Scientific Mining Journal

ABSTRACT
In this study, Shore hardness, Uniaxial compressive strength and Cerchar abrasivity index tests were applied on sedimentary rocks from two different boreholes in Denizli, Molasse basin. Shore tests and Uniaxial compressive strength tests were applied in Middle East Technical University, Mining Engineering department, rock mechanics laboratory and Cerchar tests were done in Afyon Kocatepe University, Mining Engineering Department laboratories. Totally twelve different sandstone and claystone samples were utilized and the correlation of the variables and fuzzy inference system were also analysed between the parameters. Based on the results, with utilizing three different variables, a multiple linear regression model was created to predict Cercharabrasivity index. Two different prediction results were compared and mentioned in the study.

ABSTRACT
In this research, some physical and mechanical changes in Ä°scehisar andesites produced in Afyonkarahisar region were investigated because of destructive effects of salts. For this purpose, petrographic-mineralogical (polarizing microscope, XRD), chemical analysis, pore diameter distribution and physico-mechanical properties of andesites were determined. In the second step, the same experiments were repeated in the case of andesite samples using water repellent and protective chemical substances to prevent water absorption and consequently salt crystallization.
The amounts of decomposition due to salt crystallization events of the andesite samples were determined by the changes in mechanical and physical properties like weight loss, ultrasonic velocity and uniaxial compressive. Mean dry weight loss was 0.3695% in normal samples and 0,186% mass increase in water-repellent samples. Compressive strength values were found tobe 32% for normal samples and 37% for water repellent chemically treated samples.

ABSTRACT
In this study, extensive sampling campaign was performed around the crushing-screening circuit of an aggregate plant in Turkey in order to performance evaluation and optimization. According to results of performance evaluation studies, vertical shaft impactor (VSI) is running within average reduction ratio values. But, the reduction ratio of the cone crusher was lower. Decreasing close side setting (CSS) of cone crusher increases the reduction ratio. Screen performances were decreasing by increasing feed capacity. Then, all equipment in the circuit were modelled individually by using the appropriate model structures. Model and mass balance results were very close to each other. After modelling, two different simulation studies were performed
separately. As a result of first simulation study, the reduction ratio of cone crusher increases by decreasing CSS, therefore; the cone crusher screen group performance also increases. As a result of second simulation study, the plant capacity can be increased 15% by changing finescreen aperture from 5 mm to 6 mm without any deterioration in the product quality.

ABSTRACT
High-value-added micronized quartz production can be possible by removing the impurities of -100 micron by-product composition which is obtained from glass sand enrichment plants. In this study, it was aimed to produce high quality silica concentrate from such a product. For this purpose, low alumina content pre-concentrate was obtained with 0.12% Fe2O3 iron content using clay separation process. As a result of acidic leaching experiments with oxalic acid which was performed on this pre-concentrate, a silica concentrate was produced with 99.16% SiO2, 0.04% Fe2O3, and 0.53% Al2O3 contents. In addition, according to the kinetic study based on the temperature-time relationship, it was determined that the dissolution of iron in oxalic acid medium occurred by a chemical controlled reaction.

ABSTRACT
Today, powered roof supports that are designed in 1950s have become the most important equipment in longwall mining once supporting speed reached the excavation speed. In order to support the roof efficiently by the support unit, the canopy has to be in full contact with the roof strata in longwalls. But in some cases, such as irregular roof loadings, soft footwall, and loads coming from gob, canopy and roof strata can not be in full contact.
In this study, maximum stresses occurring on support unit parts are calculated in different contact states between canopy and roof strata and the working efficiency of roof support units are evaluated. According to the four different contact situations designed in the scope of the study, it is seen that the powered roof support unit provided the most efficient working condition in the full contact state between canopy and roof strata.

ABSTRACT
The purpose of the study is to assess the grinding and classification performance of a conventional Polysius® two-compartment ball mill and a Sepol® dynamic air classifier closed circuit process at Portland CEMI/42.5R and Portland composite CEMII/32.5R cement production types. For this purpose, industrial scale sampling surveys were performed around the circuit. JKSimMet Steady State Mineral Processing Software was used to perform mass balance around the circuits. Size reduction performance of the ball mill was determined for the sampling cases. Classification performance of the dynamic air classifier was evaluated based on the efficiency
curve approach. It was determined that, approximately 12% circuit capacity increase could be achieved in composite cement production when ball mill, ball mill filter and air classifier power consumptions were considered. This figure corresponded to overall energy savings of 7% in ball mill grinding.