-hydration and post-hydration conditions were studied in this research. After achieving equilibrium condition, the influence of initial hydration and change on the dielectric constant of pore fluid upon interaction of organic material and bentonite was investigated. The investigation focuses attention on the plasticity properties of bentonite by the use of Atterberg limit tests. Findings: The achieved results indicate that in Casagrande's plasticity chart, two pre-hydrated sodium-bentonite soil samples which were exposed further to ethanol and acetic acid are classified as CH and shifted from CH to MH, respectively. Discussion and Conclusion: The change on the dielectric constant of pore fluid and different hydration conditions cause a change on the thickness of the double layer of clay fraction of the soil. This causes a noticeable change on the structure and behaviour of clay fraction of the soil sample. This variation on bentonite behaviour has been discussed based on the current available theory of double layer. Furthermore, the theoretical limitation for interpretation of results has been addressed.
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- Di Maio, C., 1996. Exposure of bentonite to the salt solution: osmotic and mechanical effects. Geotechnique, Vol. 46, pp. 695–707.
- Wang, Y.H., Siu, W.K., 2006. Structure characteristics and mechanical properties of kaolinite soils. I. Surface charges and structural characterizations. Can. Geotech. J, Vol. 43, pp. 587–600.
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- Li, J.S., Xue, Q., Wang, P., Liu, L., 2013. Influence of leachate pollution on mechanical properties of compacted clay: a case study on behaviors and mechanisms. Eng. Geol, Vol. 167, pp. 128–133.
- Li, Z., Katsumi,T., Inui, T.,Takai, A., 2013. Fabric effect on hydraulic conductivity of kaolin under different chemical and biochemical conditions. Soils Found, Vol. 53, pp. 680–691.
- Sridharan, A., El-Shafei, A., Miura, N., 2000. A study on the dominating mechanisms and parameters influencing the physical properties of Ariake clay. International Association of Lowland Technology Journal, Vol. 2, pp. 55–70.
- Olgun, M., and Yıldız, M., 2010. Effect of organic fluids on the geotechnical behavior of a highly plastic clayey soil. Vol, 48, pp. 615-621.
- Yong, R.N., Warkentin, P.B., 1966. Introduction to soil behavior. Mc Millan Co., London, p. 451.
- Liu, Y., Gates, W.P., Bouazza, A., 2013. Acid induced degradation of the bentonite component used in geosynthetic clay Liners. Geotextiles and Geomembranes, Vol. 36, pp. 71-80.
- Spagnoli, G., Stanjek, H., and Sridharan, A., 2012. Influence of ethanol/water mixture on the undrained shear strength of pure clays. Bulletin of Engineering Geology and the Environment, Vol. 71, pp. 389-398.
- Hendershot W.H., Duquette M., 1986. A simple barium chloride method for determining cation exchange capacity and exchangeable cations, Soil Sci. Soc. Am. J., Vol. 50, pp. 605-608.
- Ouhadi, V.R., Amiri, M., 2014. Interaction of Nano-Clays and Cu Contaminant in Geo-Environmental Projects. Journal of Environmental Science and Technology, Vol. 16 (160), 75-87
- Ouhadi, V.R., Amiri, M., 2011. Geo-environmental Behaviour of Nanoclays in Interaction with Heavy Metals Contaminant, Amirkabir Journal of Civil Engineering, Vol. 42, Issue 3, pp 29-36.
- Moavenian, M.H., Yasrobi, SH. S., 2008. Volume change behavior of compacted clay due to organic liquids as permeant. Applied Clay Science, Vol. 39, pp. 60-71.
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- Ouhadi, V.R., Goodarzi, A.R., 2007. Factors impacting the electro conductivity variations of clayey soils. Iranian Journal of Science & Technology, Transaction B: Engineering, Vol. 31, pp. 109-121.
- Mitchell, J. K., 1960. The application of colloidal theory to the compressibility of clays. Commonwealth Science and Industry Research Organization, Melbourne, Australia, Vol. 2, pp. 92-97.
- Ouhadi, V.R., Amiri, M., Goodarzi, A.R., 2012. The Special Potential of Nano-Clays for Heavy Metal Contaminant Retention in Geo-Environmental Projects, Journal of Civil and Surveying Engineering, Vol: 45, Issue: 6, pp. 631-642.
- Sridharan, A., Rao, G.V., 1975. Mechanisms controlling the liquid limit of clays. Prof. Int. Conference on SMQFE, Istanbul,Vol. 1, pp. 65–74.
- Ouhadi, V.R., Amiri, M., 2009. Interaction of Nano-Clays and Cu Contaminant in Geo-Environmental Projects. 6th Conf. Engineering Geology, Tarbiat Modares University, Tehran.
- Yanful, E.K., Shikatani, K.S., Quirt, D.H., 1995. Hydraulic conductivity of natural soils permeated with acid mine drainage. Can. Geotech. J., Vol. 32, pp. 624–646.
- Di Maio, C., 1996. Exposure of bentonite to the salt solution: osmotic and mechanical effects. Geotechnique, Vol. 46, pp. 695–707.
- Wang, Y.H., Siu, W.K., 2006. Structure characteristics and mechanical properties of kaolinite soils. I. Surface charges and structural characterizations. Can. Geotech. J, Vol. 43, pp. 587–600.
- Xue, Q., Zhang, Q., Liu, L., 2012. Impact of high concentration solutions on hydraulic properties of geosynthetic clay liner materials. Materials, Vol. 5, pp. 2326–2341.
- Li, J.S., Xue, Q., Wang, P., Liu, L., 2013. Influence of leachate pollution on mechanical properties of compacted clay: a case study on behaviors and mechanisms. Eng. Geol, Vol. 167, pp. 128–133.
- Li, Z., Katsumi,T., Inui, T.,Takai, A., 2013. Fabric effect on hydraulic conductivity of kaolin under different chemical and biochemical conditions. Soils Found, Vol. 53, pp. 680–691.
- Sridharan, A., El-Shafei, A., Miura, N., 2000. A study on the dominating mechanisms and parameters influencing the physical properties of Ariake clay. International Association of Lowland Technology Journal, Vol. 2, pp. 55–70.
- Olgun, M., and Yıldız, M., 2010. Effect of organic fluids on the geotechnical behavior of a highly plastic clayey soil. Vol, 48, pp. 615-621.
- Yong, R.N., Warkentin, P.B., 1966. Introduction to soil behavior. Mc Millan Co., London, p. 451.
- Liu, Y., Gates, W.P., Bouazza, A., 2013. Acid induced degradation of the bentonite component used in geosynthetic clay Liners. Geotextiles and Geomembranes, Vol. 36, pp. 71-80.
- Spagnoli, G., Stanjek, H., and Sridharan, A., 2012. Influence of ethanol/water mixture on the undrained shear strength of pure clays. Bulletin of Engineering Geology and the Environment, Vol. 71, pp. 389-398.
- Hendershot W.H., Duquette M., 1986. A simple barium chloride method for determining cation exchange capacity and exchangeable cations, Soil Sci. Soc. Am. J., Vol. 50, pp. 605-608.
- Ouhadi, V.R., Amiri, M., 2014. Interaction of Nano-Clays and Cu Contaminant in Geo-Environmental Projects. Journal of Environmental Science and Technology, Vol. 16 (160), 75-87
- Ouhadi, V.R., Amiri, M., 2011. Geo-environmental Behaviour of Nanoclays in Interaction with Heavy Metals Contaminant, Amirkabir Journal of Civil Engineering, Vol. 42, Issue 3, pp 29-36.
- Moavenian, M.H., Yasrobi, SH. S., 2008. Volume change behavior of compacted clay due to organic liquids as permeant. Applied Clay Science, Vol. 39, pp. 60-71.
