Ali Osman Yilmaz

Technical Assessment of Renewable Sources for Energy Use in Turkey

The aim of present article is to investigate use of renewable sources for energy in Turkey. Turkey also has a large potential for renewable energies. Turkey has a considerably high level of renewable energy resources that can be a part of the total energy network of the country. The most important renewable sources for Turkeys energy sector are solar in its various forms, wind, biomass, hydro, and geothermal. Renewable sources are the second largest source for energy production after coal. About two thirds of the renewable energy produced is obtained from biomass, while the rest is mainly from hydroelectric energy. In 2003, 25.18% of total electricity production was provided by hydroelectric energy. According to the estimates of the Turkish Ministry of Energy and National Sources, an increase in the production of renewable energy is expected, while a decrease is predicted in total energy requirements.

A Novel Mobile Testing Equipment for Rock Cuttability Assessment: Vertical Rock Cutting Rig (VRCR)

In this study, a new mobile rock cutting testing apparatus was designed and produced for rock cuttability assessment called vertical rock cutting rig (VRCR) which was designed specially to fit into hydraulic press testing equipment which are available in almost every rock mechanics laboratory. Rock cutting trials were initiated just after the production of VRCR along with calibration of the measuring load cell with an external load cell to validate the recorded force data. Then, controlled rock cutting tests with both relieved and unrelieved cutting modes were implemented on five different volcanic rock samples with a standard simple-shaped wedge tool. Additionally, core cutting test which is an important approach for roadheader performance prediction was simulated with VRCR. Mini disc cutters and point attack tools were used for execution of experimental trials. Results clearly showed that rock cutting tests were successfully realized and measuring system is delicate to rock strength, cutting depth and other variables. Core cutting test was successfully simulated, and it was also shown that rock cutting tests with mini disc cutters and point attack tools are also successful with VRCR.

Relationships between the drilling rate index and physicomechanical rock properties

The drilling rate index (DRI) is an important parameter that influences the drillability of rocks. It can easily be used when estimating the economics of any excavation operation. Therefore, in the current study, an attempt was made to investigate the rock properties that govern the DRI. The relationships between the DRI and some physicomechanical rock properties were investigated based on data obtained from experimental work and in situ studies performed in different tunnels. Regression analysis was employed to develop models for estimating the DRI based on physicomechanical rock properties. The derived models were verified based on the behavior of the determination coefficient, the t test, and the F test. The study showed that the DRI decreases with increasing uniaxial compressive strength, point load strength, Brazilian tensile strength, and Schmidt rebound hardness. It was also concluded that the DRI increases with increasing apparent porosity and void ratio. Additionally, modeling results revealed that the proposed models can be successfully used as tools to forecast the DRI.

Correlation between Cerchar abrasivity index, rock properties, and drill bit lifetime

The Cerchar abrasivity index (CAI) is one of the most widely known index method for identification of rock abrasivity. It is a simple and fast testing method providing reliable information on rock abrasiveness. In this study, the relationships between the CAI and some rock properties such as uniaxial compressive strength (UCS), point load strength, Brazilian tensile strength and Schmidt rebound hardness, and equivalent quartz content (EQC) are examined. The relationships between the CAI and drill bit lifetime is also investigated and the type of drill bit wear observed is mentioned. Additionally, the CAI is modeled using simple and multiple linear regression analysis based on the rock properties. Drill bit lifetime is also modeled based on the CAI. The results show that the CAI increases with the increase of the UCS, point load strength, Brazilian tensile strength, L-type and N-type Schmidt rebound hardness, and the EQC. It is concluded that the higher and the lower bit lifetime are obtained for marl and andesitic-basaltic formation, respectively. Moreover, flushing holes, inserted button, button removal, and failures of button on the bits are determined as the type of drill bit wear. The modeling results show that the models based on the UCS and the EQC give the better forecasting performances for the CAI.

Coal Potential of Turkey: Coal and Energy

Coal is one of the largest energy resources of Turkey. Turkey has hard coal reserve of 1.12 billion tons and lignite reserve of 8.05 billion tons. While it is the 9th country in the world in terms of lignite reserve, it is the 8th country in terms of production (Hard coal + lignite) and the 12th country in terms of total coal consumption. While its hard coal production meets only 13% of its consumption, it meets its total lignite consumption. 65% of hard coal production and 78% of lignite production are used for electricity production. Turkeys Total installed capacity is 65587 MW by 2003 and 6774 (19%) of this installed capacity is met by the coal plants. In 2003, the total amount of produced electricity was 140 billion kWh and 19% of this amount was obtained from the coal plants. Turkey has recently concentrated on natural gas for production of electricity. While the share of coal in production of electricity reached 50% in 1986, today natural gas has taken the place of coal. In other words, while Turkey was dependent on foreign countries for fulfilling 21% of its electricity production in 1986, it has become dependent on foreign countries for fulfilling 56% of its electricity production in 2003. Turkey can produce electricity using renewable energy resources, especially coal.

Vertical rock cutting rig (VRCR) suggested for performance prediction of roadheaders

Abstract This study demonstrates the roadheader performance prediction ability of previously developed vertical rock cutting rig (VRCR). Conical pick cutting tests were conducted on selected rock samples in both relieved and unrelieved cutting modes to determine the relationships between dependent and independent parameters in rock cutting and to investigate the optimum cutting condition. It was seen that relationships among dependent and independent variables match up with previous studies. Furthermore, two roadheader sites were visited, rock samples were collected and cutting rates of roadheaders were recorded. Rock cutting tests on these samples showed that performance prediction with VRCR is a plausible option.

A Comparative Study on the Energy Demand of Turkey: Coal or Natural Gas

Energy demand which has increased rapidly is estimated to increase also in the future. Coal and natural gas would continue to have primary role in electricity generation and industry. Turkeys energy consumption has been growing faster than its production. Natural gas is the greatest source in the energy consumption with a share of 32%. Lignite coal is major domestic energy source of Turkey and its reserves are 12.4 billion tons. Since most of the lignite reserves are low in quality, they are used mostly in electricity generation. On the other hand, Turkey has very limited natural gas reserves. Aim of this article is to evaluate the energy demand of Turkey based on hard coal, lignite and natural gas. As a result of the study it was determined that 70% of the primary energy consumption is met by imported energy sources. This figure shows that Turkeys dependency on foreign energy will continue to increase in following years in parallel with its economic growth. Turkey should increase the use of domestic sources, since foreign dependence of country can be minimized.

Rock Cutting Tests with a Simple-Shaped Chisel Pick to Provide Some Useful Data

Chisel-type hand crafts are one of the first hand tools of mankind. Additionally, they were used on early rock excavation machines as cutting tools when mechanical excavation machines had been newly developed. Since they had rather simpler geometrical shape, especially the simpleshaped ones, they provided a better understanding of rock cutting mechanism and led to the development of the rock cutting theories (Evans 1958; Potts and Shuttleworth 1959). Rock cutting tools are divided into two subgroups, namely drag picks and roller bits. Simple-shaped chisel picks belonged to drag picks group along with complex-shaped chisel picks, radial picks, forward attack picks and, conical picks as seen in Fig. 1. Simple chisel picks, nearly, have no practical usage on rock cutting machines. These tools are only used on cutter heads of some drilling machines operated in lowand medium-strength rocks. Radial and forward attack picks are used on partial face machines such as shear loaders, roadheaders, continuous miners, ploughs. Furthermore, complexshaped chisel picks are used on tunnel boring machines (TBM). Complex picks are utilized both with disc cutters in mixed face conditions and alone in soft-to-medium-strength rock formations (Bilgin et al. 2012). Regardless of their geometrical complexities, all types of chisel picks have identical cutting mechanism (Yasar 2017) and execution of cutting experimentswith a selected type can contribute useful data for practical conditions. Some experimental studies were published about simple-shaped chisel picks containing relationships between dependent (e.g. cutting force) and independent (e.g. cutting depth) parameters bydifferent authors indifferent papers (Barker 1964; Pomeroy and Brown 1968; Roxborough 1976; Roxborough et al. 1981). Furthermore, there is very limited study about other pick types such as forward attack, radial and complex-shaped chisel picks. This note aims to put together all experimental results in both unrelieved and relieved cutting with simple chisel picks, especially on a certain lithology,which is in this case igneous rocks to provide a better understanding of cutting mechanism of the selected rock type. Furthermore, these experimental results may be used for practical rock conditions. In this study, rock cutting tests were carried out on five igneous rock samples using a simple-shaped chisel pick. Cutting tests were realized in both relived and unrelieved cutting modes in vertical rock cutting rig (VRCR). Mean cutting force (FC), maximum cutting force (FC0), specific energy (SE), ratio of maximum cutting force to mean cutting force (FC0/FC), variation of specific energy with spacing-todepth ratio (s/d), and some other parameters are recorded and discussed. Furthermore, effect of uniaxial compressive strength and tensile strength on cutting force and specific energy was presentedwith special reference to cutting depth.

Core Cutting Test with Vertical Rock Cutting Rig (VRCR)

Roadheaders are frequently used machines in mining and tunnelling, and performance prediction of roadheaders is important for project economics and stability. Several methods were proposed so far for this purpose and, rock cutting tests are the best choice. Rock cutting tests are generally divided into two groups which are namely, full scale rock cutting tests and small scale rock cutting tests. These two tests have some superiorities and deficiencies over themselves. However, in many cases, where rock sampling becomes problematic, small scale rock cutting test (core cutting test) is preferred for performance prediction, since small block samples and core samples can be conducted to rock cutting testing. Common problem for rock cutting tests are that they can be found in very limited research centres. In this study, a new mobile rock cutting testing equipment, vertical rock cutting rig (VRCR) was introduced. Standard testing procedure was conducted on seven rock samples which were the part of a former study on cutting rocks with another small scale rock cutting test. Results showed that core cutting test can be realized successfully with VRCR with the validation of paired samples t-test.