دانشگاه صنعتی امیرکبیر نشریه مهندسی عمران امیرکبیر 2588-297X 50 4 2018 10 23 Ultimate Bearing Capacity of Composite Shell Annular Foundations in Cohesionless Soil بررسی ظرفیت باربری نهایی پی مرکب حلقوی پوسته‌ای در خاک دانه ای 781 792 1039 10.22060/ceej.2017.12628.5235 FA مجید کاظمی دانشگاه فردوسی مشهد، دانشکده مهندسی، گروه عمران، مشهد، ایران جعفر بلوری بزاز دانشگاه فردوسی مشهد، دانشکده مهندسی، گروه عمران، مشهد، ایران Journal Article 2017 03 07 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. <span lang="AR-SA" dir="RTL">شکل</span><span lang="AR-SA"> <span dir="RTL">پی</span> <span dir="RTL">به</span> <span dir="RTL">علت</span> <span dir="RTL">نحوه</span> <span dir="RTL">گسترش</span> <span dir="RTL">تنش</span> <span dir="RTL">در</span> <span dir="RTL">خاک</span> <span dir="RTL">زیر</span> <span dir="RTL">پی</span> <span dir="RTL">و</span> <span dir="RTL">تغییر</span> <span dir="RTL">در</span> <span dir="RTL">مکانیزم</span> <span dir="RTL">گسیختگی</span> <span dir="RTL">خاک،</span> <span dir="RTL">نقش</span> <span dir="RTL">تعیین کننده‌ای</span> <span dir="RTL">در</span> <span dir="RTL">ظرفیت</span> <span dir="RTL">باربری</span> <span dir="RTL">یک</span> <span dir="RTL">سیستم</span> <span dir="RTL">شالوده</span> <span dir="RTL">دارا</span> <span dir="RTL">است</span></span><span>. <span lang="AR-SA" dir="RTL">محدودیت</span><span lang="AR-SA"> <span dir="RTL">منابع</span> <span dir="RTL">جهت گیری</span> <span dir="RTL">طراحی‌ها</span> <span dir="RTL">را</span> <span dir="RTL">به</span> <span dir="RTL">استفاده</span> <span dir="RTL">از</span> <span dir="RTL">روش‌های</span> <span dir="RTL">نوین</span> <span dir="RTL">به</span> <span dir="RTL">منظور بهره‌گیری</span> <span dir="RTL">از</span> <span dir="RTL">حداقل</span> <span dir="RTL">مصالح</span> <span dir="RTL">برای</span> <span dir="RTL">دستیابی</span> <span dir="RTL">به</span> <span dir="RTL">حداکثر</span> <span dir="RTL">کارآیی</span> <span dir="RTL">سوق</span> <span dir="RTL">داده</span> <span dir="RTL">است</span></span>. <span lang="AR-SA" dir="RTL">هدف</span><span lang="AR-SA"> <span dir="RTL">این</span> <span dir="RTL">تحقیق</span> <span dir="RTL">مطالعه</span> <span dir="RTL">و</span> <span dir="RTL">بررسی</span> <span dir="RTL">رفتار</span> <span dir="RTL">ژئوتکنیکی پی</span> <span dir="RTL">مرکب</span> <span dir="RTL">حلقوی</span> <span dir="RTL">پوسته‌ای</span> <span dir="RTL">و</span> <span dir="RTL">مقایسه</span> <span dir="RTL">آن</span> <span dir="RTL">با</span> <span dir="RTL">پی‌های</span> <span dir="RTL">حلقوی</span> <span dir="RTL">است</span></span>. <span lang="AR-SA" dir="RTL">برای</span><span lang="AR-SA"> <span dir="RTL">رسیدن</span> <span dir="RTL">به</span> <span dir="RTL">این</span> <span dir="RTL">منظور</span> <span dir="RTL">تعدادی</span> <span dir="RTL">آزمایش</span> <span dir="RTL">بر</span> <span dir="RTL">روی</span> <span dir="RTL">پی‌های مرکب</span> <span dir="RTL">حلقوی</span> <span dir="RTL">پوسته‌ای</span> <span dir="RTL">با</span> <span dir="RTL">زوایای</span> <span dir="RTL">پوسته</span> <span dir="RTL">مختلف</span> <span dir="RTL">به</span> <span dir="RTL">صورت</span> <span dir="RTL">مدلسازی</span> <span dir="RTL">آزمایشگاهی</span> <span dir="RTL">در</span> <span dir="RTL">سه</span> <span dir="RTL">حالت</span> <span dir="RTL">ماسه</span> <span dir="RTL">سست،</span> <span dir="RTL">متوسط</span> <span dir="RTL">و</span> <span dir="RTL">متراکم انجام</span> <span dir="RTL">شده</span> <span dir="RTL">است</span></span>. <span lang="AR-SA" dir="RTL">برای</span><span lang="AR-SA"> <span dir="RTL">بررسی</span> <span dir="RTL">اثر</span> <span dir="RTL">وجود</span> <span dir="RTL">تیر</span> <span dir="RTL">لبه</span> <span dir="RTL">و</span> <span dir="RTL">همچنین</span> <span dir="RTL">محل</span> <span dir="RTL">قرارگیری</span> <span dir="RTL">آن</span> <span dir="RTL">بر</span> <span dir="RTL">روی</span> <span dir="RTL">ظرفیت</span> <span dir="RTL">باربری</span> <span dir="RTL">پی</span> <span dir="RTL">مرکب،</span> <span dir="RTL">از</span> <span dir="RTL">دو</span> <span dir="RTL">نوع</span> <span dir="RTL">پی با</span> <span dir="RTL">زاویه</span> <span dir="RTL">پوسته</span> <span dir="RTL">120</span> <span dir="RTL">درجه</span> <span dir="RTL">با</span> <span dir="RTL">تیر</span> <span dir="RTL">لبه</span> <span dir="RTL">در</span> <span dir="RTL">دو</span> <span dir="RTL">ناحیه</span> <span dir="RTL">محیطی</span> <span dir="RTL">و</span> <span dir="RTL">میانی</span> <span dir="RTL">استفاده</span> <span dir="RTL">شده</span> <span dir="RTL">است</span></span>. <span lang="AR-SA" dir="RTL">در</span><span lang="AR-SA"> <span dir="RTL">حین</span> <span dir="RTL">انجام</span> <span dir="RTL">آزمایش‌ها</span> <span dir="RTL">و</span> <span dir="RTL">با</span> <span dir="RTL">کمک</span> <span dir="RTL">ابزار دقیق</span> <span dir="RTL">،</span> <span dir="RTL">داده‌های</span> <span dir="RTL">بار</span></span>-<span lang="AR-SA" dir="RTL">نشست</span><span lang="AR-SA"> <span dir="RTL">به</span> <span dir="RTL">دقت</span> <span dir="RTL">ثبت</span> <span dir="RTL">شده</span> <span dir="RTL">است</span></span>. <span lang="AR-SA" dir="RTL">نتایج</span><span lang="AR-SA"> <span dir="RTL">بدست</span> <span dir="RTL">آمده</span> <span dir="RTL">حاکی</span> <span dir="RTL">از</span> <span dir="RTL">آن</span> <span dir="RTL">است</span> <span dir="RTL">که</span> <span dir="RTL">بارنهایی</span> <span dir="RTL">پی‌های</span> <span dir="RTL">مرکب</span> <span dir="RTL">بیشتر</span> <span dir="RTL">از</span> <span dir="RTL">پی حلقوی</span> <span dir="RTL">است</span> <span dir="RTL">و</span> <span dir="RTL">با</span> <span dir="RTL">افزایش</span> <span dir="RTL">زاویه</span> <span dir="RTL">پوسته،</span> <span dir="RTL">مقدار</span> <span dir="RTL">بارنهایی</span> <span dir="RTL">کاهش</span> <span dir="RTL">یافته</span> <span dir="RTL">است</span></span>. <span lang="AR-SA" dir="RTL">همچنین</span><span lang="AR-SA"> <span dir="RTL">بازدهی</span> <span dir="RTL">پوسته‌ها</span> <span dir="RTL">در</span> <span dir="RTL">خاک‌های</span> <span dir="RTL">با</span> <span dir="RTL">تراکم</span> <span dir="RTL">کمتر مطلوبتر</span> <span dir="RTL">است</span></span>. <span lang="AR-SA" dir="RTL">یک</span><span lang="AR-SA"> <span dir="RTL">رابطه</span> <span dir="RTL">جهت</span> <span dir="RTL">پیش بینی</span> <span dir="RTL">ظرفیت</span> <span dir="RTL">باربری</span> <span dir="RTL">نهایی</span> <span dir="RTL">پی</span> <span dir="RTL">مرکب</span> <span dir="RTL">ارائه</span> <span dir="RTL">شده</span> <span dir="RTL">است</span></span>. <span lang="AR-SA" dir="RTL">با</span><span lang="AR-SA"> <span dir="RTL">افزودن</span> <span dir="RTL">تیر</span> <span dir="RTL">محیطی</span> <span dir="RTL">به</span> <span dir="RTL">پی</span> <span dir="RTL">مرکب ضمن</span> <span dir="RTL">رفتار</span> <span dir="RTL">بهتر</span> <span dir="RTL">این</span> <span dir="RTL">پی‌ها</span> <span dir="RTL">در</span> <span dir="RTL">نشست‌های</span> <span dir="RTL">لحظه</span> <span dir="RTL">گسیختگی،</span> <span dir="RTL">افزایش</span> <span dir="RTL">بازدهی</span> <span dir="RTL">پوسته</span> <span dir="RTL">در</span> <span dir="RTL">همه</span> <span dir="RTL">تراکم‌ها</span> <span dir="RTL">نسبت</span> <span dir="RTL">به</span> <span dir="RTL">پی</span> <span dir="RTL">مرکب</span> <span dir="RTL">فاقد تیر</span> <span dir="RTL">محیطی</span> <span dir="RTL">مشاهده</span> <span dir="RTL">شده</span> <span dir="RTL">است</span></span>. <span lang="AR-SA" dir="RTL">بنابراین</span><span lang="AR-SA"> <span dir="RTL">وجود</span> <span dir="RTL">پوسته</span> <span dir="RTL">و</span> <span dir="RTL">تیر</span> <span dir="RTL">لبه</span> <span dir="RTL">در</span> <span dir="RTL">پی</span> <span dir="RTL">حلقوی</span> <span dir="RTL">باعث</span> <span dir="RTL">بهبود</span> <span dir="RTL">و</span> <span dir="RTL">تقویت</span> <span dir="RTL">ظرفیت</span> <span dir="RTL">باربری</span> <span dir="RTL">نهایی</span> <span dir="RTL">می‌گردد.</span></span></span> https://ceej.aut.ac.ir/article_1039_27ed0fb950b856b06e1273989422e7d3.pdf