بررسی و مقایسه ویژگی‌های مقاومتی خاک‌های ماسه‌ای با تغییر درصد رطوبت و مشخصات بخش ریزدانه

نوع مقاله : مقاله پژوهشی

نویسندگان

گروه مهندسی عمران- دانشکده فنی و مهندسی-دانشگاه قم- قم- ایران

چکیده

در طبیعت، خاک ماسه‌ای به ندرت به شکل تمیز و خالص می‌باشد و اغلب دارای مقادیر مختلفی ریزدانه است. انتظار می‌رود که حضور ریزدانه در خاک ماسه‌ای عملکرد مقاومت برشی و اتساعی خاک ماسه را تحت تأثیر قرار دهد؛ لذا در تحقیق حاضر با یک ایده جدید در ساخت نمونه ها، رفتار مقاومتی و اتساعی مخلوط ماسه ترکیب شده با ریزدانه با استفاده از دستگاه برش مستقیم کوچک مقیاس با دو نوع ریزدانه سیلت و رس و در چهار درصد ریزدانه متفاوت 10، 20، 30 و 40 و در سه تراکم نسبی 30، 60 و 90 درصد و با دو درصد رطوبت بهینه و اشباع، آماده و تحت تنشهای قائم 0.5، 1 و 1.5 کیلوگرم بر سانتیمتر مربع مورد بررسی قرار گرفتند. نتایج این تحقیق نشان می‌دهد که افزایش مقدار ریزدانه منجر به کاهش مقاومت برشی خاک ماسه‌ای می‌گردد و ریزدانه رسی مقاومت برشی خاک ماسه را بیشتر کاهش می‌دهد. همچنین افزایش درصد ریزدانه چه از نوع سیلت و چه از نوع رس سبب کاهش اتساع و زاویه اتساع و همچنین زاویه اصطکاک داخلی خاک ماسه‌ای می‌گردد؛ البته رس نسبت به سیلت پارامترهای مذکور را بیشتر کاهش داده است. پارامتر چسبندگی نیز با افزایش ریزدانه افزایش می‌یابد و البته در مخلوط رسی پارامتر چسبندگی با افزایش رس، بیشتر افزایش یافته است. همچنین نرخ تغییرات پارامتر چسبندگی با افزایش درصد ریزدانه افزایش می‌یابد.

کلیدواژه‌ها


عنوان مقاله [English]

Investigating and comparing the resistance characteristics of sandy soils with changing the percentage of moisture and fine-grained characteristics

نویسندگان [English]

  • Mahdi Khodaparast
  • marzie yousefali
  • Fatemeh Vahidi-Nia
Department of Civil Engineering, Faculty of Engineering, University of Qom, Qom, Iran
چکیده [English]

In nature, sandy soils are rarely clean and often contain some clay and silt. These fines grain have a significant effect on the resistance and dilation behavior of sandy soils. Therefore, in this study, resistance and dilation behavior of sand mixture with fine grains such as silt and clay using a small scale direct shear test have been studied. Tests are conducted on specimens of sand with various fine content ranging from 0 to 40%, density of 30, 60 and 90 percent and the samples are subjected to three normal stresses 0.5, 1.0 and 1.5 kg/cm2 with two percent of optimum and saturation moisture. The test results show with increase in percentage of fine grains, the shear strength of sandy soil decrease and with increase in percentage of clay the shear strength decreases further. Also, dilation angle and angle of friction decreases with increase fine grains content and cohesion parameter increases with increase fine grains, Of course, it more increases with increase clay content and the rate of change of the cohesion parameter increases with increasing fine-grained percentage.

کلیدواژه‌ها [English]

  • Direct shear test
  • Clay and silt
  • Shear strength
  • Internal friction angle
  • dilation
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