كليدواژه :
الگوي شكست , ريز ترك‌ها , رفتار مكانيكي گرانيت , رفتار مكانيكي نمونه‌هاي سنگي
چكيده فارسي :
درزه ها و ترك ها جزء لاينفك سازه هاي سنگي بوده كه بر اساس نوع كاربري سازه تحت تاثير مجموعه اي از بارهاي استاتيك و ديناميك قرار مي گيرند. يكي از مهمترين عامل گسيختگي سازه هاي سنگي گسترش همين درزه ها و ترك هاي موجود در سنگ مي باشد. ريز ترك ها در سنگ معمولاً به دو شكل طبيعي و القايي مشاهده مي شود. در اين تحقيق، تاثير ريز ترك هاي القايي بر رفتار مكانيكي نمونه هاي سنگي بررسي شده است. براي اين كار از حرارت براي القاي ريزترك در داخل نمونه استفاده شده است سپس آزمون هاي آزمايشگاهي شامل اولتراسونيك، مقاومت فشارشي تك محوره و برزيلي در آزمايشگاه انجام گرفته و الگوي شكست نمونه ها در آزمون مقاومت فشاري تك محوره مورد بررسي قرار گرفته است. نتايج آزمون هاي آزمايشگاهي نشان ميدهد كه الگوي شكست نمونه هاي گرانيتي با افزايش ريز ترك ها از حالت جدايش محوري به حالت شكست برشي تبديل ميشود . به عبارت ديگر افزايش تعداد ريز ترك ها در نمونه هاي گرانيتي باعث تغيير الگوي شكست نهايي نمونه ها از حالت شكست شكننده به شكست شكل پذير مي شود. همچنين با استفاده از نرم افزار rfpa، ناهمگني ناشي از ريزترك ها به صورت عددي مدلسازي شده و تاثير آن بر الگوي شكست نمونه ها مورد بررسي قرار گرفته است. بر اساس نتايج بدست آمده از مدلسازي عددي مشخص گرديد كه علت تغيير در الگوي شكست نمونه هاي سنگي با افزايش ريز ترك هاي القايي، كاهش ترك هاي كششي و افزايش ترك هاي برشي در نمونه ها مي باشد.
چكيده لاتين :
It is seldom possible that rock engineering structures found without joints, cracks, or discontinuities. On the other hand, the application range of these structures are steadily increasing in recent years and includes bridges, tunnels, slopes, underground gas storage. Thereby, their impact is to be considered in the rock structure design. In the present study, it is intended to evaluate the effect of induced micro-cracks on the mechanical behavior of rock specimens. For this purpose, 24 cylindrical specimens of Granit were prepared and some of them heated up to 1000 degrees Celsius to induce micro-crack in the specimens. In the next, Uniaxial compression test for determination of stress-strain curve of heated and unheated specimens were performed based on International Society for Rock Mechanics (ISRM) suggested methods on a cylindrical specimen with 110 mm and 54 mm in length and diameter, respectively. The tests were conducted using a load controlled testing machine and the loading rate was kept at 0.5 MPa/Sec. Results of experimental tests indicated that mechanical properties of heated specimens decrease with increasing the temperature. In the heated specimens, some fractures induced that influence on the failure pattern of specimens. The failure pattern of unheated specimen is axial splitting mode, while the failure pattern of heated specimen up to 1000 degree Celsius changes to shear mode failure. It is seldom possible that rock engineering structures found without joints, cracks, or discontinuities. On the other hand, the application range of these structures are steadily increasing in recent years and includes bridges, tunnels, slopes, underground gas storage. Thereby, their impact is to be considered in the rock structure design. In the present study, it is intended to evaluate the effect of induced micro-cracks on the mechanical behavior of rock specimens. For this purpose, 24 cylindrical specimens of Granit were prepared and some of them heated up to 1000 degrees Celsius to induce micro-crack in the specimens. In the next, Uniaxial compression test for determination of stress-strain curve of heated and unheated specimens were performed based on International Society for Rock Mechanics (ISRM) suggested methods on a cylindrical specimen with 110 mm and 54 mm in length and diameter, respectively. The tests were conducted using a load controlled testing machine and the loading rate was kept at 0.5 MPa/Sec. Results of experimental tests indicated that mechanical properties of heated specimens decrease with increasing the temperature. In the heated specimens, some fractures induced that influence on the failure pattern of specimens. The failure pattern of unheated specimen is axial splitting mode, while the failure pattern of heated specimen up to 1000 degree Celsius changes to shear mode failure. It is seldom possible that rock engineering structures found without joints, cracks, or discontinuities. On the other hand, the application range of these structures are steadily increasing in recent years and includes bridges, tunnels, slopes, underground gas storage. Thereby, their impact is to be considered in the rock structure design. In the present study, it is intended to evaluate the effect of induced micro-cracks on the mechanical behavior of rock specimens. For this purpose, 24 cylindrical specimens of Granit were prepared and some of them heated up to 1000 degrees Celsius to induce micro-crack in the specimens. In the next, Uniaxial compression test for determination of stress-strain curve of heated and unheated specimens were performed based on International Society for Rock Mechanics (ISRM) suggested methods on a cylindrical specimen with 110 mm and 54 mm in length and diameter, respectively. The tests were conducted using a load controlled testing machine and the loading rate was kept at 0.5 MPa/Sec. Results of experimental tests indicated that mechanical properties of heated specimens decrease with increasing the temperature. In the heated specimens, some fractures induced that influence on the failure pattern of specimens. The failure pattern of unheated specimen is axial splitting mode, while the failure pattern of heated specimen up to 1000 degree Celsius changes to shear mode failure.
