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Öğe Correction to: Investigating the Accuracy of Specimen Shape for Point Load Index Test in Predicting the Uniaxial Compressive Strength for Rocks Using Regression Analysis and Machine Learning (Mining, Metallurgy & Exploration, (2023), 40, 6, (2107-2115), 10.1007/s42461-023-00865-4)(Springer Science and Business Media Deutschland GmbH, 2023) Akbay, DenizSome equations in Figure 1 were incorrect. In Figure 1a, instead of “L=0.5D,” it should be “L>0.5D.” In Figure 1b,1c,1d, instead of “0.3W=D=W,” it should be “0.3WÖğe EFFECTS OF THE COVID-19 PANDEMIC ON TURKISH NATURAL STONE INDUSTRY: A GREY FORECASTING MODEL(2022) Ekincioğlu, Gökhan; Akbay, Deniz; Aydemir, ErdalWhen the indicators in recent years are examined in the developing and renewed economic environment in Turkey, it is seen that the momentum of the natural stone industry and its share in total mining exports have increased steadily. However, the Covid-19 pandemic in 2020, which affected the whole world, also affected the Turkish natural industry. Within the scope of this study, the export values of the Turkish natural stone industry on a monthly and yearly basis were evaluated both before the pandemic and during the pandemic. Export figures for 2020 and 2021 were tried to be estimated using the Gray Forecast model. With the effect of the Covid-19 pandemic, natural stone export figures for 2020 fell behind 2019 in February, March, April and May. With the normalization process in June, July and Months, normalization started in export figures and exceeded the export values of 2019 in September, October, November and December. In 2020, which was entered with great hopes, it was not possible to reach the targeted figures this year due to the pandemic. In addition, Also, export values for 2020 and 2021 were predicted using a GM (1,1) grey forecasting model, which is a method frequently used in uncertainty cases. 2020 and 2021 export values were estimated by using the GM (1,1) gray forecasting model, which is a method frequently used in uncertainty situations. It has been seen that the model can be used reliably to predict natural stone export figures. In the following years, some assessments and recommendations have been made that may make the Turkish natural stone industry stronger in the following years on issues such as health management of crises and adaptation to the current situation if such outbreaks are replicated in the global world economy.Öğe Estimating the brittleness values of carbonated rocks with Shore, Schmidt, and Leeb hardness values(Springer, 2022) Akbay, Deniz; Ekincioglu, GokhanThere is not a defined standard method for determining the brittleness of rocks. Prediction of rock brittleness using rebound based hardness test methods is widely used in the characterization of rocks because they are non-destructive, inexpensive, and easy to apply. Rock surface hardness can also be used to predict the physical and mechanical properties of rocks. In this study, hardness values of 12 different carbonated rocks were determined on the same specimens using 3 different methods. C-2 type Shore Scleroscope, L-type Schmidt hammer, and Leeb hardness test device are rebound based hardness tests. The aim of the study is to determine the most suitable rebound hardness test method, that can be used to estimate the four different brittleness values recommended, by considering the compressive and tensile strength values in the literature. Relationships between the hardness values obtained using three different test methods and four different brittleness values were analyzed. It was observed that each method can be interchangeable. It was determined that the rebound based hardness tests could be used in predicting two of the four different brittleness values, which are widely used in the literature but cannot be used in estimating the other two. The strongest relationships were obtained from Leeb hardness values, followed by Shore hardness values and Schmidt hardness values, respectively. The best method to estimate the two brittleness indexes of rocks was determined as Leeb hardness. Besides, Shore hardness and Schmidt hardness methods also had strong relationships between the two brittleness indexes.Öğe Estimating the brittleness values of carbonated rocks with Shore, Schmidt, and Leeb hardness values (vol 81, 206, 2022)(Springer, 2022) Akbay, Deniz; Ekincioglu, Gokhan[Anstract Not Available]Öğe Estimating Uniaxial Compressive Strength of Sedimentary Rocks with Leeb Hardness Using Support Vector Machine Regression Analysis and Artificial Neural Networks(Gazi Univ, 2024) Ekincioğlu, Gökhan; Akbay, Deniz; Keser, SerkanUniaxial compressive strength (UCS) of rock materials is a rock property that should be determined for the design and stability of structures before underground and aboveground engineering projects. However, it is impossible to determine the properties of rocks such as UCS directly due to the lack of standardized sample preparation, necessary equipment, etc. In this case, the UCS of rocks is predicted by index test methods such as hardness, ultrasound velocity, etc. Determining the hardness of rocks is relatively more practical, fast, and inexpensive than other properties. In this study, the UCS of sedimentary rocks was predicted as a function of Leeb hardness using artificial neural network (ANN) and Support Vector Machine (SVM) regression analysis. With the proposed ANN and SVM regression models, it is aimed to obtain more accurate and faster prediction values. To better train the models created in the study, the number of data was increased by compiling data from the studies in the literature. The UCS values predicted by the models obtained with two different methods and the measured UCS values were statistically compared. It was proved that the models created with ANN and SVM regression can be used reliably in predicting UCS values.Öğe Evaluating the Effect of Diameter-to-Length Ratio in Point Load Index Test on Predicting Uniaxial Compressive Strength(2023) Akbay, DenizAccurate determination of the strength properties of rock materials is very important in engineering projects. The most important parameter used to express the strength of rocks is the uniaxial compressive strength (UCS). However, in some cases it can be quite difficult to determine the UCS. For example, when it is difficult to obtain rock specimens of the required size for UCS testing, indirect methods such as point load strength and ultrasonic wave velocity are used to estimate UCS. If the UCS is determined incorrectly, this can lead to irreversible design errors, project delays and financial losses. PLI testing is performed on specimens of different shapes as well as on specimens of different sizes. This study investigates the ability of the values obtained as a result of PLI tests on specimens prepared with different diameter/length (D/L) ratios to predict UCS. For this purpose, PLI experiments were performed on seven different carbonate rocks prepared at different D/L ratios. The relationships between the obtained values and the UCS values of the rocks were analyzed. High correlations were obtained between PLI and UCS values and it was observed that D/L ratio has no significant effect on UCS estimation.Öğe Farklı cihaz ve yöntemler ile belirlenen Shore sertlik değerlerinin karbonatlı kayaçların gevreklik değerlerinin tahmininde kullanılabilirliğinin incelenmesi(Pamukkale Üniversitesi, 2021) Akbay, Deniz; Ekincioğlu, Gökhan; Altindağ, Raşit; Şengün, NazmiYeraltı veya yer üstü mühendislik projeleri öncesinde kayaçların kesilebilirlik ve delinebilirlik özelliklerini etkileyen sertlik ve gevreklik değerlerinin belirlenmesi çok önemlidir. Kayaçların kesilebilirlik ve delinebilirlik özelliklerini belirlemek, bazı diğer fiziksel ve mekanik özelliklerini doğrudan belirlemek için uygulanan testler gibi pahalı ve zaman alıcı olabilmektedir. Kayaçların sertlik değerlerinin belirlemesi nispeten diğer özelliklerine göre daha ekonomik ve hızlı olmaktadır. Ayrıca sertlik değerleri, kayaçların fiziksel ve mekanik özelliklerinin tahmininde güvenilir bir şekilde kullanılabilmektedir. Bu çalışma kapsamında, 13 farklı karbonatlı kayacın Shore sertlik değerleri üç farklı cihaz (C-2 tipi Shore Scleroscope’u, dijital durometre ve dijital Shore sertliği ölçüm cihazı) kullanılarak aynı numuneler üzerinde belirlenmiştir. Elde edilen veriler sonucunda farklı ölçüm cihazlarının klasik yöntem yerine kullanılabilirliği araştırılmıştır. Ayrıca kazı mekaniği açısından önemli bir kayaç özelliği olan ve literatürde basınç ve çekme dayanımı değerleri dikkate alınarak önerilen dört farklı gevreklik değerinin tahmin edilmesinde kullanılabilecek en uygun yüzey sertliği ölçme yönteminin belirlenmesi amaçlanmıştır. Üç farklı cihazdan elde edilen Shore sertlik değerleriyle dört farklı gevreklik değeri arasındaki ilişkiler basit regresyon analizleri ile irdelenmiştir. Sonuç olarak dijital Shore sertliği ölçüm cihazlarının klasik C-2 tipi Shore Scleroscope’u yerine güvenli bir şekilde kullanılabileceği görülmüştür. Shore sertlik değerinin literatürde çokça kullanılan dört farklı gevreklik değerinden iki tanesini tahmin etmede güvenilir olduğu iki tanesini tahmin etmede ise kullanılamayacağı belirlenmiştirÖğe Investigating the Accuracy of Specimen Shape for Point Load Index Test in Predicting the Uniaxial Compressive Strength for Rocks Using Regression Analysis and Machine Learning(Springer Heidelberg, 2023) Akbay, DenizThe strength of rocks and soil is a crucial design parameter in engineering projects, and it can be determined through various test methods such as uniaxial compressive strength, tensile strength, and shear strength. The point load index test is a popular indirect test method for predicting the uniaxial compressive strength of rocks. However, the reliability of the point load index's estimation of uniaxial compressive strength of rocks is questioned due to the wide range of coefficients that are used to predict uniaxial compressive strength of rocks using point load index values. Factors such as the shape and type of rock specimen, practitioner, and test apparatus used can affect the accuracy of the point load index test. This study investigated the effect of four different specimen shapes used in point load index test (diametral, axial, block, and irregular lump tests) in predicting the uniaxial compressive strength. The rock samples were tested using four test procedures which are called diametral, axial, block, and irregular lump tests. The results showed that the irregular lump test was the most accurate in predicting uniaxial compressive strength, with the highest correlation coefficients and lowest mean absolute percentage errors. The point load index test can be used as a reliable predictor of uniaxial compressive strength of rocks when the irregular lump test is preferred.Öğe Investigation of the availability of a new point load test device in characterization of rocks(2021) Akbay, Deniz; Altındağ, RaşitDifficulties in determining rock properties have led to the developed and increased use of index test methods predicting them. Index test methods are mostly simple, cheap, and easy to apply but there are some restrictions due to these specifications. The most used method to determine the strength values of rocks indirectly is the point load index. The main aim of this study is primarily investigating the usability of modified test device instead of classical test device. For this, laboratory tests were carried out on rocks with different strength values (3 igneous, 1 metamorphic, 3 sedimentary). The point load index tests were carried on 15 different classical test devices and on a modified test device which the limitations of the classical test device were eliminated. Analysis of the obtained results was carried out by the simple regression method. It was determined the modified test device can be used reliably instead of the classical test devices. Besides, while determining the strength tests the stress distributions on the samples were examined with the finite element method.Öğe Point Load Index Applicability to Predicting Rocks' Uniaxial Compressive and Tensile Strengths: Available Data Analysis and FEM-Based Validity Check(Springer, 2024) Akbay, DenizIn projects that are in contact with rocks, it is very important to determine the strength parameters of the rock correctly. While there are several approaches to this, the experimental approach is the most recommended. The strength of the rocks is determined by laboratory experiments. However, these experiments can sometimes be complicated, time-consuming, expensive, or samples with the required size cannot be prepared. In such cases, index, simpler, and cheaper test methods can be used to estimate the strength values. Many studies have used point load index (PLI) to predict uniaxial compressive strength (UCS). This study investigated whether PLI predicts UCS or Brazilian tensile strength (BTS) better. A data set was created from the studies with UCS, BTS, and PLI values, which were determined using the same rock samples in the literature. The finite element approach was used to analyze the stress distributions on the samples to explain better the results obtained. As a result, it was seen that PLI can be used reliably in magmatic and metamorphic rocks to predict both UCS and BTS. It was determined that PLI predicted BTS better and that the stress distributions formed on the sample at the time of the experiment were very similar to those of the BTS test.Öğe SUGGESTING CONVERSION FACTOR COEFFICIENTS for ESTIMATING DIFFERENT TYPES of SCHMIDT HAMMER REBOUND HARDNESS VALUES(2023) Akbay, Deniz; Ekincioğlu, GökhanMechanical properties of rocks such as uniaxial compressive strength, tensile strength, shear strength are the properties that determine their behavior under load. These properties of rocks are often determined by difficult, complex, time-consuming and expensive test methods. Therefore, instead of determining these properties directly, these properties can be estimated indirectly by using relatively inexpensive, fast and easily applicable methods. The surface hardness parameter of Schmidt hammer rebound hardness is fast, inexpensive, and easy to apply to determine the hardness of rocks and concrete. It is also used to indirectly determine the mechanical properties of rocks. It is seen that two different types of hammers (N-type and L-type) with different impact energies are commonly used in the literature. In this study the correlations between the surface hardness of different rocks obtained using N-type and L-type Schmidt hammers were analyzed. For this purpose, data were compiled from studies in the literature, which included both N-type and L-type Schmidt hammer rebound hardness of different rock types, and the collected data were analyzed statistically. Coefficients have been proposed for the conversion of N-type and L-type Schmidt hammer rebound hardness to each other.Öğe The effect of non-standard loading platen usage on point load index value of rocks(South African Institute of Mining and Metallurgy, 2021) Akbay, Deniz; Altındağ, RaşitThe point load index is a simple, fast, and inexpensive method for determining rock strength and can be applied both in the field and in the laboratory. There are, however, some disadvantages and limitations to the method, and the test results can be affected by the person carrying out the test, the rock characteristics, or the test device. In this study we describe an investigation into how the point load index value is affected by the shape of the conical platens used in the test. Point load index tests were carried out using different devices fitted with conical platens of different spherical radii, and on a modified device which circumvented the limitations/disadvantages. It was seen that the point load index value increased as the platen radius increased, as expected. In the case of testing using non-standard conical platens, an equation is proposed to normalize the point load index value with respect to the standard spherical radius value.Öğe THE EFFECT OF SAMPLE SIZE ON THE FLEXURAL STRENGTH OF SEDİMENTARY CARBONATE ROCKS UNDER CONCENTRATED LOAD(2021) Akbay, Deniz; Şengün, Nazmi; Altındağ, Raşit; Ekincioğlu, GökhanFlexural strength is an important mechanical property used in the selection of the application area of natural building stones. The flexural strength of natural stones in our country is determined according to the test standards prepared by the European Union. According to TS EN 12372, the recommended test sample dimensions for the determination of the flexural strength of natural stones are 50×50×300 mm. However, generally, 20-30 mm thick plates are used in flooring, cladding, and exterior applications in buildings. In practice, 50 mm thick plates are rarely used, as well as preparing 50 mm thick test samples is a laborious and time-consuming process. In this study, it has been investigated how much the sample size affects the flexural strength of sedimentary carbonate rocks when using test samples prepared in two different sizes. It has been observed that the flexural strength values obtained from the test samples prepared in different sizes of the same rock are very close to each other. Besides, the stress distributions formed on the rock sample were analyzed with ANSYS Workbench 2020 R1. It has been determined that the stress distributions in the samples prepared in different sizes, exposed to the same load, occur in the same regions, and concentrate.Öğe Usability of Digital Shore Hardness Devices in Estimation of Physical and Mechanical Properties of Rocks(Springer, 2021) Akbay, Deniz; Ekincioğlu, GökhanIn this study, the Shore hardness measurements are made on carbonate rocks using Durometer PCE-1000, Mitech MH310 Hardness Tester and C-2 type Shore Scleroscope, and the results obtained were compared. The usability of digital new generation Shore hardness test devices (Durometer PCE-1000 and Mitech MH310 Hardness Tester) to determine the Shore hardness of the rocks is investigated.
