تحليل عددي بستر ماسه ‌يي پي هاي مسلح به ژيوسل و مقايسه‌ي كارايي سيستم هاي تسليح ژيوسينتتيك سلولي و صفحه‌يي

Numerical Analysis of Geocell Reinforced Foundation Sand Beds and Comparison of Cellular and Planar Geosynthetic Reinforcing Systems

ژيوسل ها از انواع ژيوسينتتيك ها هستند، كه با توجه به مزاياي متعدد، استفاده از آن ها درحال توسعه بوده و امروزه مطالعات وسيعي روي آن ها در حال شكل گيري است. مكانيزم رفتاري ژيوسل ها با ژيوسينتتيك هاي صفحه ‌يي كاملاً متفاوت است. آن ها با ايجاد محصوركنندگي جانبي قابل توجه براي خاك (به علت هندسه‌ي سه بُعدي)، خواص مقاومتي آن را به طرز چشم‌گيري ارتقا مي دهند. با وجود مطالعات آزمايشگاهي نسبتاً وسيع در زمينه‌ي ذكرشده، مطالعه‌ي عددي عملكرد ژيوسل ها كه براي درك رفتار دقيق آن ها ضروري است، بندرت انجام شده است. بنابراين علي رغم ويژگي هاي منحصر به‌فرد ژيوسل و استفاده از آن در پروژه هاي راه‌سازي، به دليل نبود روش هاي تيوري و طراحي كافي، اين سيستم تسليح همچنان نتوانسته است جايگاه واقعي خود را در پروژه هاي بهسازي خاك بيابد. لذا در اين پژوهش، به مطالعه‌ي بستر ماسه‌يي پي هاي مسلح به ژيوسل بر مبناي روش عددي تفاضل محدود با استفاده از نرم افزار FLAC3D پرداخته -شده و عملكرد سيستم تسليح ژيوسل و شرايط بهينه‌ي طراحي و اجراي آن در بستر فونداسيون ها مورد مطالعه قرار گرفته است. همچنين كارايي سيستم هاي تسليح سلولي (ژيوسل) نسبت به سيستم هاي تسليح صفحه‌يي به عنوان دو سيستم با جنس يكسان، ولي با مكانيزم رفتاري متفاوت مورد مقايسه قرار گرفته است.

Geocell is a three-dimensional geosynthetic product which can be used to stabilize foundations by increasing bearing capacity and reducing settlements. Geocells have completely different mechanisms compared to the traditional forms of geosynthetics (planar geosynthetics). Their three dimensional geometry causes extreme lateral confinement for the infilled soil, which leads to an increase in soil strength and stiffness and a decrease in surface permanent-deformation. Many laboratory and field tests have demonstrated the effectiveness of geocell reinforcement systems in different fields. Due to several advantages, the geocell is in the process of practical development. However, a considerable gap exists between applications and theories for mechanisms of geocell-reinforced foundations. There are relatively extensive laboratory studies in the field of geocell reinforcement, but, because of its complexity, numerical modeling of geocell reinforcement, which is essential for investigating its behavior, has rarely been undertaken. This paper presents a numerical model of geocell reinforced foundation sand beds. In this numerical study, in order to simulate the three dimensional nature of the geocell accurately, the geocell and soil are simulated separately using the 3D Finite Difference Method (FDM) of FLAC3D. The geocell is simulated using geogrid structural elements, and the elastic–perfectly plastic Mohr–Coulomb model is used for modeling the behavior of soil. In order to verify the modeling, at first, a single geocell reinforced soil is modeled and compared with the equivalent laboratory test presented in the literature. Then, the model is extended to geocell foundation beds. Finally, in this research, the placement conditions under which the geocell layers have the highest efficiency (highest bearing capacity with the least cost) are determined in order to reduce the costs as much as possible. Also, a comparison is made between the performance of the 3D geosynthetic reinforcement and planar form with the same mass of used material (as two reinforcing systems with similar materials but different behavior mechanisms) to determine the system with higher efficiency.