جستجوی مقالات مرتبط با کلیدواژه « coarse » در نشریات گروه « عمران »
تکرار جستجوی کلیدواژه «coarse» در نشریات گروه «فنی و مهندسی»-
در اجرای یک سازه ی خاک مسلح، برای بالابردن راندمان مسلح کننده ها، معمولا از خاک های درشت دانه استفاده می شود. خاک های درشت دانه به علت ویژگی های ذاتی که دارند با چشمه های مسلح کننده بهتر درگیر می شوند، اما عموما از محل قرضه به محل اجرای پروژه منتقل شده و از این جهت تهیه ی آنها پرهزینه است. به همین دلیل در این تحقیق سعی شده است که فقط لایه یی از خاک درشت دانه در اطراف مسلح کننده استفاده شود وحجم باقیمانده با خاک محل یا خاک ریزدانه جایگزین شود. در این نوشتار، نتایج آزمایش های بیرون کششپانویس{p u l l-o u t} که بر روی ژئوگرید معمولی و مسلح کننده ی مهار شبکهپانویس{g r i d-a n c h o r} انجام شده اند، ارائه شده است و با مقایسه ی نتایج این آزمایش ها، ضخامت تقریبی بهینه برای لایه ی خاک درشت دانه ی اطراف مسلح کننده به دست آمده است. در نهایت، نتایج تحلیل عددی، با استفاده از نرم افزار اجزاء محدود D T u n n e l3P l a x i s، از طریق مقایسه با نتایج تحلیل آزمایشگاهی به تایید رسیده اند.
کلید واژگان: آزمایش بیرون کشش, ژئوگرید, مهار, شبکه, خاک ریزدانه, خاک درشت دانه, ضخامت بهینه, نرم افزار اجزاء محدود D T U N N E L3 P L A X I S}In order to increase the efficiency of reinforcements in a reinforced soil structure, the granular soils are usually used. However, in the most situations, we have to transfer granular soils from the borrow area, usually far from the site of the soil structures. This will impose a considerable amount of money to the project. Therefore, in this research, just a layer of coarse-grained soil, surrounding the reinforcement layer is used and the remained volume was filled with the fine-grained soils or the soils that exist in the project site. This experimental study is performed for the selected thicknesses of coarse-grained soil surrounding the reinforcement. Furthermore, the numerical analysis for these pull-out tests was conducted using the finite element code, PLAXIS3D Tunnel. Finally, the experimental and numerical analysis results for the variety of coarse soil thicknesses were compared and the optimum thicknesses for coarse-grained soil are presented. According to the results, the pull-out resisting force increases with increasing the coarse layer thickness; in addition, the Grid-Anchor endures more pull-out resisting forces as compared with the usual geogrid. According to the experimental results, 10 centimeters coarse layer (i.e. the thickness of 5 centimeters for the top and the thickness of 5 centimeters for the bottom layer of the reinforcements) was found as optimum thickness of surrounding layer for the 5 kPa surcharge. Other findings of this research can be as follows: when the reinforcements begin to move against the soilsurrounding them, the pull-out resisting force decreases due to the decrease in friction between the soil and the reinforcements. On the other hand, as the thickness of coarse layer around the reinforcements increases, a hardening state in the force-displacement curve of these reinforcements was observed. This situation is more visible for Grid-Anchor in comparison with the usual geogrid. Having compared the numerical and experimental results, there is a suitable conformance between them.
Keywords: Pull, Out Test, Geogrid, Grid, Anchor, Fine, Grained Soil, Coarse, Plaxis3d Tunnel} -
Iranian Journal of Science and Technology Transactions of Civil Engineering, Volume:38 Issue: 1, 2014, PP 285 -296This paper developed a new elastoplastic model for coarse-grained soils. Plastic potential surface was established by solving a differential dilatancy equation, which is obtained via the triaxial test results. This model obeys a non-associated flow rule; therefore, the yield surface is not consistent with the plastic potential surface. Expression of the yield surface was established similar to the plastic potential surface, but its shape is influenced not only by the stress ratio η, but the mean stress p. A unified hardening parameter that is independent of stress path is adopted, so that negative dilatancy and positive dilatancy properties of coarse-grained soils could both be described. In this research, elastoplastic formula of the proposed model is deduced. This model was also evaluated with several groups of test results under different stress paths (i.e. conventional triaxial tests, constant mean stress test and constant stress ratio test, etc.). Results showed that model predictions agree well with the test results.Keywords: Elastoplastic model, coarse, grained soils, dilatancy equation, non, associated flow rule, unified hardening parameter, stress path}
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