Sürdürülebilir Kalkınma Amaçları
Yayınlar
- MakaleAçık Erişim2026Variability of Schmidt Rebound Values in Volcanic Rocks (Basalt and Lapilli Tuff): Comparative Effect of Surface Roughness, Alteration, and Testing Methods
Karaman, Kadir; Külekçi, Gökhan; Çakır, Yaşar; Kolaylı, Hasan
Enhancing the sustainability and safety of rock engineering requires understanding how micro-structural and alteration conditions influence the geomechanical properties of rocks in geotechnical projects. The determination of surface hardness using the Schmidt Hammer is an interdisciplinary experimental method employed in mining, geology, and civil engineering. This study quantitatively evaluates the effects of surface roughness, weathering degree, and evaluation procedures on Schmidt rebound values obtained from basalt and lapilli tuff. Field measurements on eight surfaces produced rebound values between 10 and 60, with standard deviations ranging from 2.4 to 11, reflecting substantial variability related to roughness and alteration. Laboratory results showed that cut surfaces yielded the highest hardness values (Mean ≈ 57–58) with very low variability (SD ≈ 1.1–1.6), whereas natural surfaces exhibited markedly lower rebound values (Mean ≈ 19–22) and greater scatter (SD ≈ 4–4.5). A strong correlation (R2 > 0.97) was observed between JRC roughness and rebound values in laboratory-prepared samples. The percentage difference among the USBR, ASTM, and Sumner & Nel methods remained below 5% when the standard deviation of measurements was under 2, indicating that method selection becomes critical only for heterogeneous surfaces. Mineralogical heterogeneity further increased variability in lapilli tuff, whereas basalt provided highly consistent responses. Overall, this study introduces quantitative thresholds linking roughness, weathering, and statistical variability, offering a more rigorous and reproducible framework for interpreting Schmidt hardness measurements.
- MakaleYalnız künye2026Variable-speed retrofit of a legacy slurry pumping duty: Measured energy reduction with proxy-based operability assessment
Külekçi, Gökhan; Aygün, Muhammet; Göller, Zafer; Yildiz, Onur
Legacy ore beneficiation plants often operate slurry pumps at fixed speed despite variable sump inflow and slurry conditions, which can increase electricity demand and complicate level control. This study evaluates a variable-speed retrofit in which a variable frequency drive was integrated with level feedback and proportional-integral control for a legacy slurry pumping duty. Measured average operating power decreased from 25.6 kW before retrofit to 11.6 kW after implementation, documenting a substantial reduction in electrical demand under the observed operating regime. Because hydraulic-duty data were unavailable for both periods, this result is not presented as a duty-normalised specific-energy reduction. Process interpretation was supported by a bounded proxy framework based on a flowsheet-consistent solids band over 177 days. The proxy analysis linked solids variability to derived slurry density behaviour and operability implications. Overall, the study documents measured electrical-demand reduction and provides a framework for discussing retrofit performance where plant instrumentation is limited.
- MakaleYalnız künye2025First evaluation and ecological risk of potentially toxic elements in the formations of Akçakale cave (Gümüşhane-NE-Türkiye)
Saydam Eker, Çiğdem; Külekçi, Gökhan; Uçak, Gül
In this study, the potential toxic element levels (PTEs) and adverse health effects of Akçakale cave formations were evaluated using geochemical parameters such as enrichment factor (EF), geo-accumulation index (Igeo), contamination factor (CF), ecological risk factor (Eri), potential ecological risk index (PERI), and non-carcinogenic hazard index (HI). Water does not pose a pollution risk, as the concentrations of potentially toxic elements in all samples are within the permissible limits for drinking water. According to the calculated geochemical parameters, all the samples were polluted with As, Co, Ni, Cu, V, and Pb. Ni, As, Cu, and Pb show very high ecological risk (PER > 320) in all samples, except Cu and Pb in T2T. The PERI values of the PTEs were more than 600 in all samples, indicating a very high potential ecological risk. The HI > 1 values for Co and As in all samples for both adults and children suggested potential non-carcinogenic health risks from exposure to these elements in the cave environment. The PTEs in the Akçakale cave formation were most likely linked to lithogenic, geogenic (Pb–Zn-Cu mineralization), and anthropogenic (agricultural activities) processes, per the findings of the data analysis using multivariate statistics (PCA and PCC). These data obtained are the first findings regarding the potential toxic element content of Akçakale cave.
- MakaleAçık Erişim2025Enhancing mineral processing with deep learning: Automated quartz identification using thin section images
Külekçi, Gökhan; Hacıefendioğlu, Kemal; Başağa, Hasan Basri
The precise identification of quartz minerals is crucial in mineralogy and geology due to their widespread occurrence and industrial significance. Traditional methods of quartz identification in thin sections are labor-intensive and require significant expertise, often complicated by the coexistence of other minerals. This study presents a novel approach leveraging deep learning techniques combined with hyperspectral imaging to automate the identification process of quartz minerals. The utilizied four advanced deep learning models—PSPNet, U-Net, FPN, and LinkNet—has significant advancements in efficiency and accuracy. Among these models, PSPNet exhibited superior performance, achieving the highest intersection over union (IoU) scores and demonstrating exceptional reliability in segmenting quartz minerals, even in complex scenarios. The study involved a comprehensive dataset of 120 thin sections, encompassing 2470 hyperspectral images prepared from 20 rock samples. Expert-reviewed masks were used for model training, ensuring robust segmentation results. This automated approach not only expedites the recognition process but also enhances reliability, providing a valuable tool for geologists and advancing the field of mineralogical analysis.
- MakaleAçık Erişim2024Çevresel Tehlikelerin Belirlenmesi ve Sağlık Etkilerinin İncelenmesi: Gümüşhane Katı Atık Tesisi Örneği
Güvendi, Aslıhan; Külekçi, Gökhan
Bu çalışmada, Gümüşhane ilindeki katı atık tesisinin iş sağlığı ve güvenliği Elmeri yöntemi kullanılarak incelenmiştir. Katı atık yönetim süreci, atık toplama, taşıma, ayrıştırma, geri dönüşüm ve bertaraf gibi adımları içermektedir. Bu süreçlerde potansiyel olarak ortaya çıkabilecek; atık toplama sürecinde, keskin kenarlı ve delici maddelerin bulunmasıyla oluşabilecek kesilmeler ve delinmeler, atıkların taşınması sırasında ağır yüklerin kaldırılmasıyla ilgili bel ve sırt yaralanmaları, ayrıştırma işlemi sırasında kimyasal maddelerin sızması veya bu maddelerin solunmasıyla ilgili zehirlenme veya solunum yolu rahatsızlıkları, geri dönüşüm sürecinde kullanılan makinelerin veya ekipmanların yanlış kullanımıyla ilgili kırılma, ezilme veya yakma gibi kazalar, atıkların bertaraf edilmesi sırasında oluşabilecek patlama veya yangın riskleri gibi tehlikeler mevcuttur. Bu tehlikeler, Elmeri yöntemi kullanılarak tanımlanmış, çalışanların ve çevrenin bu tehlikelere maruz kalma düzeyi değerlendirilmiş ve ortaya çıkan riskler belirlenmiştir. Elde edilen sonuçlar, tesis yöneticileri ve ilgili paydaşlar için önemli bir kaynak olabilir ve katı atık yönetiminde daha etkili önlemlerin alınmasına yardımcı olabilir. Bu çalışma kapsamında Elmeri yönteminde belirtilen 7 ana başlık altında toplanan metotlara göre çalışma alanlarında toplam 494 adet gözlem yapılmıştır. Yapılan gözlemlerden 239 tanesi doğru güvenlik davranışı ve durumları belirtirken 255 tanesi yanlış güvenlik davranış ve durumlarını belirtmektedir. Gözlem sonuçlarına göre çalışma alanlarındaki en yüksek mevcut güvenlik endeksi % 57,2 ile atık toplama gündüz vardiyası, en düşük indeks ise % 29,3 ile atık ayrıştırma kısmında hesaplanmıştır.
- MakaleAçık Erişim2024Performance of different fibre types in alkaline-activated concrete produced with industrial wastes: volcanic rock powder and blast furnace slag
Aksüt, Yavuz Selim; Külekçi, Gökhan; Çullu, Mustafa; Yetgin, Şükrü
The objective of the study is to determine the effects of different fibre types and ratios on the mechanical and physical properties of alkali-activated concrete (AAC) and to optimise important properties such as workability, unit weight, water absorption, compressive strength, modulus of elasticity and abrasion resistance of these concretes. Concrete samples were produced using steel and polyester fibres at ratios of 0.25%, 0.50%, 0.75% and 1%. The fibre ratios were varied, and various tests were conducted to determine the mechanical and physical properties of the concrete samples. The experiments clearly revealed the effects of fibre types and ratios on the performance of concrete. These results clearly demonstrate the effects of different fibre types and ratios on the mechanical and physical properties of AACs. Particularly noteworthy is the water-retaining property of polyester fibres, their effect on workability and their enhancing effect on abrasion resistance. The effects of steel fibres on compressive strength and modulus of elasticity are more pronounced, but they may present disadvantages in terms of workability and abrasion resistance. It is observed that mixed fibre usage provides a good balance in some properties. This study provides a roadmap for evaluating sustainable material options in the concrete industry and guiding future research.
- MakaleYalnız künye2022Investigation of usability of building rubble as road underfill
Külekçi, Gökhan; Osman Yilmaz, Ali
For resources to be used efficiently, the structures built on the earth must be long-lasting. The longevity of the roads built with a length of millions of kilometers per year is determined by the nature of the filling material, traffic, equivalent axle load, climatic effects, material fatigue, and layer thicknesses used. The fact that filling material complies with the standards and is easily available will ensure that the road construction works are both economical and long-lasting. Many building rubbles are formed from the buildings that have completed their lives in the urban transformation process. Storage and disposal of this building's rubble are very difficult. To eliminate these difficulties, the usage areas of the rubble should be increased. In this study, some mechanical experiments were carried out on the building rubble obtained from the Black Sea region, and these were interpreted. Grain density, freeze-thaw tests, Micro-Deval, and Determination of Fragmentation Resistance, tests were carried out according to TSE and ASTM standards of aggregates obtained from building rubble. The results obtained from the experiments were compared with the technical specifications of the General Directorate of Highways. It has been revealed that the analyzed aggregate can be used as road fill in highways.
- MakaleYalnız künye2022Assessment of excavability classification in a Limestone Quarry: A case study from Bayburt, Turkey
Külekçi, Gökhan; Vural, Alaaddin; Aliyazicioğlu, Şener
Excavability is a measure of material which can be excavated with classical excavation equipment. Studies to decide the rock excavability characteristics contribute to the suitability of engineering projects. In this study, a limestone quarry (in Bayburt, Turkey) was analysed with excavability classification systems and appropriate systems were determined. To accomplish this aim, point load index and Schmidt hardness tests were practiced and changed to uniaxial compressive strength tests. After that, findings were categorized with classification systems in excavation and matched against practices from field. In this study, rock mass was addressed as “pre-explosion”, “hard ripping” and “hammer and blasting” in accordance with distinctive classification systems. All determined as rock mass should be blasted for loosening then dug with hydraulic breakers. This practice is totally compatible with in-site excavations fulfilled. According to study results, the most suitable parameters to decide surface excavational classification are load strength index, geological strength index and the degree of rock mass weathering
- MakaleAçık Erişim2022Investigation of gamma ray absorption levels of composites produced from copper mine tailings, fly ash, and brick dust
Külekçi, Gökhan
To date, heavyweight concretes have been produced from various heavy aggregates as radiation insulation materials, and their gamma ray absorption levels have been investigated. Many of the studies have used heavy aggregates instead of cement or coarse aggregates from composite material components. The present study prepared lightweight concretes using copper mine tailings, clay brick dust, and fly ash instead of fine aggregates. Some mechanical tests (density, compressive strength, and ultrasonic pulse velocity) were performed on composite blocks with dimensions of 5*5*5 cm, and radiation interaction parameters [linear absorption coefficient (cm−1), mass attenuation coefficient (cm2/gr), HVL (half-value layer) (cm), MFP (cm), and permeability (%)] were measured. Radiation interaction parameters were obtained using a HPGe gamma detector. Radiation measurements were performed at five different photon energies: 583 keV (133Ba), 609 keV (133Ba), 662 keV (137Cs), 911 keV (133Ba), 1173 keV (60Co), and 1332 keV (60Co). Additionally, the compressive strength and UPV values of composite materials were associated with their gamma ray permeability. Tests revealed that samples with the addition of copper mine tailings yielded the best energy absorption at all energy levels and that absorption decreased as the energy level increased. For example, with the increasing of the energy level, mass attenuation coefficients decreased. The highest mass attenuation coefficients were obtained as 0.128 cm2/g at an energy level of 583 keV in composites produced from copper mine tailings. On the other hand, it was measured at the same energy level as 0.069 cm2/g (a 46% decrease) in the composites produced with fly ash. In addition, it was observed that fly ash used as a fine aggregate did not have a significant effect on mass attenuation coefficient and could be used as a gamma shield if the material thickness was increased to an average of 14 cm. This study revealed that tailings materials could be used as radiation shields. This study also demonstrated that not using heavy aggregates and producing lightweight concrete in radiation shield production significantly reduced shield production cost.
- MakaleAçık Erişim2021⁶⁰Co Radyoaktif Nokta Kaynaği ile Uçucu Külün Gama Radyasyon Koruma Özellikleri
Külekçi, Gökhan
Gelişmekte olan beton teknolojisi sayesinde hafif beton ve uçucu kül betonla ilgili birçok alanda kullanılabilmektedir. Dünyanın güncel sorunlarından olan radyasyondan, korunmak için birçok araştırmacı uçucu külü kullanmış fakat çok az sayıda araştırmacı hafif beton üzerinde çalışmıştır. Radyasyonun etkilerinden korunmak için araştırmacılar ağır beton ve ağır agregalar kullanılarak gama ışını soğurma miktarlarını incelenmiştir. Bu çalışmada c sınıfı uçucu kül, çimento yerine %30-50-100 dozajlarında kullanılarak 3 farklı hafif beton hazırlanmıştır. 50*50*50 mm boyutlarında hazırlanan kompozit bloklar üzerinde yoğunluk ve basınç dayanımı deneyleri yapılmış, doğrusal zayıflama katsayısı (cm-1), kütle zayıflama katsayısı (MAC) ve onuncu katman değeri (TVL) (cm) gibi radyasyon etkileşim parametreleri ölçülmüştür. Radyasyon etkileşim parametreleri HP Ge gama dedektörü kullanılarak elde edilmiştir. Radyasyon ölçümleri için 1173 keV (⁶⁰Co) ve 1332 keV (⁶⁰Co) olarak 2 farklı foton enerjisi kullanılmıştır. Yapılan çalışmalar sonucunda uçucu kül içeriği arttıkça basınç dayanımının azaldığı, hazırlanan kompozitlerinden %100 uçucu kül içeren örneklerin basınç dayanımının en az olduğu, uçucu kül miktarı düştükçe yoğunluğun arttığı belirlenmiştir. Hazırlanan kompozitlerde enerji seviyeleri arttıkça doğrusal zayıflama katsayısı arttığı görülmüştür. Bu çalışma sayesinde birçok alanda kullanılan uçucu küllerin radyasyon kalkanı olarak kullanılabileceği ortaya konmuştur. Ayrıca bu çalışma ile radyasyon kalkanı üretiminde, ağır agrega kullanılmaması ve hafif beton üretilmesi nedeni ile kalkan üretim maliyeti önemli derecede düşecektir
- MakaleAçık Erişim2021The effect of pozzolans and mineral wastes on alkali-silica reaction in recycled aggregated mortar
Külekçi, Gökhan
In this study, it was aimed to examine recycled aggregates (RA), which are considered as aggregates, in terms of alkali-silica reaction (ASR) before being used in concrete, to determine the risk status and to reduce the ASR value. In order to reduce and stop the ASR, the cement was replaced with clay brick and fly-ash by 10–40 %. Marble waste and Pb-Zn mine waste were used instead of RA in order to reduce aggregate reactivity. At the end of 28 days, compared to the control sample, it was observed that mortar bar samples containing tailings instead of fine RA has 18 % less expansion and marble waste (MW) added samples again instead of fine RA has 34 % less expansion. Furthermore, 40 % fly ash (FA) added samples decreased the level of ASR for 96 %, and in 10 % clay brick mixed samples ASR formation is decreased to 85 %. As a result, recycled aggregates were determined to be reactive for ASR. It has been determined that marble and lead-zinc mine facility wastes added as replace with to RA reduce the expansion effect by ASR in the cement paste. With this study, it has contributed to the safe use of the increasing use of RA in the world.
- MakaleAçık Erişim2021Comparison of field and laboratory result of fiber reinforced shotcrete application
Külekçi, Gökhan
Synthetic fibers, which have become one of the main components of shotcrete, have been studied by many researchers in the laboratory environment. Unfortunately, the results obtained as a result of these researches are not suitable for underground chimneys due to the differences in ambient conditions and application differences. In this study, it is aimed to compare the results of the experiment samples prepared and kept in the laboratory with the mechanical properties of the shotcrete applied in underground conditions. For this purpose, keeping the slump and cement proportions constant, 35 cubic samples were prepared using 2 and 6 kg synthetic fiber for 1 m3 in the laboratory, and 30 cylinder samples and 6 plate samples were prepared for underground. While mechanical experiments were carried out on prepared cube and cylinder samples, the EFNARC plate test and freeze-thaw test were carried out on plate samples. It was observed that the set accelerator made a significant increase in resistance at the end of the 28 days and that the resistance of the samples prepared with polyester fibers in the laboratory environment were very high. As a result of the EFNARC panel tests performed, it was determined that the energy absorption of synthetic fibers increased with fiber amount. Thanks to this study, the energy absorption of the synthetic fiber used has been measured, and the reliability and practicality of the experiments carried out in the laboratory have been increased by evaluating the field conditions and laboratory conditions.
- MakaleYalnız künye2014Assessment of strength properties of cemented paste backfill by ultrasonic pulse velocity test
Yilmaz, Tekin; Ercikdi, Bayram; Karaman, Kadir; Külekçi, Gökhan
Ultrasonic pulse velocity (UPV) test is one of the most popular non-destructive techniques used in the assessment of the mechanical properties of concrete or rock materials. In this study, the effects of binder type/dosage, water to cement ratio (w/c) and fines content (<20 μm) of the tailings on ultrasonic pulse velocity (UPV) of cemented paste backfill (CPB) samples were investigated and correlated with the corresponding unconfined compressive strength (UCS) data. A total of 96 CPB samples prepared at different mixture properties were subjected to the UPV and UCS tests at 7, 14, 28 and 56-days of curing periods. UPV and UCS of CPB samples of ordinary Portland cement (CEM I 42.5 R) and sulphate resistant cement (SRC 32.5) initially increased rapidly, but, slowed down after 14 days. However, UPV and UCS of CPB samples of the blast furnace slag cement (CEM III/A 42.5 N) steadily increased between 7 and 56 days. Increasing binder dosage or reducing w/c ratio and fines content (<20 μm) increased the UCS and UPV of CPB samples. UPV was found to be particularly sensitive to fines content. UCS data were correlated with the corresponding UPV data. A linear relation appeared to exist between the UCS and UPV of CPB samples. These findings have demonstrated that the UPV test can be reliably used for the estimation of the strength of CPB samples.