بررسی تأثیر سیمان پرتلند و نانو رس بر پتانسیل فروریزش و شاخص‌های تحکیم خاک فروریزشی

نوع مقاله : مقاله پژوهشی

نویسندگان

1 گروه ژئوتکنیک، دانشکده مهندسی عمران، آب و محیط زیست، دانشگاه شهید بهشتی، پردیس فنی و مهندسی شهید عباسپور، تهران، ایران

2 کارشناسی ارشد مهندسی عمران، ژئوتکنیک، دانشگاه علم و فرهنگ،تهران، ایران

چکیده

فروریزش، کاهش حجم ناگهانی خاک با افزایش رطوبت است که در اثر از بین رفتن مقاومت عوامل پیونددهنده ذرات رخ می‌دهد. خاک‌های فروریزشی در مناطق وسیعی از جهان و در نواحی گرمسیری ایران، یافت می‌شوند. وقوع فروریزش می‌تواند خسارت‌های زیادی به تاسیسات و سازه‌های مجاور خاک تحمیل کند. بنابراین مطالعه رفتار خاک‌های فروریزشی از اهمیت ویژه‌ای برخوردار است. در این تحقیق تثبیت خاک فروریزشی منطقه سرکویر سمنان که از نوع الی با پیوندهای ضعیف رسی است، توسط سیمان پرتلند و نانو رس مورد مطالعه قرار گرفت. سیمان به مقدار 0/5 ،1 و 2/5 و نانو رس به مقدار 0/05 ،0/01و 0/25 درصد وزنی خاک خشک، به خاک فروریزشی اضافه شدند. نمونه‌ها با دانسیته نسبی 14 کیلونیوتون بر متر مکعب و درصد رطوبت 5 ،%آماده شدند. با انجام آزمایش تحکیم بر روی نمونه‌های به‌سازی شده پس از 7 ،14 و 28 روز، شاخص فروریزش مطابق با استاندارد  ASTM D 5333    تعیین شد. نتایج نشان داد که هر دو ماده سیمان و نانو رس می‌توانند پتانسیل فروریزش را کاهش دهند. عملکرد بهسازی بهطور قابل توجهی به مقدار ماده افزودنی و نیز زمان عمل‌آوری وابسته بود. بهترین عملکرد بهسازی در مقادیر پائین نانو رس مشاهده شد و با افزایش مقدار نانو رس، بازده بهسازی کاهش یافت. برخلاف سیمان، فرآیند ً سریع بود و با تبخیر آب درون خاک، تکمیل شد. علاوه بر این، در این تحقیق با تثبیت با نانو رس نسبتا عکس‌برداری میکروسکوپی از نمونه‌های بهسازی شده و بهسازی نشده، رفتار خاک از دیدگاه میکرومکانیک نیز مورد ارزیابی قرار گرفت.

کلیدواژه‌ها

موضوعات


عنوان مقاله [English]

Investigating the effect of Portland cement and Nano-clay on the collapse potential and consolidation indexes of the collapsible soil

نویسندگان [English]

  • Mostafa Zamanian 1
  • Fatemeh Qahremani 2
1 Department of Civil, Water, and Environmental Engineering, Shahid Beheshti University, Tehran, Iran
2 Master of Geotechnical Engineering, University of Science and Culture
چکیده [English]

Collapse refers to a sudden decrease in the soil volume upon wetting which is attributed to a loss in the strength of the inter-particle bonds. Collapsible soils can be founded in vast areas around the word and subtropical areas of Iran. Collapse characteristics contribute to various problems to infrastructures that are constructed on loess soils. For this reason, the collapse behavior of loess soils has been the subject of interest. In this study, stabilization of Semnan loess which is composed of fine sand and silt bonded by weak clay bonds, has been investigated. The loess was mixed with Portland cement in the order of 0.5%, 1%, and 2.5% for and with nano-clay in order of 0.05%, 0.1%, and 0.25%. The specimens were prepared to achieve a dry density of 14 kN/m3 and a water content of 5%. Oedeometer tests were performed to determine the collapse potential according to ASTM D5333 after 7, 14, and 28 days. Results showed that both Portland cement and nano-clay could reduce collapse potential. Improvement performance was significantly dependent on the binder content and curing time. The best improvement performance was observed at low nano-clay content and it was reduced by increasing nano-clay content. Unlike the cement stabilization, treatment process with nano-clay was relatively fast that terminated when soil moisture content was evaporated. In addition, in this study, micromechanical soil behaviors were investigated by scanning electron microscopy (SEM) image of the treated and untreated specimens.

کلیدواژه‌ها [English]

  • Collapsible soil
  • collapse potential
  • Soil improvement
  • Portland cement
  • nano-clay
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