Browsing by Author "Dincer, Ismail"

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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.
The Effects of Discontinuity Surface Roughness on the Shear Strength of Weathered Granite Joints
(Springer Heidelberg, 2014) Ozvan, Ali; Dincer, Ismail; Acar, Altay; Ozvan, Burcu
Surface roughness is one of the most important parameters governing the shear strength of rock discontinuities. Roughness types may vary based on genesis, physico-mechanical, and mineralogical properties of rocks. In this study, granite samples representing three different weathering degrees were selected to evaluate the effects of surface roughness and weathering degree on shear strength. To this aim, we determined the profile roughness coefficient (PRC), profile roughness angle (PRA), and joint roughness coefficient (JRC) for the selected fresh and weathered granite joint samples. Values of PRC were in the range of about 1.043-1.073, and PRA and JRC varied in the ranges of 16.67-21.45 and 12-18, respectively. Weathering led to the increment of joint surface roughness of the selected granitic joints due to the higher resistance of quartz crystals in the weathered matrix. However, the increment in surface roughness did not result in an increase in the shear strength. On the contrary, the shear strength of discontinuities dramatically decreased.
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.
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.
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.
Quality Assessment of Geo-Materials for Coastal Structures (Yumurtalik, Turkey)
(Taylor & Francis inc, 2011) Ozvan, Ali; Dincer, Ismail; Acar, Altay
Rubble mound breakwater is one of the most important coastal engineering structures for shore and harbor protection. Standard rock quality evaluation processes were performed on massive basalt, vesicular basalt, crystallized limestone, and micritic limestone from southeast of Turkey. The rock types were evaluated within five different rock quality classification systems (CIRIA, CUR, CETMEF 2007; Lienhart 1998; Winkler 1986; Fookes et al. 1988; BS 812). The methods of CIRIA, CUR, CETMEF (2007) and Lienhart (1998) were shown to be more successful than other methods, which are insufficient to explain rock quality. Massive basalt and micritic limestone can be used as armourstone, filter layer, and core materials, but vesicular and crystallized limestone provided engineering requirements for only core materials. Vesicular basalt and crystalline limestone exhibited few poor features in terms of strength, such as iddingsite, stylolites, and micro cracks. These features can favorably affect rock strength, and oppositely affect rock quality.