بررسی آزمایشگاهی و تحلیلی رفتار پی رادیه شمع متصل و غیرمتصل

نوع مقاله : مقاله پژوهشی

نویسندگان

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

2 دانشگاه فردوسی مشهد دانشکده مهندسی گروه مهندسی عمران

چکیده

در پی رادیه شمع برخلاف گروه شمع، پی و شمع­‌ها هم‌زمان در انتقال بار به خاک نقش بازی می­‌کنند. تمرکز تنش برشی و لنگر خمشی در محل اتصال شمع به پی در پی رادیه شمع می­تواند موجب گسیختگی سازه‌­ای گردد حال ‌آن که هنوز ظرفیت باربری ژئوتکنیکی شمع‌­ها کاملاً بسیج نشده است. این مشکل می­‌تواند با جداسازی شمع­‌ها از پی و قرار دادن یک ‌لایه­ خاک بین سر شمع‌ها و کف پی و استفاده از پی رادیه شمع غیرمتصل مرتفع شود. این لایه خاک در پی­‌های رادیه شمع غیرمتصل لایه میانی نامیده می­‌شود. در پی رادیه شمع غیرمتصل لایه میانی نقش مهمی در بسیج کردن ظرفیت باربری خاک بستر، تنظیم مکانیزم انتقال بار و تغییر سختی کل سیستم بازی می­‌کند. به دلیل رفتار بسیار پیچیده پی رادیه شمع متصل و غیرمتصل، تخمین سختی و نسبت تقسیم بار در این سیستم­‌ها برای طراحی اولیه مشکل می‌­باشد. در پژوهش حاضر، روشی تحلیلی جهت محاسبه سهم باربری شمع‌­ها از کل بار وارده و سختی در پی رادیه شمع متصل و غیرمتصل بر اساس نتایج آزمایش بر روی پی سطحی و گروه شمع ارائه‌ شده است. این مدل با انجام 21 آزمایش بر روی پی بدون شمع، گروه شمع، پی رادیه شمع غیرمتصل و متصل مورد صحت سنجی قرار گرفته است. با توجه به نتایج به ‌دست ‌آمده، افزایش تعداد و طول شمع­ها موجب بهبود ظرفیت باربری می­گردد؛ در پی رادیه شمع غیرمتصل با افزایش ضخامت لایه میانی سهم باربری شمع­‌ها، سختی و ظرفیت باربری سیستم کاهش می­‌یابد.

کلیدواژه‌ها

موضوعات

عنوان مقاله [English]

Experimental and Analytical Study of connected and non-connected piled raft foundations

نویسنده [English]

  • Mohammad Jamal Malekkhani 1
1 Civil Engineering Department, Ferdowsi University of Mashhad, Mashhad, Iran
چکیده [English]

In the piled raft foundation, in contrast to the pile group, both raft and piles transfer the imposed load to the foundation soil. The concentration of shear stresses and bending moments at the connection point of the pile and raft in the piled raft may cause a structural collapse in the pile while the geotechnical bearing capacity of the pile has not fully mobilized. This problem may be solved by disconnecting the piles from raft and inserting a soil layer between the piles and the raft. This layer in non-connected piled rafts is called cushion. In a non-connected piled raft, the cushion plays an important role to mobilize the bearing capacity of the foundation soil, adjusting the load transfer mechanism, and changing the system stiffness. The behavior of a connected and non-connected piled raft is too complicated to easily estimate the load sharing ratio and stiffness for the preliminary design. In the present research, based on the test results of the pile group and the unpiled raft, an analytical approach is introduced to calculate the load sharing ratio and the stiffness of the connected and non-connected piled rafts. To verify the proposed analytical model accuracy, 21 small scale tests on the unpiled raft, pile group, connected and non-connected piled rafts were conducted. According to the results increasing the number and length of piles, increases the bearing capacity. In a non-connected piled raft, increasing the cushion thickness decreases the load sharing ratio of piles, stiffness, and bearing capacity of the system.

کلیدواژه‌ها [English]

  • Piled raft foundation
  • Pile group
  • Analytical approach
  • Stiffness
  • Load sharing ratio

مراجع

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نشریه مهندسی عمران امیرکبیر
دوره 53، شماره 12
اسفند 1400
صفحه 5195-5218

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