Modares Civil Engineering journal
مهندسی عمران مدرس
MCEJ
Engineering & Technology
http://mcej.modares.ac.ir
1
admin
2476-6763
10.22034
fa
jalali
1395
3
1
gregorian
2016
6
1
16
2
online
1
fulltext
fa
ظرفیت باربری پی های مسلح شده با ریزشمع
Bearing Capacity of Foundations Reinforced with Micropiles
ریزشمع، یک شمع جایگزینی حفاری و تزریقشده با قطر کمتر از 300 میلیمتر است که عموماً مسلح بوده و برای اجرای آن ابتدا چاه شمع حفاری شده و مسلحکننده در داخل آن قرار میگیرد و سپس ملات به داخل چاه تزریق میشود. از این تکنولوژی برای بهبود ظرفیت باربری پیهای موجود نیز استفاده می شود. تحقیق حاضر به بررسی میزان تاثیر ریزشمع در بهبود ظرفیت باربری پی تحت اثر بارگذاری استاتیکی قائم میپردازد. تعدادی آزمایش بارگذاری بر روی مدل آزمایشگاهی کوچکمقیاس از پی مسلح شده با ریزشمع که بر روی ماسه شل قرار گرفته انجام گردید. برای مسلح نمودن پی صلب دایرهای با قطر 10 سانتیمتر، از ریزشمعهای فولادی آجدار به قطر 6 میلیمتر و طول 20 سانتیمتر استفاده شد. با تغییر زاویه نصب و تعداد ریزشمعها، تاثیر نحوه چیدمان ریزشمعها بر رفتار ژئوتکنیکی پی مطالعه شد. برای سنجش کمّی میزان افزایش ظرفیت باربری پی مسلح شده با ریزشمع، ضریب شبکهای(R) تعریف میشود که عبارتست از نسبت ظرفیت باربری پی مسلح شده با ریزشمع به مجموع ظرفیت باربری پی و ریزشمعها به صورت مجزا. نتایج آزمایش-ها نشان میدهد که مقدار ضریب شبکهای با افزایش تعداد ریزشمعها بالا میرود. همچنین در صورت کاربرد 6 یا 8 ریزشمع، با افزایش زاویه نصب ریزشمع نسبت به امتداد قائم، از مقدار R کاسته میشود. در حالت استفاده از تعداد زیادی ریزشمعهای دارای زاویه نصب کوچک ، ظرفیت باربری به مقدار قابل توجهی افزایش مییابد. مقدار ضریب شبکهای در صورت کاربرد 8 ریزشمع با زاویه نصب 15 درجه، برابر 997/1 میباشد.
Improvement of bearing capacity of existing foundations is of great significance. There exist many methods for practical purposes. Micropile is one of the most promising methods. Micropile is a replacement pile of small diameter (usually less than 300 millimeter) which is frequently reinforced using steel elements. To construct a micropile, steel reinforcement is placed in the borehole after drilling the borehole and subsequently the grout is injected into it. Micropiles transfer the structural loads to the deeper and stronger layers of the ground and confine settlement (similar to conventional pile foundations). They also improve the mechanical properties of soil layer such as density, bearing capacity, permeability and compressibility. Owing to their advantages, micropiles are widely used as foundations of new structures construction and also for reinforcing the foundation of existing structures. This research aims at experimental investigation of bearing capacity of foundations reinforced with micropiles under the condition of static loading. A small-scale physical model of a foundation reinforced with micropiles was developed and a series of static loading tests were carried out on. The model micropile-foundation was located on loose sand. Density of the underlying soil was kept almost uniform throughout the tests. The foundation model was circular and 100 mm and 5o mm in diameter and thickness, respectively. It was made from polyamide and considered to act as a rigid foundation during the loading owing to its material and thickness. This foundation was reinforced with a group of micropiles with 6 mm and 200 mm in diameter and length, respectively. These model micropiles were made from threaded steel bars. In order to mobilize friction, sand grains were glued to the surface of the micropiles. Various arrangements of micropiles including the number and inclination angle of micropiles were tested. From the comparative examination of the observed behavior of micropile foundations, the influence of micropiles’ arrangement on the mechanism and improvement of bearing capacity of foundation was investigated. Number of micropiles used in the group varied from 2 to 8. Micropiles were inclined at different angles (0°, 15°, 13°, 45° and 60°) to study its influence on the behavior of foundation reinforced with these elements. In order to quantitatively assess the degree of improvement in the bearing capacity of surface foundations reinforced with micropiles, an index R called “Network Index” was introduced in this study. The index R of unity means that the bearing capacity of foundations reinforced with micropiles is simply equal to the summation of the individual value of the surface foundation and that of the micropile group. There is an upward trend in the rate of index R when the number of micropiles is increased. On the other hand, in high numbers of micropiles used to reinforce the foundation, index R declines with increasing of inclination angle. In the case of micropiles with low-inclination-angle being implemented, bearing capacity is improved remarkably; an index R of 1.997 is achieved in this study where 8 micropiles inclined at an angle of 15° were used to reinforce the foundation.
پی,ریزشمع,زاویه نصب,تعداد,ضریب شبکهای
Foundation,Micropile,Inclination Angle,Number,Network Index
53
65
http://mcej.modares.ac.ir/browse.php?a_code=A-16-1000-4415&slc_lang=fa&sid=16
Jafar
Bolouri Bazaz
جعفر
بلوری بزاز
100319475328460062542
100319475328460062542
Yes
مشهد میدان آزادی دانشگاه فردوسی مشهد گروه عمران صندوق پستی 1111-91775
Hadis
Jalilian Mashhoud
حدیث
جلیلیان مشهود
100319475328460062541
100319475328460062541
No
دانشگه تربیت مدرس