معرفي يك مدل دو فازي براي تحليل ديناميكي غيرخطي سازه هاي خاك مسلح با استفاده از نظريه ي خميري تعميم يافته ي اصلاح شده

INTRODUCING A TWO PHASE MODEL FOR NONLINEAR an‎d DYNAMIC SIMULATION OF REINFORCED SOIL STRUCTURES USING A MODIFIED GENERALIZED PLASTICITY MODEL

در پژوهش حاضر، يك مدل دوفازي براي تحليل ديناميكي و غيرخطي سازه هاي خاك مسلح ارايه شده است، كه از مدل خميري تعميم يافته ي پاستور زينكوويچ چان براي خاك و يك مدل ارتجاعي خميري كامل ترسكا براي مسلح كننده بهره مي برد. مدل دوفازي توسعه يافته، يكي از روش هاي همگن سازي است، كه بر پايه ي روش كار مجازي بنا نهاده شده است. در مدل دوفازي، توده ي خاك مسلح از بر هم نهي دو فاز پيوسته ي ماتريس (خاك) و مسلح كننده (جوشن) تشكيل شده است. مدل خميري تعميم يافته، ابتدا اصلاح و سپس براي رفتار فاز ماتريس استفاده شده است. بين فازها از فرض پيوند كامل استفاده شده است. براي صحت سنجي مدل توسعه داده شده، تعداد دو سري ديوار خاك مسلح در مقياس كوچك تحت بارهاي ديناميكي ميزلرزه شبيه سازي شده اند. تغيير شكل هاي جانبي و ماندگار پيش بيني شده در مدل دوفازي با نتايج آزمون هاي ميزلرزه مقايسه شدند. بررسي الگوي تغيير شكل و سطوح گسيختگي بالقوه در مدل دوفازي، حاكي از مود تغيير شكل واژگوني و تشكيل گوه ي لغزشي دو خطي در ديوار خاك مسلح است، كه با نتايج آزمايشگاهي سازگار است.

High exibility and stability of reinforced soil walls make them very useful structures and cause their extended applications as retaining structures at side embankments of roads and slopes and as abutments, especially in regions with high seismic risk. Therefore, such structures could be recommended for Iran as a country with high seismic risk. Reinforced soil structures may present signi cant deformations under strong earthquake motions. In this regard, they will not provide expected functionality. Therefore, the necessity of extension in the application of reinforced soil walls, especially high geosynthetic reinforced soil walls, and the signicance of plastic displacement in these structures motivated researchers to give special attention to the prediction of reinforced soil walls' displacements experimentally and numerically. Two techniques are available for the numerical simulation of the reinforced soil masses. In the rst 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 by which reinforced soil is replaced with an equivalent homogeneous, yet anisotropic, medium. Layer-by-layer modeling is not needed in the homogenization methods; therefore, the modication of the arrangement of inclusions is easy. The two-phase model is the extension of classical homogenization methods and has developed in the recent two decades. 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 modied generalized plasticity model for granular materials was used in the proposed two-phase model. The approach was validated by the comparison of the results and those of eight reducedscale reinforced soil walls subjected to seismic loading in shaking tables. The predicted lateral displacement showed good agreement with the test results. The twophase model predicted critical acceleration amplitudes similar to those observed in the experiments. The predicted potential failure surfaces in the two-phase model were consistent with the observed deformation patterns