WoS İndeksli Yayınlar Koleksiyonu
Permanent URI for this collectionhttps://hdl.handle.net/20.500.12573/394
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Article Citation - WoS: 18Rockfall Hazard Assessment Around Ankara Citadel (Turkey) Using Rockfall Analyses and Hazard Rating System(Springer, 2020-03-09) San, Nyein Ei; Topal, Tamer; Akin, Muge K.Ankara Citadel which is one of the important cultural heritages in Turkey settles in the oldest part of Ankara. Rockfall event has occurred around the Citadel located on a steep hill where andesite is exposed. The rockfall problem causes a great risk to the surrounding area where road, school, floral shops, car parking. Therefore, the major aim of this research is to reveal the rockfall risk around the castle. The rockfall problems around the Ankara Citadel may be linked with weathering, freezing-thawing, earthquake, and cooling joints, and effects or combination of these in the rock units. The rockfall-related hazard at the Citadel is assessed by 2-D rockfall analyses along several profiles in this investigation. Field observations and stability analyses (kinematic and limit equilibrium) of the slopes reveal that there exist many blocks ready to fall down. Four different andesite block sizes measured in the field are separately analyzed on the basis of bounce height, fall-out distance, velocity and kinetic energy of the blocks. The obtained data are evaluated to define the possible rockfall-based hazard zones. Based on the danger zones acquired from the rockfall analyses, the removal of the fallen and loosen andesite blocks and the installation of catch barriers with suggested properties are recommended. Besides, the risk integrated into rockfall hazard rating system on the basis of structural and morphological criteria of the rock mass reveals that medium risk category to be mitigated by light remedial measures for the indicative protection exists in the study area.Article Citation - WoS: 15Citation - Scopus: 18Evaluation of Seismic Site Classification for Kahramanmaras City, Turkey(Springer, 2021-01-28) Naji, Dalia Munaff; Akin, Muge K.; Cabalar, Ali FiratThis paper presents a study on the seismic site classification map using the geophysical tests in Kahramanmaras city located at a place where African, Anatolian, and Arabian plates meeting in southern-central Turkey. Generating seismic site classification maps in accordance with National Earthquake Hazards Reduction Program (NEHRP) has become a more significant criterion for earthquake hazard estimations. The SPT-N values obtained from the field studies at 287 boreholes within the upper 30 m were used to describe the subsurface conditions in the region. The shear wave velocity (V-S) values in the study area were obtained by implementing Multichannel Analysis of Surface Waves (MASW) and Microtremor Array Method (MAM) measurements tests. An approach proposed by Boore (Boore, Bull Seismol Soc Am 94:591-597, 2004) for the cases where the V-S measurements do not reach 30 m depth has also been adopted by correlating the shallow shear wave velocity with V-S30. The resulting site classification maps estimate that the study area is predominantly classified as soil site class C, while the small areas were rarely classified as soil site class D and B. Furthermore, a systematic analysis based on a comparative study of the present research and the published correlations for seismic site classification with V-S30 values has been carried out using Geographical Information System (GIS). Evidently, the V-S30 based seismic site classification maps could be effectively used by researchers and engineers for the purpose of land-use planning and urban development in earthquake-prone regions.Article Citation - WoS: 14Citation - Scopus: 16Dynamic Soil Characterization and Site Response Estimation for Erbaa, Tokat (Turkey)(Springer, 2016-03-11) Akin, Muge K.; Kramer, Steven L.; Topal, TamerSite amplification is one of the most important factors controlling damage in urban areas through strong earthquakes. Local site effects play an important role in earthquake-resistant design and should be considered for site response analyses. In this study, ground response analyses in Erbaa, Turkey, a settlement in the North Anatolian Fault Zone, using one-dimensional equivalent linear analysis and empirical approaches based on shear wave velocity profiles are evaluated and compared. The ground response analyses were performed with consideration of shear wave velocity, and modulus reduction and damping behavior for different confining pressure and plasticity index-dependent models. The results of ground response analyses and amplification values from empirical equations using shear wave velocity are illustrated in terms of amplification and predominant period maps of the seismically active Erbaa settlement area. The comparison has been made in these produced maps of the study area in order to evaluate different site response analyses.Article Citation - WoS: 2Citation - Scopus: 4A Study of the Relationship Between the Pressuremeter Modulus and the Preconsolidation Pressure Around a Thrust Fault(Springer, 2019-10) 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.Article Citation - WoS: 8Citation - Scopus: 9A New Quantitative Welding Degree Classification for Ignimbrites(Springer, 2023-06-28) Akin, Mutluhan; Topal, Tamer; Dincer, Ismail; Akin, Muge K.; Ozvan, Ali; Orhan, Ahmet; Orhan, AyseAs 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.