بررسی ظرفیت باربری نهایی پی مرکب حلقوی پوسته‌ای در خاک دانه ای

نوع مقاله : مقاله پژوهشی

نویسندگان

دانشگاه فردوسی مشهد، دانشکده مهندسی، گروه عمران، مشهد، ایران

چکیده

شکل پی به علت نحوه گسترش تنش در خاک زیر پی و تغییر در مکانیزم گسیختگی خاک، نقش تعیین کننده‌ای در ظرفیت باربری یک سیستم شالوده دارا است. محدودیت منابع جهت گیری طراحی‌ها را به استفاده از روش‌های نوین به منظور بهره‌گیری از حداقل مصالح برای دستیابی به حداکثر کارآیی سوق داده است. هدف این تحقیق مطالعه و بررسی رفتار ژئوتکنیکی پی مرکب حلقوی پوسته‌ای و مقایسه آن با پی‌های حلقوی است. برای رسیدن به این منظور تعدادی آزمایش بر روی پی‌های مرکب حلقوی پوسته‌ای با زوایای پوسته مختلف به صورت مدلسازی آزمایشگاهی در سه حالت ماسه سست، متوسط و متراکم انجام شده است. برای بررسی اثر وجود تیر لبه و همچنین محل قرارگیری آن بر روی ظرفیت باربری پی مرکب، از دو نوع پی با زاویه پوسته 120 درجه با تیر لبه در دو ناحیه محیطی و میانی استفاده شده است. در حین انجام آزمایش‌ها و با کمک ابزار دقیق ، داده‌های بار-نشست به دقت ثبت شده است. نتایج بدست آمده حاکی از آن است که بارنهایی پی‌های مرکب بیشتر از پی حلقوی است و با افزایش زاویه پوسته، مقدار بارنهایی کاهش یافته است. همچنین بازدهی پوسته‌ها در خاک‌های با تراکم کمتر مطلوبتر است. یک رابطه جهت پیش بینی ظرفیت باربری نهایی پی مرکب ارائه شده است. با افزودن تیر محیطی به پی مرکب ضمن رفتار بهتر این پی‌ها در نشست‌های لحظه گسیختگی، افزایش بازدهی پوسته در همه تراکم‌ها نسبت به پی مرکب فاقد تیر محیطی مشاهده شده است. بنابراین وجود پوسته و تیر لبه در پی حلقوی باعث بهبود و تقویت ظرفیت باربری نهایی می‌گردد.

کلیدواژه‌ها

موضوعات


عنوان مقاله [English]

Ultimate Bearing Capacity of Composite Shell Annular Foundations in Cohesionless Soil

نویسندگان [English]

  • M. KAZEMI
  • J. Bolouri Bazaz
Civil Engineering Department, Ferdowsi University of Mashhad, Mashhad, Iran
چکیده [English]

The foundation shape effects on the stress distribution induced in the soil. Moreover, it has influence on the failure mechanism of the soil. For these reasons, it plays an important role in the ultimate bearing capacity of the foundation. Due to lack of materials, the new design methods attempt to utilize the least amount of material and achieve the maximum efficiency. If shell elements are employed in composite foundations, and the interaction effects are considered, the cost can be reduced. This paper aims to compare the geotechnical performance of the composite annular shell foundation with that of the annular one. For this purpose, the ultimate bearing capacity and the settlement of these foundations are experimentally modeled for various shell angles. The findings prove that the ultimate bearing capacity of the composite foundations is more than that of the annular one. Furthermore, it is observed that increasing the shell angle reduces the ultimate bearing capacity. Moreover, the shell efficiency factor is decreased by increasing the soil relative density. This phenomenon shows that the shells perform more appropriately in low-density soils. Additionally, a novel relation is proposed for predicting the ultimate bearing capacity of the composite shell. It is worth emphasizing that adding the edge beam to composite foundations improves its performance in settlements during failure. Moreover, the efficiency of foundations with edge beams is more than the ones without beam in soils with any density. Hence, using of shells in annular foundation enhances its ultimate bearing capacity.

کلیدواژه‌ها [English]

  • Ultimate Bearing Capacity
  • Composite foundation
  • Shell foundation
  • Annular foundation
  • Sand
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