اثر چیدمان شمع بر عملکرد پی-شمع

شمع‌ها ضمن مشارکت در باربری پی شمع، نشست را به طور قابل ملاحظه‌ای کاهش می‌دهند. در این پژوهش با مدلسازی سه‌بعدی پی شمع‌ها در نرم‌افزار اجزا محدود plaxis 3d foundation در دو نوع خاک رس متوسط و ماسه‌ متراکم، تاثیر چیدمان شمع‌ها و شکل رادیه بر عملکرد مجموعه پی مطالعه شد. نتایج مدل‌ها مشخص کرد که در دو پی همجوار و متقارن در ماسه که تحت بارگذاری یکنواخت هستند با انتقال شمع‌های گوشه‌ای و جایگذاری شمع‌های بلندتر در نزدیکی محور تقارن بین آنها، می‌توان نشست و دوران پی را بیش از 50 درصد کاهش داد. همچنین برای پی‌های مربعی با نشست کلی 154 میلی‌متر در دو نوع خاک رسی و ماسه‌ای، اثر چیدمان‌های مختلف شمع بررسی شد. بر اساس نتایج عددی، در خاک رسی با چینش شمع‌های بلندتر در مرکز پی و در خاک ماسه‌ای با تمرکز شمع‌ها در هسته مرکزی پی، بیش‌ترین کاهش نشست حاصل می‌شود. در مدل‌ها حجم شمع‌ها باهم مساوی است.

Effect of Piles Arrangement on the Performance of Piled Raft Foundations

Summary Piledraft foundation is a complex system that divide the overall load between the piles and raft upon pilesoilraft interaction. Piles mainly act as a settlement reducer. Piledraft foundations with different piles arrangement and soil type, i.e. medium clay and dense sand, were modeled in 3D finite element software, PLAXIS 3D Foundation. Influence of piles on differential settlement depends on the piles arrangement and soil properties. The numerical results showed that in two adjacent and symmetrical foundations on sand under uniform surcharge, when corner piles were removed and longer piles were placed close to the symmetry axes of the foundations, the foundation settlement and rotation decreased considerably (at least 50%). For piledraft foundation on soft with placement of longer piles in the center raft and shorter piles out of center, the optimal piles arrangement was achieved, while in dense sand piles concentration in the central region of raft was optimal arrangement. These later results obtained from rafts on clay and sand with different surcharge that has been analyzed to attain equal 154mm settlement.   Introduction One of the effective ways to improve the footing bearing capacity is using pile foundations. The piledraft foundation is a new design concept as one of the effective methods of foundation to reduce settlements of structures.  In piled raft foundation role of raft foundation is to provide adequate bearing capacity and role of pile foundation is mainly to act as settlement reducers. In this paper 3D finite element analysis of piled raft foundations on dense sand and medium clay was studied. The purpose of the present study is to investigate the role of piles arrangement in reducing settlement of the piled raft foundation.   Methodology and Approaches Numerical method used for analysis of piled raft foundation, due to complex soilstructure interaction. A 3D finite element software, PLAXIS 3D Foundation utilized to analyze three dimensional models of piled raft foundation. The model results validated among settlements of Messe–Torhaus structure in Germany which was modeled in ABAQUS. Different pile arrangement plan in dense sand and medium clay was molded. Soil behavior was modeled by MohrCoulomb elastoplastic model.   Results and Conclusions Piles arrangement has a significant influence on the performance of piled raft foundation. Numerical results show that appropriate arrangement of piles which has maximum reduction in settlement strongly depends on soil type. Additionally, increasing the piles length has more influence on the performance of piled raft foundation, rather than pile diameter growth, when the volume of concrete in piles bodies has been constant.