ارزیابی تاثیر ناهمسانی بر سختی برشی با رویکرد انرژی مستهلک شده

نوع مقاله : علمی - پژوهشی

نویسنده

استادیار، دانشگاه شهید بهشتی، دانشکدة مهندسی عمران آب و محیط زیست

چکیده

سختی برشی دینامیکی از پارامترهای مهم در تعیین رفتار خاک‌ها در آنالیز ساختگاه تحت جنبش نیرومند زمین است. در طول بارگذاری دینامیکی مقدار سختی برشی دینامیکی به دلیل افت مقاومت خاک ناشی از اعمال بارگذاری سیکلی کاهش می‌یابد. از طرفی رفتار خاک به دلیل ماهیت ناهمسان آن وابسته به جهت محور بارگذاری است. بنابراین برای مدلسازی صحیح رفتار خاک می‌بایست مقدار سختی در شرایط ناهمسان را تعیین کرد تا مدل‌های رفتاری که قادر به اعمال ناهمسانی هستند بتوانند رفتار دقیق خاک را پیش بینی کنند. استفاده از مدل‌های بر پایه انرژی راه حل مناسبی برای تعیین مقدار پارامترهای مدل در شرایط مختلف بارگذاری هستند. در این تحقیق مقادیر سختی برشی دینامیکی بدست آمده از آزمایش‌های برش پیچشی تناوبی انجام شده بر روی ماسه های متراکم بابلسر و تویورا با هم مقایسه شده و تاثیر جهت تنش اصلی حداکثر بر روی آن‌ها مشخص شده است. در ادامه با استفاده از مدلهای برپایه انرژی، روند تغییرات سختی برشی در شرایط مختلف بارگذاری بررسی شد. نتایج نشان داد که جهت محور تنش اصلی حداکثر، تاثیر زیادی بر روی سختی برشی دینامیکی دارد. از سوی دیگر، در صورت استفاده از رویکرد انرژی مستهلک شده می‌توان به یک رابطه واحد برای توسعه سختی برشی با کرنش برشی رسید.

کلیدواژه‌ها

موضوعات


عنوان مقاله [English]

Evaluation of the effect of anisotropy on the shear modulus with dissipated energy approach

نویسنده [English]

  • Mostafa Zamanian
Assistant professor, Department of Civil, Water and Environmental Engineering, Shahid Beheshti University
چکیده [English]

Dynamic shear stiffness is a key parameter for determining the soil behavior for site analysis under strong ground motion. The dynamic shear modulus reduces during cyclic loading due to the loss in the soil shear strength. Besides, the soil behavior depends on the loading direction due to the anisotropic nature of the soil. Thus, the anisotropic shear stiffness should be determined for accurate modeling of the soil in the models able to incorporate the anisotropy to estimate the soil's behavior. The models based on the dissipated energy are appropriate for determining the model parameters at different loading conditions. In this study, the shear stiffness of dense Babolsar and Toyoura sands obtained from torsional shear apparatus have been compared, and the effect of major principal stress has been evaluated. The specimens were similarly prepared to the relative density of 75% and then isotopically consolidated before shearing. The shear stress was applied in a stress-controlled manner under a unique deviator stress ratio but at different major principal stress directions. The variation of shear stiffness under different loading direction were evaluated. Results indicated that the major principal stress direction has a significant influence on the dynamic shear stiffness. On the other hand, a unique relationship for the evolution of shear stiffness can be obtained using the dissipate energy approach.

کلیدواژه‌ها [English]

  • Shear stiffness
  • Anisotropy
  • Dissipated energy
  • Sand
  • Cyclic loading
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