تأثیر نوع تکیه‌گاه بار-جابجایی آزمایش خمش نیم‌دایره‌ای بر پارامترهای مختلف مکانیک شکست مخلوط‌های آسفالتی

نوع مقاله : مقاله پژوهشی

نویسندگان

1 دانشگاه علم‌وصنعت ایران، تهران، ایران

2 دانشگاه صنعتی نوشیروانی بابل

3 دانشگاه علم وصنعت ایران، مهندسی عمران

چکیده

امروزه آزمایش خمش نیم‌دایره‌ای به عنوان یک روش مرسوم در بررسی رفتار شکست مخلوط آسفالتی مورد استفاده قرار می‌گیرد. این آزمایش مطابق آیین‌نامه‌ها دارای شرایط خاص آزمایشگاهی از جمله ابعاد هندسی نمونه، دمای آزمایش و نرخ بارگذاری مشخصی می‌باشند که در آزمایشگاه‌ها و مؤسسات تحقیقاتی با ایجاد شرایط یکسان رعایت می‌شوند. ولی در کنار فراهم‌سازی شرایط یکسان آزمایش، شکل و نوع تکیه‌گاه‌ها مورد استفاده در آزمایش کمتر مورد توجه قرار گرفته و دارای نوع و شکل یکپارچه‌ای نمی‌باشند که ممکن است این امر موجب تفاوت در نتایج آزمایشگاهی گردد. لذا در این پژوهش تأثیر 5 نوع تکیه‌گاه مختلف بر روی پارامترهای مهم مکانیک شکست مخلوط آسفالتی با در نظر گرفتن ضریب تغییرات مورد بررسی قرار گرفت. نرخ بارگذاری مورد استفاده برابر 5 میلی‌متر بر دقیقه در نظر گرفته شد و نمونه‌های آسفالتی ساخته شده تحت بارگذاری استاتیکی یکنواخت مود І خالص قرار گرفت. نتایج آزمایش نشان داد انتخاب نوع تکیه‌گاه تأثیر مستقیمی بر روی پارامترهای مکانیک شکست دارد و انتخاب تکیه‌گاه اشتباه ممکن است خطای قابل توجهی وارد نتایج آزمایش کند و همچنین وجود اصطکاک در بین نمونه و تکیه‌گاه موجب پراکندگی بیشتر نتایج آزمایشگاهی شده و میزان تکرارپذیری نتایج را کاهش دهد. بدین منظور پیشنهاد می‌شود تکیه‌گاه‌های صلب که آزادی حرکت ندارند و دارای اصطکاک زیادی با نمونه هستند، در حد امکان مورد استفاده قرار نگیرند. در این تحقیق مطابق نتایج با در نظر گرفتن شرایط آزمایشگاهی خاص (هندسی نمونه، دمای آزمایشگاهی و نرخ بارگذاری مشخص) تکیه‌گاه شماره 1 به عنوان مناسب‌ترین تکیه‌گاه با تکرارپذیری بالای نتایج انتخاب شد.

کلیدواژه‌ها

موضوعات


عنوان مقاله [English]

The Effects of SCB test support configurations on different fracture mechanic parameters in asphalt mixtures

نویسندگان [English]

  • Ali Mirhashemi 1
  • Saeid Sobhi 2
  • Pooyan Ayar 3
  • afshar yusefi 1
1 Iran University of Science and Technology, Tehran, Iran
2 Babol Noshirvani University of Technology
3 School of Civil Engineering, Building No.2, Iran University of Science and Technology, Narmak, Tehran 16846-13114, Iran.
چکیده [English]

Today, the semi-circular bending (SCB) test has become a common method and is used in studying the mechanical behavior of asphalt mixtures. According to the regulations, this test has specified laboratory conditions such as sample geometry, test temperature and a certain loading rate. However, in addition to providing these conditions for SCB testing, the shape and type of supports used in the experiment are less considered and they do not have an integrated type and shape, which may cause differences in laboratory results. Therefore, in this study, the effects of 5 different support configurations on important parameters of fracture mechanics at intermediate temperatures were investigated by considering the coefficient of variation (CV). The used loading rate was selected 5 mm/min in which the asphalt samples were subjected to uniform static loading under mode I. The experimental results showed that the selection of support type has a direct influence on the fracture mechanic parameters, while the selection of the wrong support type may cause significant error in the test results. Nevertheless, the friction between the sample and the support causes more dispersion in the test results and could reduce its repeatability. For this purpose, it could be recommended not to use rigid supports that have considerable friction with the sample. Finally, considering specific laboratory conditions for the SCB test (i.e., sample geometry, test temperature and specific loading rate), support No. 1 was selected as the most suitable support with high repeatability of the results.

کلیدواژه‌ها [English]

  • Semi-Circular Bending (SCB) test
  • Support Configurations
  • Fracture Mechanics
  • Asphalt Mixture
  • Coefficient of Variation (CV)
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