بررسی رفتار مهندسی خاک‌های مارنی تحت تأثیر رژیم‌های حرارتی و pH‌های متفاوت از منظر ریز ساختاری

نوع مقاله : مقاله پژوهشی

نویسندگان

1 گروه مهندسی عمران، دانشگاه هرمزگان، بندرعباس، ایران،

2 گروه مهندسی عمران، دانشگاه هرمزگان، بندرعباس، ایران

چکیده

استفاده از خاک‌‌های رسی به‌عنوان پوشش محافظ در دفن زباله‌های سطح بالا از جمله مواردی است که رس تحت رژیم‌های حرارتی متوسط تا زیاد قرار می‌گیرد. مارن‌‌ها از جمله نهشته‌‌های رسوبی هستند که از کانی‌‌های رسی و کربنات کلسیم تشکیل شده‌‌اند. مجاورت خاک با آلودگی ناشی از مراکز دفن زباله موجب تغییر pH آن می‌شود. از سوی دیگر به دلیل پتانسیل تولید حرارت توسط زباله‌های سطح بالا، پوشش رسی مورد استفاده در معرض رژیم‌های حرارتی مختلف قرار می‌گیرد که منجر به تغییر مشخصات فیزیکی، مکانیکی و ریزساختاری آن‌ می‌شود. بر این اساس هدف این مقاله بررسی تأثیر همزمان تغییرات pH و رژیم‌های حرارتی در مراکز دفن زباله سطح بالا است. در پژوهش حاضر تأثیر توأم pH و حرارت بر رفتار خاک مارن با استفاده از آزمایش‌های مقاومت فشاری محدود نشده، افت وزنی و حدود اتربرگ، تعیین مقدار کربنات توسط تیتراسیون، پراش اشعه ایکس (XRD) و تصاویر میکروسکوپ الکترونی روبشی (SEM) مورد ارزیابی قرار گرفته است. بدین منظور جهت تغییر pH از محلول اسید کلریک (HCl) و محلول سدیم هیدروکسید (NaOH) استفاده شده است. بعد از ثابت شدن pH خاک مارن در مقادیر4، 6، 8، 11 و 13 نمونه‌ها در گرمخانه خشک شده، سپس به مدت 2 ساعت در معرض سطوح حرارتی 25، 100، 300، 500، 700 و 900 درجه سلسیوس قرار گرفته است. از مهم‌ترین نتایج این پژوهش خارج شدن کربنات در شرایط اسیدی و تغییرات برجسته خصوصیات مهندسی خاک مارن در محدوده حرارتی°C500 تا °C900 است. کانی پالیگورسکایت در محیط اسیدی و قلیایی پایدار و در دمای°C700 با وقوع دی‌هیدروکسیلاسیون تخریب می‌شود. از طرفی حذف کربنات در محیط اسیدی منجر به افزایش خواص خمیری و تغییر طبقه‌بندی خاک مارن از رس با دامنه خمیری کم (CL) به رس با دامنه خمیری زیاد (CH) شده است. با کاهش pH و افزایش دما، مقاومت فشاری افزایش یافته است، به نحوی که در 4= pH مقاومت فشاری به MPa 0/3 افزایش یافته است. از سوی دیگر در دمای °C 700 مقاومت فشاری خاک مارن طبیعی به 10/96 افزایش یافته است.

کلیدواژه‌ها

موضوعات

عنوان مقاله [English]

Investigating the engineering behavior of marl soils under the influence of thermal regimes and different pHs from a microstructural perspective

نویسندگان [English]

  • Mohammad Amiri 1
  • Masoud Dehghani 2
  • Omid Jafar 2
1 Faculty of Civil Engineering, University of Hormozgan, Hormozgan, Iran
2 Faculty of Civil Engineering, University of Hormozgan, Hormozgan, Iran
چکیده [English]

Proximity of soil with pollution caused by landfills changes its pH. On the other hand, due to the heat generation potential of high-level waste, the used clay coating is exposed to different thermal regimes, which leads to changes in its physical, mechanical, and microstructural characteristics. Based on this, This article aims to investigate the simultaneous effect of pH changes and thermal regimes in high-level waste disposal centers. In this study, the combined effect of pH and temperature on the behavior of marl soil was evaluated using unconfined compressive strength tests, weight loss, and Atterberg limits, determination of carbonate amount by titration, X-ray diffraction (XRD) and scanning electron microscope (SEM) images. For this purpose, hydrochloric acid (HCl) and sodium hydroxide (NaOH) solutions have been used to change the pH. After the pH of the marl soil was fixed at 4, 6, 8.3, 11, and 13, the samples were dried in the oven, then exposed to the thermal levels of 25, 100, 300, 500, 700, and 900 degrees Celsius for 2 hours. One of the most important results of this research is the removal of carbonate in acidic conditions and prominent changes in the engineering characteristics of marl soil in the thermal range of 500 ℃ to 900 ℃. Palygorskite mineral is destroyed in the stable acidic and alkaline environment at 700 ℃ with the occurrence of dihydroxylation. On the other hand, the removal of carbonate in an acidic environment has led to an increase in plasticity properties and a change in the classification of marl soil. As the pH decreases and the temperature increases, the compressive strength increases.

کلیدواژه‌ها [English]

  • Marl soil
  • pH
  • Thermal stabilization
  • unconfined compressive strength
  • SEM & XRD microstructural studies

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نشریه مهندسی عمران امیرکبیر
دوره 56، شماره 3
1403
صفحه 279-300

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