Scopus İndeksli Yayınlar Koleksiyonu
Permanent URI for this collectionhttps://hdl.handle.net/20.500.12573/395
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Conference Object Citation - Scopus: 1On the Variation in Several Rock Properties due to Magnesium Sulfate Weathering Tests ‒ A Case Study for Limestones(International Multidisciplinary Scientific Geoconference, 2019-06-20) Köken, E.Contributions to the behavior of rock materials under various conditions provide a practical knowledge about issues relating the performance and long-term serviceability of rocks. In this study, various limestones with varying textural features were investigated in terms of their resistance against magnesium sulfate weathering tests. For this purpose, initial physico-mechanical properties of limestones were determined. Then, rock materials were subjected to magnesium sulfate weathering tests (up to 20 cycles) and the variation in physico-mechanical properties were determined for each rock type. As a result of laboratory tests, compared to initial rock properties, effective porosity (ne, %) increased in the range of 3% ‒ 14% and 12% ‒ 35% after 10th and 20th magnesium sulfate weathering cycles, respectively. Uniaxial compressive strength of rocks (UCS, MPa) decreased by 9% ‒ 24% after 10th cycles and by 32% – 58% after 20th cycles. Brazilian tensile strength of rocks (BTS, MPa) decreased in the range of 7% ‒ 19% and 20% ‒ 49% after 10th and 20th cycles, respectively. Similar to the variations in UCS and BTS, Tangential Young Modulus (Eti, GPa) also decreased at a rate of 13% ‒ 28% and 23% ‒ 64% after 10th and 20th cycles, respectively. However, the values of Tangential Poisson’s Ratio (vti) fluctuated with progressive accelerated weathering cycles, which could be linked to varying axial and lateral strain rates at 50% of UCS values for the limestones investigated. Furthermore, the variation in crack initiation stress σCI (MPa) due to progressive magnesium sulfate tests were also evaluated considering two strain-based methods and the findings showed that σCI of limestones slowly decreased with increasing weathering test cycles. It could be claimed that cyclic magnesium sulfate tests performed on rock materials would be beneficial for assessing the long-term serviceability of rocks. In this context, mud-supported limestones seem to have a greater resistance against magnesium sulfate weathering tests compared to the grain-supported ones. However, the number of samples should be increased in order to achieve a comprehensive understanding about the degradation processes of limestones. © 2021 Elsevier B.V., All rights reserved.Conference Object Citation - Scopus: 2Comparison of Secondary Crushing Operations Through Cone and Horizontal Shaft Impact Crushers(International Multidisciplinary Scientific Geoconference, 2020-09-20) Köken, E.; Qu, JiliIndustrial size reduction processes such as crushing and grinding play vital roles in rock quarrying. The present study states real field data concerning secondary crushing operations through the cone and horizontal shaft impact (HSI) crushers. In this regard, a total of 44 case studies were collected from several rock quarries located in various parts of the world. Based on the field data, crushing performances of the cone and HSI crushers were compared by statistical analyses. The statistical analyses demonstrated that the specific energy consumption of HSI type crushers is relatively higher than those of cone crushers when comparing their production capacities. However, the difference in the specific energy consumption decreases with increasing the Los Angeles abrasion loss (LAA) of rocks. Specifically, the difference closes remarkably up when the LAA approaches 40%. It was also achieved that there is no remarkable superiority over the crushers with a specific energy consumption lower than 0.75 kWh/ton. Furthermore, the maximum feed size for cone and HSI crushers could be estimated at 12% of the mainframe opening and 39% of the rotor diameter, respectively. The ratios statistically found could be declared a start-up. These ratios are, therefore, beneficial for initial sizing related to secondary crushing operations. It was also claimed that for higher achievements in the production capacity (e.g.,> 8000 ton/day), cone crushers could be more feasible for handling rocks whose LAA is lower than 30%. Otherwise, the selection of secondary crushing equipment is associated with rock lithology, its reserve, economic constraints, targets, and marketplaces of rock aggregate manufacturers. © 2021 Elsevier B.V., All rights reserved.