Browsing by Author "Akin, Mutluhan"

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3-Boyutlu Kaya Düşme Analizlerinde Geri Verme Katsayısı Etkisinin İncelenmesi
(2025) Uykun, İbrahim; Akin, Mutluhan; Varol, Ogün Ozan
Türkiye, jeolojik, jeomorfolojik ve iklim özellikleri nedeniyle bulunduğu coğrafyada doğal afetler sık yaşanmakta ve bu afetler arasında kaya düşmeleri, ülkenin pek çok bölgesinde ciddi can ve mal kayıplarına yol açmaktadır. Kaya düşme modelleme çalışmalarında girdi parametresi olarak kullanılan normal (Rn) ve tanjant (Rt) arazi geri verme katsayıları, blokların kinetik enerjisi ve hızıyla birlikte yuvarlanma mesafelerini belirleyen temel parametrelerdir. Bu katsayılar, kaya düşme analizlerinde bloğun yamaç yüzeyine çarpma esnasındaki enerji ve hız kayıplarını belirler, böylece modelde bloğun nasıl bir yörünge ve hareket dinamiği izleyeceğini ortaya koymaktadır. Geri verme katsayıları, arazi deneyleri (blok düşürme) veya kaya düşmelerinin yaşandığı sahalardaki daha önce düşen blokların konumları üzerinden geriye dönük analizlerle belirlenebilmekte veya arazi deneyleri ve geriye dönük analizlerin uygulanamadığı alanlarda, benzer litolojilere sahip veya yakın bölgeler için daha önceki bilimsel çalışmalarda kullanılan verilerden yararlanılabilmektedir. Bu çalışma kapsamında, kaya düşme modellemelerinde yapılan analizlerde farklı yöntemler kullanılarak belirlenebilen ve analizler için önemli bir parametre olan arazi geri verme katsayılarının (Rn ve Rt) yuvarlanma hattı, sıçrama yüksekliği, kinetik enerji ve yanal saçılım gibi unsurlar üzerindeki etkileri incelenmiştir. Yapılan çalışmada, gerçek bir sayısal yüzey modeli kullanılarak 3-boyutlu kaya düşme simülasyonları gerçekleştirilmiş ve yapılan analizlerde Rn ve Rt katsayılarının değerleri belirli sınırlar arasında değiştirilerek parametreler üzerindeki etkisi belirlenmiştir. Yapılan çalışma sonucunda, Rn ve Rt arazi geri verme katsayılarındaki değişimlerin tüm parametrelerde farklı oranlarda değişikliğe neden olduğu ve analiz sonuçlarının karşılaştırılması ile Rt katsayısının Rn katsayısına kıyasla parametreler üzerinde daha etkili olduğu veri setleri ve dağılım grafikleri ile ortaya konmuştur. Rt katsayısının değerinin artması ile özellikle 0,5 değerinden itibaren yuvarlanma mesafesi ve yanal saçılımlar da önemli değişiklikler belirlenmiştir.
A Comparative Slope Stability Analyses of Heavily Jointed Open-Pit Slopes Using 3d Limit Equilibrium and Finite Element Methods: a Case Study From Bingöl, Türkiye
(Taylor & Francis Ltd, 2024) Varol, Ogun Ozan; Ayhan, Mustafa; Akin, Mutluhan
This study investigates the slope stability of Bing & ouml;l open-pit iron mine slopes using 3D limit equilibrium and finite element methods. The pit benches are 3 m wide and 6 m high, with an overall slope angle of 38 degrees. The geological composition comprises slightly to moderately weathered and heavily jointed phyllite, micaschist, and gneiss. Shear strength parameters were determined through back analyses of already failed sections using the Hoek-Brown failure criterion and Geological Strength Index (GSI). Factor of safety values for static and dynamic conditions were calculated using 3D limit equilibrium and 2D finite element analyses. Results show good agreement between the two methods, with benches in the northern section exhibiting a significant decrease in safety factor under dynamic conditions, indicating near-limit equilibrium slopes.
A Comparative Study on Rockfall Block Motion Characteristics Using 3-D and 2-D Rockfall Simulations: a Case Study From Cappadocia (Mazı, Türkiye)
(Springer, 2025) Akin, Mutluhan; Dincer, Ismail; Orhan, Ahmet; Varol, Oguen Ozan
Within the scope of this research, rockfalls in Maz & imath; village of & Uuml;rg & uuml;p (T & uuml;rkiye) district were simulated on a digital surface model constructed using high resolution (2.9 cm) point cloud data retrieved from a real orthophoto mosaic gathered by an unmanned aerial vehicle in order to compare the results of 2-D and 3-D rockfall models. At the initial stage, 3-dimensional rockfall analyses were carried out using RocPro3D software and block dynamics such as trajectory, maximum runout distance, bounce height and total kinetic energy of the blocks were determined. Subsequently, a total of eight slope profiles were obtained from the point cloud data and 2-dimensional rockfall analyses were executed by means of RocFall 2-D software. Using a rockfall point source indicating the starting position of 2-D rockfall analysis, the rockfall analyses were repeated on 3-dimensional digital surface model and the block motion characteristics obtained from 2-D and 3-D analyses were compared. Eventually, it is revealed that block runout distances may differ in 3-D and 2-D rockfall analyses. Additionally, 3-D analyses reveal a significant advantage over 2-D analyses in terms of including topographic roughness, curves and obstacles in the model. On the other hand, one of the most significant variances between 2-D and 3-D rockfall analyses retrieved in this research is in the bounce height values. While the bounce height value in 2-D models may attain a maximum of 7 m, 3-D simulations point out that the detached blocks mostly roll over the slope with very low bouncing. When the simulation results are evaluated in terms of total kinetic energy, it is concluded that kinetic energy values are commonly higher in 2-D rockfall analyses than those of 3-D simulations. Conversely, block translational velocity values are typically comparable in both 2-D and 3-D rockfall models. Besides, considering the trajectories obtained via 3-D rockfall models for the study site, it is obvious that the settlement is under the risk of rockfall to a significant extent. Rockfall simulations highlight that the total kinetic energy values of the blocks are also quite high, which increase the destructive effect of rockfalls.
Comparison of Spt and Vs-Based Liquefaction Analyses: a Case Study in Ercis (Van, Turkey)
(Springer international Publishing Ag, 2018) Akkaya, Ismail; Ozvan, Ali; Akin, Mutluhan; Akin, Muge K.; Ovun, Ugur
Liquefaction which is one of the most destructive ground deformations occurs during an earthquake in saturated or partially saturated silty and sandy soils, which may cause serious damages such as settlement and tilting of structures due to shear strength loss of soils. Standard (SPT) and cone (CPT) penetration tests as well as the shear wave velocity (V-s)-based methods are commonly used for the determination of liquefaction potential. In this research, it was aimed to compare the SPT and V-s-based liquefaction analysis methods by generating different earthquake scenarios. Accordingly, the Ercis residential area, which was mostly affected by the 2011 Van earthquake (M-w = 7.1), was chosen as the model site. Ercis (Van, Turkey) and its surroundings settle on an alluvial plain which consists of silty and sandy layers with shallow groundwater level. Moreover, Caldiran, Ercis-Kocapinar and Van Fault Zones are the major seismic sources of the region which have a significant potential of producing large magnitude earthquakes. After liquefaction assessments, the liquefaction potential in the western part of the region and in the coastal regions nearby the Lake Van is found to be higher than the other locations. Thus, it can be stated that the soil tightness and groundwater level dominantly control the liquefaction potential. In addition, the lateral spreading and sand boiling spots observed after the 23rd October 2011 Van earthquake overlap the scenario boundaries predicted in this study. Eventually, the use of V-s-based liquefaction analysis in collaboration with the SPT results is quite advantageous to assess the rate of liquefaction in a specific area.
Evaluation of Liquefaction in Karasu River Floodplain After the October 23, 2011, Van (Turkey) Earthquake
(Springer, 2013) Akin, Mutluhan; Ozvan, Ali; Akin, Muge K.; Topal, Tamer
The eastern shore of Lake Van was shaken by a powerful earthquake (M (w) 7.2) on October 23, 2011. The epicenter of the earthquake was located at about 30 km north of the Van Province, which is one of the main cities in the Eastern Anatolia. The Van Province and particularly its largest district Ercis were adversely affected by the earthquake, and unfortunately, a total of 600 people lost their lives. Besides severe constructional damages and building collapses, ground deformations were widespread at many locations nearby the Lake Van and Karasu River floodplain. Numerous sand boils and lateral spreading cracks were observed at the left and right embankments of the Karasu River, which is one of the major streams in the region. In this study, field observations on liquefaction and lateral spreading features triggered by the M (w) 7.2 Van earthquake are initially presented. Then, the results of subsurface investigations including trial pits, drillings and geophysical surveys on specific large-scale sand boils are explained. Subsequently, liquefaction back-analysis is performed considering the gathered subsurface data. The analysis indicates that the liquefaction occurred in a shallow zone with approximately 4 m thickness in the investigated area. The Liquefaction Potential Index method reveals high liquefaction potential for the analyzed sand boil location. In addition, the effect of cap soil thickness on liquefaction is once more validated by this case.
Evaluation of the Physico-Mechanical Parameters Affecting the Deterioration Rate of Ahlat Ignimbrites (Bitlis, Turkey)
(Springer, 2017) Akin, Mutluhan; Ozvan, Ali; Dincer, Ismail; Topal, Tamer
The paper principally focuses on the durability assessment of various stratigraphic levels of Ahlat ignimbrites collected from the eastern region of Turkey. A total of four different ignimbrite types with dissimilar color, texture and particularly welding degree were tested in laboratory. The laboratory tests performed on the ignimbrite specimens indicate that the welding degree as well as the lithic material content mainly controls the strength and capillarity properties of the ignimbrites. In addition, the durability of highly porous ignimbrites strongly depends upon the degree of welding. The effect of several weathering agents on the ignimbrites was evaluated on the basis of decay constant parameter. Accordingly, salt and ice crystallization pressures are a couple of major destructive agents acting within the micropores of the ignimbrites. Conversely, the investigated specimens are relatively durable against cyclic wetting-drying. Statistical evaluations reveal that the pore diameter is the major controlling factor on the deterioration rate of the ignimbrites after specifically recurrent freeze-thaw cycles. Moreover, the dry unit weight of the ignimbrites is more significant than the uniaxial compressive strength considering the deterioration rates during wetting-drying and salt crystallization. A less significant relationship was obtained between pore diameter and salt crystallization decay constant.
Experimental Studies on Ignimbrite and the Effect of Lichens and Capillarity on the Deterioration of Seljuk Gravestones
(Elsevier, 2015) Ozvan, Ali; Dincer, Ismail; Akin, Mutluhan; Oyan, Vural; Tapan, Mucip
Ignimbrites are used extensively in masonry and decorative cladding not only in historical structures, but also in residential houses recently as well as monuments around Ahlat (Bitlis-Turkey) region because of their light weight, softness and insulating properties. The most famous architectural monument is the Ahlat Seljuk Tombs, in which ignimbrites were used for the structure. These are thousand year old gravestones that have been subjected to significant degradation over time caused by many physical and chemical effects. The aim of this study is revealing the mineralogical, petrographical, petrophysical and mechanical properties of fresh ignimbrites as well as determining the effect of lichens and capillarity on the deterioration of Seljuk gravestones in accordance with laboratory studies and field observations. A total of four different ignimbrite levels have been evaluated, which are widespread in the region and named as N1 (reddish brown), N2 (dark brown), N3 (yellowish gray) and N4 (black), respectively. Among these ignimbrites, the samples of N1 and N2 were employed in the construction of Seljuk gravestones. The lithic material content and welding degree are the main controlling factors of the engineering properties of ignimbrites. Laboratory test results indicate that high porosity of ignimbrites and transport of water mediated by capillarity accelerate the deterioration of ignimbrites. Furthermore, lichens play a preventive role in the deterioration mechanism of ignimbrites rather than disintegrating the tombstones. (C) 2014 Elsevier B.V. All rights reserved.
İgnimbiritlerdeki Kılcal Su Emme Özelliğinin Ahlat Selçuklu Mezar Taşlarının Bozunmasındaki Rolü
(2016) Oyan, Vural; Özvan, Ali; Tapan, Mücip; Akin, Mutluhan; Dinçer, İsmail
Selçuklular dönemine ait Ahlat Selçuklu mezar taşları, dünya üzerindeki bilinen en büyük Müslüman Mezarlığı olması ve taşıdığı tarihsel önem nedeniyle UNESCO'nun Dünya Kültür Mirası Geçici Listesi'nde yer almaktadır. Mezar taşı olarak, bölgede oldukça yaygın olarak bulunan ve piroklastik bir kaya türü olan ignimbiritler kullanılmış olup, yumuşak olmaları ve kolay işlenebilmelerini nedeni ile üzerlerine çeşitli motifler ve yazıtlar işlenmiştir. Ancak söz konusu mezar taşları, yaklaşık 800 yıllık süreç içerisinde bozunma etkilerine maruz kalmıştır. Mezar taşları incelendiğinde dikkati çeken en önemli unsur, birçok mezar taşının orta bölgelerine yakın kısımlarından kırılmış olmasıdır. Bu çalışma kapsamında Ahlat Selçuklu mezar taşlarının bozunmasına neden olan unsurların açığa çıkarılması amacıyla taze ignimbirit örnekleri üzerinde deneysel çalışmalar yapılmış ve özellikle kılcal su emmenin bozunma üzerindeki etkisi araştırılmıştır. Buna göre, ignimbiritlerin yüksek gözenekliliği ve kılcal su emme özelliği mezar taşlarının bozunmasındaki en önemli etkendir
Impact of Jet-Grouting Pressure on the Strength and Deformation Characteristics of Sandy and Clayey Soils in the Compression Zone
(Korean Society of Civil Engineers-ksce, 2019) Akin, Mutluhan; Akkaya, Ismail; Akin, Muge K.; Ozvan, Ali; Ak, Yusuf
Jet-grouting as a soil improvement method is extensively preferred in today's civil engineering practice. High-modulus grout columns constructed by extremely high jetting pressures displace the surrounding soil causing a densification in soil particles. Accordingly, the strength as well as the deformation characteristics of subsurface soils are relatively improved across the compression zone which is under the influence of high jetting pressure. In this study, the modification of soil properties in compression zone after jet-grouting in sandy and clayey soils is investigated by standard penetration tests (SPT) and multi-channel analysis of surface waves (MASW) performed at a couple of construction sites along established jet-grout column rows. The in-situ test results point out significant improvement of the measured parameters compared to initial values. The rate of enhancement in the compression zone is higher in sandy strata than that of clayey deposits. The strengthening of soil due to jetting pressure is validated by finite element analyses as well. Furthermore, very low shear strain values are obtained in clayey soils with respect to the improved characteristics of compression zone representing extremely low shear deformation under foundation.
Investigation of the Effect of Surface Coating Resin Application on Salt Crystallization Resistance in Ignimbrites With Different Welding Degrees
(Springer Heidelberg, 2025) Varol, Oguen Ozan; Akin, Mutluhan; Dincer, Ismail
In this study, the salt crystallization resistance of ignimbrites obtained from Nev & scedil;ehir and Kayseri regions in untreated and water-repellent-treated conditions was determined. X-Ray Fluorescence Spectroscopy (XRF) and X-Ray Diffraction (XRD) analyses were conducted to determine the mineralogical-petrographic characteristics of the ignimbrites, Scanning Electron Microscopy (SEM) analyses were performed to identify changes in the internal structure of the samples before and after salt crystallization, and Brunauer-Emmett-Teller (BET) analyses were carried out to determine changes in pore structures. In the conducted study, both untreated and treated samples were tested for their physical and mechanical properties, including unit weight, uniaxial compressive strength, ultrasonic wave velocity, water adsorption by weight, porosity, Shore Leeb hardness, and point load strength. It was found that the welding degree of the ignimbrites had a significant impact on the effectiveness of the water repellent application. The most important conclusion drawn from this study is that determining the welding degrees of ignimbrites before surface protective coating processes is crucial because the welding degree directly affects the porosity, strength, and durability of the stone. Especially for ignimbrite samples used in historical and hospitality structures in regions such as Nev & scedil;ehir and, Kayseri understanding these properties helps to select the appropriate surface coating, enhancing the material resistance against decay processes.
Kayma Dalgası Hızı (Vs) Kullanılarak Erciş (Van) Yerleşim Alanının Sıvılaşma Potansiyelinin Değerlendirilmesi
(2017) Akin, Mutluhan; Özvan, Ali; Akkaya, İsmail; Övün, Uğur; Akin, Muge
Van İli, Erciş İlçesi yerleşim alanı ve çevresi Kuvaterner yaşlı güncel çökeller üzerinde yeralan, yeraltısuyu seviyesi sığ, çevresinde tarihsel ve aletsel dönemde büyük deprem üretmiş aktif fayların yeraldığı, 23 Ekim 2011 Van (Mw=7,1) depremi sonrasında belli kesimlerinde sıvılaşma olayının gerçekleştiği önemli bir yerleşim yeridir. Tüm bu veriler, Erciş ve yakın çevresi için olası büyük bir depremde sıvılaşma ve yanal yayılma türü yüzey deformasyonlarının meydana gelebileceğini işaret etmektedir. Bu nedenle çalışmada, Kayma dalga hızları (Vs) kullanılarak Erciş yerleşim alanı ve çevresinin üç farklı deprem senaryosu için sıvılaşma analizleri yapılmıştır. Yapılan değerlendirmeler sonucunda, Erciş merkezinin yoğun olarak üzerinde bulunduğu eski göl çökellerinin sıvılaşma potansiyelinin \"düşük-orta\" olduğu belirlenmiştir. İnceleme alanının Van Gölü\"ne yakın kıyı kesimleri ile inceleme alanının batısında sıvılaşma potansiyelinin diğer kesimlere göre daha yüksek olduğu hesaplanmıştır. Ayrıca, Erciş yerleşim alanında 23 Ekim 2011 Van depremi sonrasında arazide gözlenen yanal yayılmalar ve sıvılaşmaların bu çalışmada ön görülen senaryolardaki sınırlarla örtüştüğü belirlenmiştir
A New Quantitative Welding Degree Classification for Ignimbrites
(Springer, 2023) Akin, Mutluhan; Topal, Tamer; Dincer, Ismail; Akin, Muge K.; Ozvan, Ali; Orhan, Ahmet; Orhan, Ayse
As a pyroclastic rock type, ignimbrites may reveal varying degrees of welding depending on the temperature (> 535 celcius) and overburden pressure conditions during its formation. The welding degree of ignimbrites increases as the formation temperature and the thickness of the overburden deposit in the depositional environment escalate, which are the most crucial factors controlling the rate of welding in ignimbrites. With the increasing temperature, plastic deformation is observed in ignimbrites and the glassy minerals are being welded. Furthermore, the thickness of the overburden causes the deformation of the ash matrix in ignimbrites at the lower sections and the pumice grains are flattened at different rates. An increase in the degree of welding of ignimbrites causes an improvement in the physical and mechanical properties of the rock material as well. Within the scope of this research, petrographical, mineralogical, and geochemical studies were carried out on a total of 16 different ignimbrite types, which have different color and texture properties, obtained from three different regions of Turkey (Kayseri, Nevsehir, Ahlat) where ignimbrites extensively crop out, and the physical and mechanical properties of these samples were revealed. Consequently, a new welding classification was developed for ignimbrites considering the uniaxial compressive strength and dry unit weight. The proposed welding classification consists of six classes ranging from non-welded to highly welded. When the welding degrees of the selected ignimbrites are evaluated, Kayseri ignimbrites mostly exhibit moderate welding characteristics. Nevsehir ignimbrites, on the other hand, have a low welding degree whereas the degree of welding in Ahlat ignimbrites may vary from low to high. Additionally, long and short axis lengths of pumice grains in the ignimbrite specimens were determined by measuring under the microscope, and shape ratios were determined by different shape parameter evaluation methods. As a result, it has been concluded that the pumice grains in Kayseri and Ahlat ignimbrites have a more lenticular structure than the pumice grains in Nevsehir ignimbrites. Eventually, the welding degree classes of ignimbrites and the classification developed by using threshold values of the oblateness ratio (OR) values of pumice grains at different welding degrees are quite compatible. The proposed welding degree classification is of great importance in the selection of ignimbrites widely used as dimension stone and in terms of engineering classification of this rock type as well as it will guide to the scientific studies to be performed on ignimbrites with varying physical and mechanical properties.
Slope Stability Problems and Back Analysis in Heavily Jointed Rock Mass: a Case Study From Manisa, Turkey
(Springer Wien, 2013) Akin, Mutluhan
This paper presents a case study regarding slope stability problems and the remedial slope stabilization work executed during the construction of two reinforced concrete water storage tanks on a steep hill in Manisa, Turkey. Water storage tanks of different capacities were planned to be constructed, one under the other, on closely jointed and deformed shale and sandstone units. The tank on the upper elevation was constructed first and an approximately 20-m cut slope with two benches was excavated in front of this upper tank before the construction of the lower tank. The cut slope failed after a week and the failure threatened the stability of the upper water tank. In addition to re-sloping, a 15.6-m deep contiguous retaining pile wall without anchoring was built to support both the cut slope and the upper tank. Despite the construction of a retaining pile wall, a maximum of 10 mm of displacement was observed by inclinometer measurements due to the re-failure of the slope on the existing slip surface. Permanent stability was achieved after the placement of a granular fill buttress on the slope. Back analysis based on the non-linear (Hoek-Brown) failure criterion indicated that the geological strength index (GSI) value of the slope-forming material is around 21 and is compatible with the in situ-determined GSI value (24). The calculated normal-shear stress plots are also consistent with the Hoek-Brown failure envelope of the rock mass, indicating that the location of the sliding surface, GSI value estimated by back analysis, and the rock mass parameters are well defined. The long-term stability analysis illustrates a safe slope design after the placement of a permanent toe buttress.
A Study of the Relationship Between the Pressuremeter Modulus and the Preconsolidation Pressure Around a Thrust Fault
(Springer, 2019) Ozvan, Ali; Ozvan, Elif E.; Akkaya, Ismail; Akin, Mutluhan; Akin, Muge K.
The study area is in a zone under the influence of the Lake Van water changes and the Van fault, which caused a destructive earthquake in 2011. Due to the level changes of Lake Van, sediments with different thicknesses as well as grain sizes were deposited in this region and the characteristics of these sediments were significantly affected by the morphology and lake water fluctuations in the past. A total of six boreholes were drilled along a 3-km line within the study area to determine the preconsolidation pressure (sigma(pc)) and the pressuremeter test values of the clayey levels of old lake deposits-which are known to have different physical and mechanical properties-with hopes to gain an insight on how they influence the mechanical tests performed in the field and in laboratory conditions. The relationship between these values was also statistically evaluated. When both datasets were evaluated together, it was determined that the stresses in the area close to the Van Thrust Fault plane caused deformations in the soil, which in turn affected the hanging-wall block of the thrust fault in particular. The inspection of E-M and sigma(pc) values for the area within the primary compression zone of the Van Fault revealed that both values of the boreholes on the footwall block were higher compared to other boreholes close to the lake (southwest). This finding indicates that the fault stresses at the footwall block of the fault plane enhance the mechanical characteristics of the soil. The data obtained were also evaluated using regression analysis. Relationships between all available data were investigated and a high coefficient of determination was derived between the Menard deformation modulus (E-M) and the preconsolidation (sigma(pc)) pressure.