پديد آورندگان :
محمدي حسين آبادي، مهدي دانشگاه تربيت مدرس , خادمي حميدي، جعفر دانشگاه تربيت مدرس - گروه استخراج معدن , رستمي، جمال مدرسه عالي معادن كلرادو - دانشكده مهندسي معدن , گشتاسبي گوهرريزي، كامران دانشگاه تربيت مدرس - گروه مكانيك سنگ
كليدواژه :
تيغه اسكنه اي , قابليت برش سنگ , آزمون برش خطي سنگ , روش نظري ايوانس
چكيده فارسي :
به منظور تعيين قابليت برش (Cuttability) سنگ، آگاهي از مقدار نيروهاي وارد شده به لبه تيغه در محل تماس آن با سنگ و حجم خرده‌هاي حاصل از حفاري اهميت دارد. تخمين اين نيروها با روش‌هاي تحليلي و آزمون‌هاي آزمايشگاهي برش سنگ امكان پذير است. در اين مقاله، با انجام آزمون‌هاي برش خطي روي چهار نمونه سنگ با مقاومت ضعيف تا متوسط به وسيله يك تيغه اسكنه‌اي (chisel)، نيروهاي برشي حداكثر و ميانگين وارد بر تيغه در حين برش سنگ اندازه‌گيري و با مقادير محاسبه شده از روش نظري ايوانس (Evans) مقايسه شد. نتايج نشان داد كه با افزايش عمق برش، هر سه نيروي برشي حداكثر، ميانگين و نيروي برشي ايوانس به‌طور خطي افزايش مي‌يابد و در يك عمق برش مشخص، معمولاً مقدار نيروي برشي ايوانس كمتر از مقدار نيروي برشي حداكثر و بيشتر از نيروي برشي ميانگين به‌دست‌آمده از آزمون برش خطي است. همچنين مقدار نسبت نيروي برشي حداكثر به نيروي برشي ميانگين ارتباط مستقيمي با افزايش عمق برش دارد و در طراحي ماشين حفاري بايد موردتوجه قرار گيرد، به طوري كه مقدار آن بين 1/16 تا 1/49 براي عمق برش 1 ميلي‌مترو نزديك 1/7 براي عمق برش 4 ميلي‌متربه دست آمد. همچنين نتايج نشان داد كه اين نسبت با افزايش درجه شكنندگي سنگ افزايش مي‌يابد و كم‌ترين مقدار اين نسبت مربوط به نمك با شكنندگي 4/82 و بيشترين مقدار آن مربوط به زغال سنگ با شكنندگي 11/86 است.
چكيده لاتين :
This study deals with an experimental study to determine the performance of chisel tools by performing a set of small-scale linear cutting tests. The average and maximum cutting forces are measured and compared with Evans’s theoretical values. Also, the cutter force and specific energy values are correlated with rock properties. The findings showed a good agreement with previous studies.
Introduction
To date, various methods have been developed and introduced to determine the rock cuttability and machine performance, such as measuring the forces on the cutting tool, calculation of specific cutting force (Fc/d) and specific energy (SE) based on measured forces during the test. One of the most important factors in the design of excavation machines is the ratio of maximum cutting force to mean cutting force, which is related to the depth of cut.
Methodology and Approaches
Linear cutting tests were carried out in unrelieved mode at cutting depth of 1, 2, 3 and 4 mm, on four rock samples (sandstone, marl, salt, and coal), ranging from very low to moderate strength. Each cut is replicated at least 3 or 4 times. The magnitude of cutting force (Fc) generated on the front edge of chisel tool during cutting was recorded and the specific energy calculated based on it. Results and Conclusions
It was found in this study that, as the depth of cut increases, both laboratory (maximum and mean) and theoretical cutting force increase directly. Usually the theoretical cutting force is between the mean and maximum cutting force obtained with the LCM. The ratio of maximum cutting force to mean value was linearly correlated with cutting depth for different samples and varied between 1.16 to 1.49 for d=1mm and near 1.7 for d=4 mm. Also, this ratio increased with increasing brittleness value (σc/σt). The laboratory results indicated that a direct correlation exists between specific energy and cutting force with uniaxial compressive strength and Brazilian tensile strength. Furthermore, these findings showed that the tensile strength is more affective on cutting force than compressive strength which supports the findings of Evans. Finally, the results of studies and matching of results with observations in mines and actual applications, as well as previous studies, indicate the capability of the LCM made in Tarbiat Modares University to measurement of cutting forces and energy. Therefore, it is possible to optimize the excavation tools and machines with different applications in mining and tunnel industries in Iran.
