نشست پی‌های نواری واقع بر خاک ماسه‌ای تحت اثر بارگذاری سیکلی

نوع مقاله : مقاله پژوهشی

نویسندگان

1 دانشکده مهندسی عمران، واحد سمنان، دانشگاه آزاد اسلامی، سمنان، ایران

2 دانشکده مهندسی عمران و محیط زیست، دانشگاه صنعتی امیرکبیر، تهران، ایران

3 دانشکده مهندسی، دانشگاه فردوسی مشهد، مشهد، ایران

چکیده

موارد بسیاری وجود دارد که پی سازه­ علاوه بر بار استاتیکی، در معرض بارگذاری سیکلی قرار می­ گیرد که از آن جمله می ­توان به زلزله، بار ناشی از ترافیک و ارتعاش ناشی از ماشین­ آلات اشاره نمود. در این مطالعه آزمایشگاهی، تأثیر عرض پی، تراکم خاک ماسه ­ای، تعداد سیکل بارگذاری، شدت سربارهای استاتیکی و سیکلی بر نشست سیکلی پی نواری مورد بررسی قرار گرفته است. مصالح خاکی مورد استفاده در این تحقیق، ماسه متوسط بد دانه­ بندی شده (SP) است. مدل پی دارای عرض 5، 7/5 و 10 سانتی­ متر و طول آن، 34 سانتی ­متر است. سیستم بارگذاری به‌ صورت هوای فشرده است که قابلیت اعمال بار یکنواخت و سیکلی را دارا است. در خاک ماسه ­ای با تراکم متوسط و متراکم، مقدار متوسط نشست پی در سیکل اول بارگذاری، به ترتیب حدود 46 و 51 درصد کل نشست سیکلی است. خاک ماسه‌ای با تراکم متوسط زیر پی، در نشستی معادل 22 تا 27 درصد عرض پی دچار گسیختگی شده است. خاک ماسه‌ای متراکم زیر پی، در نشستی معادل 33 تا 43 درصد عرض پی دچار گسیختگی شده است. هر چه سربار کل وارد به خاک کمتر باشد، خاک تعداد سیکل بارگذاری بیشتری را تحمل می­ کند تا دچار گسیختگی شود؛ یعنی با ازدیاد سربار استاتیکی و سیکلی، خاک در تعداد سیکل کمتری دچار گسیختگی شده است. با توجه به ایجاد نشست ماندگار در پی تحت اثر بارهای سیکلی، در طراحی پی‌ها تحت اثر این نوع بار، مقدار نشست پیش‌بینی ‌شده حتماً بایستی از مقدار مجاز آن کمتر باشد.

کلیدواژه‌ها

موضوعات


عنوان مقاله [English]

Settlement of Strip Footings on Sand Subjected to Cyclic Loading

نویسندگان [English]

  • Mahmoud Nikkhah 1
  • Seyed Majdeddin Mir Mohammad Hosseini 2
  • Saeed Abrishami 3
1 Department of Civil Engineering, Semnan Branch, Islamic Azad University, Semnan, Iran
2 Department of Civil and Environmental Engineering, Amirkabir University, Tehran, Iran
3 Department of Civil Engineering, Ferdousi University, Mashhad, Iran
چکیده [English]

There are many cases in which the foundation, in addition to static load, is exposed to cyclic loading, such as earthquakes, traffic loads, and machine vibrations. In this laboratory study, the effect of foundation width, sandy soil density, number of loading cycles, static and cyclic overhead intensity on cyclic strip foundation settlement has been investigated. The soil material used in this research is poorly graded medium sand (SP). The foundation model has a width of 5, 7.5 and 10 cm and its length is 34 cm. In medium and dense sandy soils, the average amount of foundation settlement in the first loading cycle is about 46 and 51% of the total cyclic settlement, respectively. Medium-density sandy soils below the foundation have failed at a settlement of 22 to 27% of the foundation width. The dense sandy soil beneath the foundation has failed at a settlement of 33 to 43% of the width of the foundation. The lower the total overhead entering the soil, the more loading cycles the soil can withstand to fail; That is, with increasing static and cyclic overhead, the soil is failed in a smaller number of cycles. Due to the creation of permanent settlements under the effect of cyclic loads, in the design of foundations under the effect of this type of load, the amount of predicted settlement must be less than the allowable amount.

کلیدواژه‌ها [English]

  • Sand density
  • foundation width
  • settlement
  • static overhead
  • cyclic overhead
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