1استادیار و معاون آموزشی دانشکده فنی خوی، دانشگاه ارومیه
2دانشیار، پردیس دانشکده های فنی، دانشکده مهندسی عمران، دانشگاه تهران
چکیده
یک مدل دوفازی برای تحلیل دینامیکی و غیرخطی سازه های خاک مسلح ارائه شده است. مدل مزبور از مدل خمیری تعمیم یافته پاستور-زینکوویچ–چان برای خاک و یک مدل ارتجاعی–خمیری کامل ترسکا برای مسلح کننده بهره می برد. مدل دوفازی توسعه یافته یکی از روشهای همگن سازی است که بر پایه روش کار مجازی بنا نهاده شده است. در مدل دوفازی، توده خاک مسلح از بر هم نهی دو فاز پیوسته ماتریس(خاک) و مسلح کننده(جوشن) تشکیل شده است. مدل خمیری تعمیم یافته ابتدا اصلاح شده و سپس برای رفتار فاز ماتریس به کار گرفته شده است. بین فازها از فرض پیوند کامل استفاده شده است. برای صحت سنجی مدل توسعه داده شده، دو سری دیوار خاک مسلح در مقیاس کوچک تحت بارهای دینامیکی میزلرزه شبیه سازی شده اند. تغییرشکلهای جانبی پیش بینی شده در مدل دوفازی با نتایج آزمونهای میز لرزه مقایسه شدند. بررسی الگوی تغییرشکل و سطوح گسیختگی بالقوه در مدل دوفازی حاکی از مود تغییرشکل واژگونی و تشکیل گوه لغزشی دو خطی است که با نتایج آزمایشگاهی سازگار است.
Introducing a two phase model for nonlinear and dynamic simulation of reinforced soil structures using a modified generalized plasticity model
نویسندگان [English]
Amin Iraji1؛ Orang Farzaneh2
1Assistant professor and faculty deputy, Engineering faculty of Khoy, Urmia University
2Associate professor, School of Civil Engineering, College of Engineering, University of Tehran
چکیده [English]
High flexibility and stability of reinforced soil walls make them very useful structures and cause their extended applications as retaining structures at side embankments of roads, slopes, and as abutments especially at regions with high seismic risk. So, such structures could be recommended for Iran as a country with high seismic risk. Reinforced soil structures may present significant deformations under strong earthquake motions. In this regard, they will not provide expected functionality. Therefore, necessity for extension in application of reinforced soil walls especially high geosynthetic reinforced soil walls and significance of plastic displacement in these structures motivated researchers to give special attention to prediction of reinforced soil walls displacements experimentally and numerically.
Two techniques are available for numerical simulation of the reinforced soil masses. In the first method, the soil and inclusion are considered separately in a layered or discrete analysis. This procedure is very time consuming. The second approach is a homogenization method in which reinforced soil is replaced with an equivalent homogeneous but anisotropic medium. Layer-by-layer modeling is not needed in the homogenization methods, so modifying the arrangement of inclusions is easy. Two-phase model is an extension of classical homogenization methods and was developed in the recent two decays.
This approach is actually a mechanical framework based on the virtual work method. It is a macroscopic description of a composite medium, which is the superposition of individual continuous media (phases). The matrix phase (soil) and reinforcement phase (inclusion) are geometrically coincident at any given point in the multiphase material. The proposed model introduces a two-phase model to simulate the nonlinear dynamic behavior of geosynthetic reinforced soil walls. A modified generalized plasticity model for granular materials was used in the proposed two phase model.
The approach was validated by comparison of the results with those of eight reduced-scale reinforced soil walls subjected to seismic loading in shaking tables. Predicted lateral displacement showed good agreement with the test results. The two phase model predicted critical acceleration amplitudes similar to that observed in the experiments. The predicted potential failure surfaces in the two phase model were consistent with the observed deformation patterns.
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