مطالعه آزمایشگاهی تأثیر مشخصات سیال منفذی بر رفتار هسته رسی سدهای خاکی از منظر ریزساختاری

نوع مقاله : مقاله کامل پژوهشی

نویسندگان

گروه مهندسی عمران، دانشکده مهندسی، دانشگاه هرمزگان، بندرعباس

چکیده

پیدایش و انحلال نمک‌های محلول در مخزن سدهای خاکی از مسائل مهم در طراحی مخزن سدها است که می­تواند موجب تغییر رفتار در هسته رسی شود. این تغییرات رفتاری ممکن است باعث ایجاد خطرات عمده برای سازه سدهای خاکی شود. از این­ رو هدف پژوهش حاضر بررسی تأثیر نمک‌های محلول (سیال منفذی) بر رفتار ژئوتکنیکی هسته رسی سدهای خاکی با نگرش به تغییرات ضریب نفوذپذیری از منظر ریزساختاری است. در این راستا سیال منفذی سدیم کلرید (NaCl) با 8 غلظت مختلف (0، 02/0، 04/0، 08/0، 2/0، 4/0، 8/0 و 7/1 مولار) به خاک موردمطالعه افزوده شده است و مکانیزم تغییر رفتار ژئوتکنیکی هسته رسی تحت تأثیر نمک­ های محلول با نگرش به تغییرات حدود اتربرگ (Atterberg Limits)، تغییرات پارامترهای مقاومتی، تغییرات ضریب نفوذپذیری و بررسی احتمال پدیده واگرایی موردبررسی قرار گرفته است. همچنین برای ارزیابی تأثیر تغییر مشخصات سیال منفذی بر مشخصات ژئوتکنیکی خاک از منظر ریزساختاری، آزمون ارزیابی پراش پرتو ایکس ((XRD) X-ray Diffraaction) و تصویر میکروسکوپ الکترونی پویشی (SEM) از نمونه‌ها تهیه و مورد تجزیه‌وتحلیل قرار گرفته است. براساس نتایج پژوهش حاضر به‌طورکلی پیدایش و انحلال نمک‌های محلول در مخزن سدهای خاکی هرچند در کوتاه‌مدت ممکن است باعث کاهش 70% ضریب نفوذپذیری شود اما در درازمدت و با تغییر غلظت نمک موجود در مخزن ممکن است میزان ضریب نفوذپذیری تا 9 برابر افزایش یابد. در حقیقت براساس تصاویر میکروسکوپ الکترونی پویشی و آنالیز پراش اشعه ایکس رسوب بلورهای نمک، مانند هالیت (Halite) در کوتاه‌مدت موجب کاهش نفوذپذیری می‌شود. از سوی دیگر تشکیل ساختار مجتمع و شسته شدن بلورهای نمک هالیت رسوب‌کرده در ساختار موجب افزایش ضریب نفوذپذیری در درازمدت شده است.

کلیدواژه‌ها


عنوان مقاله [English]

An Experimental Study on The Effects of Pore-Fluid Parameters on Microstructural Behavior of Clay Core Materials in Embankment Dams

نویسندگان [English]

  • Mohammad Amiri
  • Rahim Zare
University of Hormozgan, Faculty of Engineering, Bandar Abbas, Iran
چکیده [English]

The abundance of saline water at ground level and their progression to freshwater and onshore sources, landfill leachate chemicals, or industrial plant effluents into the soil are factors that can change the amount and type of soil salinity and, as a result, their geotechnical properties (Ouhadi et al, 2015). Also, due to the size of the large dams reservoirs and the impossibility of changing the axis of the dams due to different constraints, it is possible that after the filling, the dam lake water will come into contact with the salt formations and may cause risks such as changing the geotechnical behavior of the clay core, after exploiting embankment dams. Therefore, due to the presence of contaminants, which is sometimes unavoidable, an understanding of basic mechanisms in modifying the physical and engineering properties of soils under the influence of chemicals or chemical salts is essential (Sen et al, 2017). In general, the concentration of ions affects the intermolecular forces of the soil (ie double-layer repulsion and van der Waals attraction) and the structure of the materials (Weimin et al, 2014; Zhu et al, 2015). As a result, such changes in soil structure alter its engineering properties (Yan and Chang, 2015). According to the extensive studies on the influence of pore fluid on clay soils, however, a comprehensive study from the microstructural perspective with regard to permeability coefficient changes on clay soils has not been conducted. The purpose of this study was to investigate the permeability coefficients and engineering properties of clay soils with a special attitude to clay core in the presence of sodium chloride solution salt as a pore fluid from a microstructural perspective.
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کلیدواژه‌ها [English]

  • Pore fluid
  • Embankment dams
  • Permeability
  • XRD
  • SEM
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