Time filter

Source Type

Karakul H.,General Directorate of Mineral Research and Exploration | Ulusay R.,Hacettepe University | Isik N.S.,Gazi University
International Journal of Rock Mechanics and Mining Sciences | Year: 2010

This study aims to investigate the strength anisotropy associated with discontinuity orientation by performing block punch index (BPI) tests and uniaxial compressive strength (UCS) tests, and to develop some empirical relationships for estimating the BPI and UCS in the strongest direction, and the UCS from the BPI determined at any angle between the loading direction and weakness plane. The experimental results obtained from six rock types show that these rocks fall into the moderate-to-low strength anisotropy classes. The comparison between the observed and predicted UCS values indicated that the prediction performances of the equations developed are quite good. Numerical simulations revealed that numerically estimated BPI values are very close to experimentally determined values for each angle between the loading direction and the weakness planes involved by the BPI specimens. As the angle between the weakness planes and loading increases, plastic zones become wider and unsymmetrical. The results of this study are also applicable to anisotropic rocks outside the strength ranges of the rocks studied by the authors, but their degree of anisotropy should be in the range of low-to-moderate. © 2010 Elsevier Ltd.

Ozguven A.,General Directorate of Mineral Research and Exploration | Ozcelik Y.,Hacettepe University
Engineering Geology | Year: 2014

It is known that fire and high temperatures cause degradation of natural building stones. There are many studies focused on the effect of high temperature on physico-mechanical properties of sandstone and granites while there are a few insufficient studies on limestones and marble. Almost all of the studies performed on limestone and marble are established at temperatures lower than 1000. °C and just focused on investigating some of the physico-mechanical properties of natural building stones and therefore some of the physical and mechanical properties of limestones and marbles exposed up to this temperature are not studied in detail. That condition cannot explain how the properties of marble and limestone change with high temperatures, which are widely used in many areas of our lives as building materials. The aim of this study is to investigate the changing of physico-mechanical properties of natural building materials including limestone and marbles exposed to different temperatures ranging from room temperature up to 1000. °C in the oven. For this purpose, samples were exposed to the heat separately starting from 200. °C, gradually 400, 600, 800 and 1000. °C and then some physico-mechanical properties of them and reference sample at room temperature were determined. The results obtained from the tests were analyzed in detail in terms of criticality of temperature degree, positive or negative effect of temperature rise, reusability of the building stone exposed to heat.As a conclusion of the study, important results are given in many aspects such as, usage areas of fire exposed natural stones, safety precautions at usage areas in addition to gained properties of natural stones due to temperature. © 2014 Elsevier B.V.

Sutcu E.C.,General Directorate of Mineral Research and Exploration | Karayigit A.I.,Hacettepe University
International Journal of Coal Geology | Year: 2015

The Afşin-Elbistan coal basin is one of the most important coal deposits of Turkey. The mineral matter, major and trace element concentrations of the Afşin-Elbistan coals and their modes of occurrence are discussed in this study. The coal seam is located within the Upper Miocene-Pliocene aged Ahmetcik Formation which is represented by fluvial-lacustrine facies. Thickness of the coal zone is 80. m, but it reaches 105. m in the Kişlaköy sector. A total of 86 samples were taken from the Kişlaköy open-pit mine and from the 14 boreholes drilled by the General Directorate of Mineral Research and Exploration (MTA) for coal exploration. The proximate, XRD, SEM-EDS, major and trace element analyses were conducted on the samples. The studied coals are characterized by relatively high moisture, ash, total sulfur, volatile matter contents and low gross calorific values. The mineral matters of the Afşin-Elbistan coal are represented by calcite, quartz, pyrite, feldspar, aragonite, opal-CT, gypsum, jarosite and clay minerals. Strontium, Rb, Sm, Zr, Hf, Nb, Mo, U, Zn, Pb, As, Mn, Co, Cr and Ni concentrations detected by EDP-XRF are higher than the world brown coal values. Many of the trace elements showing positive correlations with ash content imply inorganic affinity. The element concentrations of the coals are mainly related to the carbonate, silicate, sulfide, phosphate, ore minerals and fossil shells. However, some elements have also organic affinities. © 2015 Elsevier B.V.

Ozguven A.,General Directorate of Mineral Research and Exploration | Ozcelik Y.,Hacettepe University
Construction and Building Materials | Year: 2013

Under the influence of fire and other high heat sources, a number of changes occur in natural stones. These changes vary according to the values of the temperature exposure. Therefore, this study aims to understand the effect of heat in a fire and high temperatures on some properties of limestone and marble, as they are widely used natural building stones. For this purpose, eight natural stones (four limestone and four marble) of different origins and textural characteristics were exposed to 200, 400, 600, 800 and 1000 °C temperature in the oven. After each exposure, the rock properties were determined and compared with the properties at room temperature. Discoloration and whiteness, polish reception, daily physical change, variation of pH and temperature of the cooling solution were taken into account in the comparison. As a result of this study, the positive and negative aspects of the property changes that occur in natural stones which are exposed to different temperatures are discussed. © 2012 Elsevier Ltd. All rights reserved.

Nefeslioglu H.A.,General Directorate of Mineral Research and Exploration | Gokceoglu C.,Hacettepe University
Mathematical Problems in Engineering | Year: 2011

The aim of the present study is to introduce a probabilistic approach to determine the components of the risk evaluation for rainfall-induced earthflows in medium scale. The Catakli catchment area (Cayeli, Rize, Turkey) was selected as the application site of this study. The investigations were performed in four different stages: (i) evaluation of the conditioning factors, (ii) calculation of the probability of spatial occurrence, (iii) calculation of the probability of the temporal occurrence, and (iv) evaluation of the consequent risk. For the purpose, some basic concepts such as Risk Cube, Risk Plane, and Risk Vector were defined. Additionally, in order to assign the vulnerability to the terrain units being studied in medium scale, a new more robust and more objective equation was proposed. As a result, considering the concrete type of roads in the catchment area, the economic risks were estimated as 3.6 × 10 6 €-in case the failures occur on the terrain units including element at risk, and 12.3 × 106 €-in case the risks arise from surrounding terrain units. The risk assessments performed in medium scale considering the technique proposed in the present study will supply substantial economic contributions to the mitigation planning studies in the region. © 2011 H. A. Nefeslioglu and C. Gokceoglu.

Karakul H.,General Directorate of Mineral Research and Exploration | Ulusay R.,Hacettepe University
Rock Mechanics and Rock Engineering | Year: 2013

Determination of P-wave velocity (V p), which is closely related to intact rock properties both in laboratory and in situ conditions, is a non-destructive, easy and less complicated procedure. Due to these advantages, there is an increasing trend to predict the physico-mechanical properties of rocks from V p. By considering that no attempt on the estimation of mechanical properties of rocks from V p under different degrees of saturation has been made, in this study, it was aimed to correlate strength properties (uniaxial compressive and tensile strengths) with V p of various rock types under different degrees of saturation. For this purpose, fourteen different rock types were collected from several parts of Turkey and a comprehensive laboratory testing program was conducted. Experimental results indicated that strength and deformability properties of the rocks decreased with increasing degree of saturation, while V p showed increasing and decreasing trends depending on degree of saturation. Simple regression analysis results indicated that although prediction of the strength properties of rocks directly from V p at different degrees of saturation was possible, the equations developed would yield some under- or over-predictions. In the second stage of statistical analyses, a series of different prediction relationships were developed by using independent variables such as V p, degree of saturation and effective clay content (ECC). The statistical tests suggested that the resultant multivariate equations had very high prediction performances and were very useful tools to estimate the strength properties from V p determined at any degree of saturation. In addition, the comparisons between the theoretical Gassmann-Biot velocities, which were calculated at different degrees of saturation, and the experimental results suggest that the theoretical Gassmann-Biot velocities show inconsistencies with the experimental results obtained from the investigated rock types with high ECC. Therefore, it was concluded that the use of theoretical velocities is not suitable for rock types with high ECC. © 2013 Springer-Verlag Wien.

Ozguven A.,General Directorate of Mineral Research and Exploration | Gunduz L.,Suleyman Demirel University of Turkey
Cement and Concrete Composites | Year: 2012

It is important to know which parameters are effective for the manufacture of expanded clay aggregate and to determine how effective these parameters are on expansion. In this study, expansion tests were conducted by using samples from three separate fields to determine how different parameters influence manufacturing. Clay grain size, pellet size, temperature in the furnace and firing time were selected in the expansion tests as parameters. Their effect on production was evidenced separately. It was found that decreasing the clay size has a positive effect on expansion while a decrease in pellet size has a negative effect on it. Also, temperature in the furnace and the time period during which the clay remains in the furnace are critical values for the resultant aggregate quality. The conditions for optimum manufacturing were explained in detail. © 2012 Elsevier Ltd. All rights reserved.

Ozguven A.,General Directorate of Mineral Research and Exploration
Applied Clay Science | Year: 2014

The main aim of this study is to establish optimum working conditions and to propose expandability charts for Kalecik Clay using expansion ratio versus unit volume weight values via a statistical computer program (Design Expert 7.0). First of all, some suitable samples were collected from the Kalecik County (Ankara, Turkey). Later, the samples were crushed and milled up to 200. μm clay size in the laboratory. Then, pellets with a 10. mm diameter were dried in ovens and heated inside a furnace to expand in different temperatures. One heating operation began with 900. °C and ended with 1200. °C. In addition to that, the holding time periods were selected as 5, 10, 15 or 20. min for each operation. In the final stage, the unit volume weight and expansion ratio of the produced aggregates were determined.As results of this study, both the optimum furnace holding time and furnace temperature values for the samples were determined in order to maximize the expansion ratio values and minimize the unit volume weight for Kalecik Clays. Some expandability charts were proposed for Kalecik Clay by using the findings.The charts allow one to assign expansion ratio and unit volume weight values in different working conditions including holding time inside the furnace and furnace temperature. The proposed charts are expected to be quite useful for more efficient production of expanded clay aggregates in construction industry. © 2014 Elsevier B.V.

Gurboga S.,General Directorate of Mineral Research and Exploration
International Geology Review | Year: 2016

The present-day tectonic framework of Turkey comprises mainly two strike-slip fault systems, namely dextral North Anatolian and sinistral East Anatolian faults. They are considered as the main cause of deformation patterns in Anatolia. These two mega shear systems meet at Kargapazarı village of Karlıova county. The area to the east of the junction has a transpressional tectonic regime between the Eurasian and Arabian plates and is characterized, based on field observation, by a network of faults defining a typical horsetail splay structure. The horsetail splay is interpreted as marking the termination of the North Anatolian Fault System (NAFS), which continues eastward into the Varto Fault Zone (VFZ) and then dies out. The present study reveals that the VFZ is made up of two main parts, namely the principal displacement zone (PDZ) and the transpressional splay zone (TPSZ), both characterized by the right-lateral strike-slip with reverse motion. However, the area to the east of Varto is characterized dominantly by reverse-thrust faults and E–W-trending faults as shown by focal mechanism solutions. The generation of the VFZ as a transpressional termination to the NAFS can be related directly to the block movements of the Eurasian, Anatolian, and Arabian plates. © 2016 Informa UK Limited, trading as Taylor & Francis Group.

Sutcu E.C.,General Directorate of Mineral Research and Exploration | Toprak S.,General Directorate of Mineral Research and Exploration
International Journal of Coal Geology | Year: 2013

A suberinitic coal was discovered by coincidence during drilling for geothermal research in the Germencik area. Drilling activity showed that the coal was 6-m in thickness on the upper part of the Miocene-aged basal conglomerate unit, which is one of the important geothermal reservoir rocks in the Germencik area.Petrographic, FT-IR, XRD, chemical and SEM analyses were conducted to reveal the detailed properties of the suberinitic coal. The coal is composed entirely of suberinite and phlobaphinites which are part of cork tissue. These tissues also include features such as lamination and micro-folding. Well-preserved cork tissues and bark textures were observed abundantly in the coal samples. Jarosites, gelified cork tissues, are the most common alteration products observed in the coal samples. FT-IR analysis showed that suberinitic coal contains distinct peaks in the aliphatic C-H stretching bands. SEM analysis reveals suberinitic textures and framboidal pyrite inclusions, indicating metallic sulfur mineral sources.Hydrothermal fluids have important controls on the composition of the Germencik area coals. Geothermal reservoir conditions affected coal rank and caused an increase in reflectance values as well as calorific values. Framboidal pyrites probably formed by means of geothermal water and associated mineralization in the region. © 2013 Elsevier B.V.

Loading General Directorate of Mineral Research and Exploration collaborators
Loading General Directorate of Mineral Research and Exploration collaborators