بررسی اثر ‌‌شوری آب بر خصوصیات فیزیکی و مکانیکی خاک‌های ریزدانه (مطالعه موردی سدهای شهید مدنی و ملکیان آذربایجان‌شرقی)

نوع مقاله : مقاله پژوهشی

نویسندگان

1 گروه مهندسی عمران، دانشکده فنی و مهندسی، دانشگاه شهید مدنی اذربایجان

2 مهندسی عمران- دانشکده فنی و مهندسی - دانشگاه شهید مدنی اذربایجان

3 گروه مهندسی عمران- دانشکده فنی و مهندسی - دانشگاه شهید مدنی آذربایجان - تبریز

4 گروه مهندسی عمران-دانشکده فنی و مهندسی-دانشگاه شهید مدنی تبریز - تبریز

چکیده

خاک‌های ریزدانه با درصد بالای کانی‌های رسی به علت نفوذ‌پذیری پایین در پوشش مدفن­های بهداشتی و هسته سدهای خاکی استفاده می‌شوند. یکی از عوامل مهم مؤثر بر رفتار این خاک‌ها، شیمی آب منفذی است، به طوری که تغییر در غلظت سیال و نوع کاتیون‌های آن، می‌تواند موجب تغییر خواص مهندسی خاک‌ها گردد. در تحقیق حاضر، اثر شوری آب بر ویژگی‌های خمیری، تراکم، مقاومت برشی و فشار آب‌حفره‌ای خاک‌های ریزدانه بررسی شده است. بدین منظور، آزمایش‌های حدود اتربرگ، تراکم و سه‌محوری زهکشی‌نشده بر روی مصالح ریزدانه مورد استفاده در هسته سدهای خاکی ملکیان و شهید مدنی با سیال‌های منفذی مختلف انجام گرفته است. آب‌های استفاده شده شامل آب مقطر، آب شور هر پروژه، و محلول‌های آب شور با غلظت‌های 2/0، 4/0 و 8/0 مولار نمک طعام بودند. نتایج نشان داد که با افزایش شوری آب، حد روانی، حد خمیری و نشانه خمیری اندکی کاهش می‌یابد، لیکن این تغییرات چندان قابل‌ملاحظه نمی‌باشند. نتایج آزمایش‌های سه‌محوری نشان داد که با افزایش شوری آب، مقاومت برشی نمونه‌های خاک همواره افزایش نمی‌یابد. حداکثر افزایش در مقاومت برشی خاک‌های ملکیان و مدنی با محلول 2/0 مولار بدست آمد، که به عنوان نقطه بهینه ذکر می‌شود. در هر دو خاک با افزایش شوری آب، فشار آب حفره‌ای اضافی کاهش یافته و روند مشخصی بر مدول تغییرشکل خاک‌ها ندارد. چسبندگی در هر دو خاک تا 4/0 مولار کاهش یافته و بعد از آن با بیشتر شدن شوری زیاد شده است. شوری آب در محدوده 2/0 الی 4/0 مولار، زاویه اصطکاک داخلی خاک‌ها را افزایش داده و بعد از آن اثر مثبتی بر روی این پارامتر ندارد. 

کلیدواژه‌ها

موضوعات

عنوان مقاله [English]

The Effect of Saline Water on the Physical and Mechanical Properties of Cohesive Fine-grained Soils (Case Study, Madani and Malekian Dams in East Azarbaijan Province)

نویسندگان [English]

  • Hossein Soltani-Jigheh 1
  • Nazila Kardan 2
  • Hussein Eshaghi 3
  • Mohammad Reza Emami Azadi 4
1 Department of Civil Engineering, Azarbaijan Shahid Madani University
2 Department of civil eng. Azarbaijan shahid madani University
3 Department of Civil Engineering- Azarbaijan Shahid Madani University- Tabriz
4 Department of Civil Engineering-Azarbaijan Shahid Madani University - Tabriz
چکیده [English]

Fine-grained soils with a high percentage of clay minerals are used for covering sanitary landfill and for earth dams' cores because of their low permeability. One of the key factors affecting the behavior of these soils is pore fluid chemistry, so that changes in fluid viscosity and type of cations change the engineering properties of these soils. In this study, the effect of water salinity has been investigated on Atterberg and compaction characteristics, shear strength, pore water pressure of fine-grained soils. For this purpose, Atterberg limits, compaction and undrained triaxial tests were conducted on the fine-grained soils, used in the cores of Shahid Madani and Malekian dams, with different pore fluids. Distilled water, project salty water, NaCl solutions with 0.2, 0.4, and 0.8 molar are used as a pore fluid. The results showed by increasing the salinity of water, the liquid limit, plastic limit and plasticity index decrease in both soils, but these changes are not considerable. The results of the triaxial tests showed increasing NaCl salt concentration does not always increase the shear strength of the soils. The maximum increase in the soil shear strength values in both Malekian and Madani soils was obtained with 0.2 molar which is mentioned as an optimal point. In both soils, by increasing the salinity of water, the excess pore water pressure decreases and there is not any meaningful effect on the deformation modulus secant of soils. The cohesion parameter in both soils are reduced up to 0.4 molar and after that increased by increasing salinity. The saline water with concentration between 0.2 and 0.4 molarraised the internal friction angle of soil and beyond these concentration did not have a positive effect on the friction angle.

کلیدواژه‌ها [English]

  • Fine-grained cohesive soils
  • Atterberg limits
  • Triaxial
  • shear strength
  • salinity

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تحقیقات آب و خاک ایران
دوره 50، شماره 4
شهریور 1398
صفحه 951-963

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