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Öğe Behavior of a dense nonplastic silt under cyclic loading(2018) Tanrınıan, Nazar; Karakan, Eyyub; Sezer, Alper; Altun, Selim…Öğe Cyclic undrained behavior and post liquefaction settlement of a nonplastic silt(Elsevier Sci Ltd, 2019) Karakan, Eyyub; Tanrinian, Nazar; Sezer, AlperThis study presents an investigation into liquefaction and post-liquefaction behavior of a nonplastic silt under cyclic loading. A systematic approach was adopted for assessment of above-mentioned behavior by performing cyclic triaxial tests on saturated specimens in terms of pore water pressure build-up characteristics, effective stress, number of cycles and double amplitude axial strain. The specimens, consolidated under an effective confining pressure of 100 kPa, were prepared at relative densities ranging among 30-80%. The results revealed that the axial strains of specimens of lower relative densities were increased at higher CSR levels. For prediction of pre- and post-liquefaction behavior, a family of curves for establishing relationships among factor of safety to liquefaction, post-liquefaction volumetric strain and relative density were established. These curves, along with the calculation of post-liquefaction volumetric strain, may be useful in estimation of settlements of silt after being subjected to cyclic loading.Öğe Determination of the Cyclic Properties of Silty Sands(Igi Global, 2018) Karakan, Eyyub; Altun, SelimLiquefaction may be triggered by cyclic loading on saturated silty sands, which is responsible of severe geotechnical problems. Development of excess pore water pressure in soil results in a liquid-like behavior and may be the reason of unavoidable superstructural damage. In this study, in order to investigate the behavior of saturated silty sands exposed to cyclic loading under undrained conditions, a systematic testing program of stress-controlled cyclic triaxial tests was performed on specimens of different silt contents, under different loading conditions and environment. The effect of parameters such as silt content on the liquefaction behavior of specimens was studied. Pore water pressure and shear strain curves were obtained for the silty sands. Furthermore, the boundaries existing in the literature on sands are compared with the results current research, on silty sands. Conclusively, the outcomes of this study were useful to develop insight into the behavior of clean and silty sands under seismic loading conditions.Öğe Effect of clay fraction and mineralogy on fall cone results of clay-sand mixtures(Elsevier, 2020) Karakan, Eyyub; Shimobe, Satoru; Sezer, AlperIn this study, the relationships among plasticity ratio, clay fraction and liquidity index of clay-sand mixtures were investigated. Two types of clays, namely, kaolin (K) and calcium-montmorillonite (CM) were used to prepare clay-sand mixtures of different grain size distributions. Clays were mixed with clean sands of two different grain size distributions (well graded sand-SW and poorly graded sand-SP) at clay contents ranging between 0% to 100% by increments of 10%, in terms of dry weight. Fall cone, Casagrande, plastic limit and laboratory vane shear tests were performed on various clay- sand mixtures with different clay contents. Experimental results revealed that, above 100% water content, undrained shear strength values of CMSW and CMSP mixtures were determined to be around 50 kPa. on the other hand, undrained shear strengths of KSW and KSP mixtures are around 30 kPa, for a water content of 30%. Average undrained shear strengths of CMS and KS mixtures at their plastic limits are obtained as 210.68 kPa and 119.62 kPa, respectively. Average undrained shear strengths of these mixtures at their liquid limits are determined to be 2.40 kPa and 1.88 kPa, respectively. It is concluded that various mechanisms control liquid and plastic limits of clay-sand mixtures which are influenced by gradation of sand, clay content as well as origin of clay. As a result, several relationships among parameters including water content, liquidity index, undrained shear strength, cone penetration depth, fall cone liquid limit and Casagrande liquid limit were presented.Öğe Effects of Fibre Reinforcement on Liquefaction Behaviour of Poorly Graded Sands(Elsevier Science Bv, 2016) Eskisar, Tugba; Karakan, Eyyub; Altun, Selim; Drusa, M; Yilmaz, I; Marschalko, M; Coisson, E; Segalini, AThe objective of this study is to evaluate the liquefaction behaviour of fibre reinforced sand concerning the lower and upper limits of medium relative densities of 50% and 70%, respectively. A systematic testing program of the stress-controlled cyclic triaxial tests was performed on saturated sand samples with and without fibre reinforcements under undrained conditions. The confining pressure for all test cases was 100 kPa reflecting the actual overburden pressure in field conditions. The effect of parameters such as fibre content (0.25%, 0.50%, and 1%) and fibre length (6 mm and 12 mm) on the liquefaction behaviour of unreinforced and reinforced specimens was studied. Upon increasing the fibre content and fibre length, the number of loading cycles leading to liquefaction increased. Pore water pressure and shear strain curves are obtained for the fibre reinforced medium dense sands. Furthermore, the boundaries presented in the literature on the sands are shown in comparison with the results of fibre reinforced sands of this study. As a conclusion, the outcomes of this study are useful to develop insight into the behaviour of clean and fibre reinforced medium dense sands under seismic loading conditions. Based on the test results, it was found that the number of loading cycles has significant influence on the generation of excess pore pressure. (C) 2016 The Authors. Published by Elsevier Ltd.Öğe Evaluating the Mechanical Behaviour of Geotextile Reinforced Sand(Turkish Chamber Civil Engineers, 2015) Tuna, Sahin Caglar; Karakan, Eyyub; Altun, SelimIt is important to determine the mechanical properties of reinforced soils, since they are extensively used in practice. In this study, laboratory triaxial tests and direct shear tests were carried out in order to determine the stress-strain and dilation characteristics of geotextile-reinforced river sand. The mechanical behaviour of the composite material was investigated through varying the type of geotextile and confining pressure. Interface properties of geotextile-reinforced samples were evaluated with the direct shear tests. The results demonstrated that geotextile inclusion increases the peak strength, and reduces dilation especially at higher confining pressures.Öğe Evaluation of Cyclic Stress-Strain and Liquefaction Behavior of Izmir Sand(Springer Heidelberg, 2014) Eskisar, Tugba; Karakan, Eyyub; Altun, SelimThis paper presents the results of a series of cyclic triaxial tests carried out on sands with different index properties. Samples from three grain-size distributions of Izmir (Turkey) sand were tested under consolidated-undrained conditions. The tests were performed under two different effective confining pressure values (100 and 200 kPa). The relative densities of the specimens were 30 and 50%. The results showed that the relative density plays a dominant role in the liquefaction behavior of the sand, whereas the confining pressure increase has greater effects on the stress-strain properties of the sand. It was observed that the relationship between the grain-size diameters and cyclic stress ratios of the sands would be more realistic. It was found that the pore water pressure generation curve falls outside the narrow band proposed by previous studies and a greater coefficient is required for the cycle ratio depending on the soil properties and test conditions. The shear moduli of the sands increased independently of the mean diameter with the relative density under a confining pressure of 100 kPa. Under a confining pressure of 200 kPa, the shear moduli increased with the uniformity coefficient of the sand. Increments in the relative density resulted in a slight increment of the shear moduli for the sands. The goal of the current study was to provide an understanding of the liquefaction and stress-strain behavior of Izmir sand, which represents the material of similar sites with loose alluvial sediments located in earthquake-prone areas found around the world.Öğe Evaluation of dependency of compression index on toughness limit for fine-grained soils(Springer London Ltd, 2023) Shimobe, Satoru; Karakan, Eyyub; Sezer, AlperPrediction of the ultimate settlement is vital for the assessment of the service life of a structure, particularly when it is underlain by fine-grained soils. As known, this value is a function of the compression index (C-c) of soils, which can simply be found by performance of oedometer tests. For this purpose, more than 2000 test results from past studies were compiled to constitute a database. Then, multiple linear regression analyses were employed to predict the C-c parameter by use of toughness limit (TL) and a function of this parameter, namely the soil state index (SSI). It was noticed that SSI was a better predictor of C-c, in comparison with TL. Prediction ability of many equations from literature was questioned, and it was concluded that these equations were good predictors of their own data. Moving to a generalized behavior, data show a more scattered structure, which needs more sophisticated methods using above-mentioned parameters as inputs. In this regard, artificial neural networks were employed to estimate the C-c by use of single input parameters: TL or SSI. Additionally, a combination of Atterberg limits was also instructed as inputs for prediction of C-c. A comparative analysis of the effects of learning algorithm, input data, and number of neurons in hidden layer was given. It was concluded that the TL and SSI are reasonable predictors of compression index.Öğe Evaluation of dependency of compression index on toughness limit for fine-grained soils [2](Springer London Ltd, 2023) Shimobe, Satoru; Karakan, Eyyub; Sezer, AlperPrediction of the ultimate settlement is vital for the assessment of the service life of a structure, particularly when it is underlain by fine-grained soils. As known, this value is a function of the compression index (C-c) of soils, which can simply be found by performance of oedometer tests. For this purpose, more than 2000 test results from past studies were compiled to constitute a database. Then, multiple linear regression analyses were employed to predict the C-c parameter by use of toughness limit (TL) and a function of this parameter, namely the soil state index (SSI). It was noticed that SSI was a better predictor of C-c, in comparison with TL. Prediction ability of many equations from literature was questioned, and it was concluded that these equations were good predictors of their own data. Moving to a generalized behavior, data show a more scattered structure, which needs more sophisticated methods using above-mentioned parameters as inputs. In this regard, artificial neural networks were employed to estimate the C-c by use of single input parameters: TL or SSI. Additionally, a combination of Atterberg limits was also instructed as inputs for prediction of C-c. A comparative analysis of the effects of learning algorithm, input data, and number of neurons in hidden layer was given. It was concluded that the TL and SSI are reasonable predictors of compression index.Öğe Evaluation of effect of limited pore water pressure development on cyclic behavior of a nonplastic silt(Japanese Geotechnical Soc, 2019) Karakan, Eyyub; Sezer, Alper; Tanrinian, NazarIn this study, an experimental procedure was adopted to evaluate cyclic behavior of silts of pore water pressure ratios less than 50%. A commercially available nonplastic silt was used to eliminate the effects of plasticity. All the specimens were isotropically consolidated under 100 kPa and later subjected to cyclic triaxial compression tests. in this regard, dependence of cyclic stress ratio (CSR), initial relative density (D-r) and cyclic axial strain (epsilon(sa)) on pore water pressure generation pattern - either at small or large deformation levels - were evaluated. It was inferred that, volume changes in silt due to the reconsolidation after cyclic loading with an induced pore water pressure ratio (R-u) less than 50% shows limited liquefaction. (C) 2019 Production and hosting by Elsevier B.V. on behalf of the Japanese Geotechnical Society.Öğe Evaluation of Excess Pore Water Pressure Behaviour During Cyclic Triaxial Tests on a Non-plastic Silt(2018) Tanrınıan, Nazar; Karakan, Eyyub; Sezer, Alper…Öğe Improved dataset for establishing novel relationships between compaction characteristics and physical properties of soils(Springer Heidelberg, 2021) Shimobe, Satoru; Karakan, Eyyub; Sezer, AlperIn the past, several studies were performed for assessment of compaction properties of different types of soils. A comprehensive evaluation of compaction parameters is essential for engineers working in practice. The main goals of compaction in landfills including highways and railways can be listed as reducing permeability and developing strength as well as enhancing the stability of soils. Literature includes various correlations proposed for establishing the link between the compaction properties of soils and Atterberg limits. Besides, many researchers performed laboratory studies to obtain correlations among soil index, strength, compression, and compaction characteristics of soils. In this study, in addition to authors' own data composed of compaction, strength, index, and consistency identifiers of sand-clay mixtures from three different types of sands (S1, S2, Q) and two types of clays (kaolinite and bentonite), a vast amount of data from past studies including tests on different types of soils around the world were also compiled. The global database was evaluated to propose novel correlative relationships among compaction characteristics, grain size distribution properties, and Atterberg limits. Proposed equations and relationships for estimation of compaction characteristics seem to be viable to use in practice.Öğe Insights on the role of local site effects on damage distribution in the Izmir metropolitan area induced by the October 30, 2020 Samos earthquake(Japanese Geotechnical Soc, 2023) Chiaradonna, Anna; Karakan, Eyyub; Kincal, Cem; Lanzo, Giuseppe; Monaco, Paola; Sezer, Alper; Karray, MouradOn the 30th of October 2020, a 6.6 magnitude earthquake occurred 14 km north of Samos Island, causing 119 casualties (117 in Izmir, Tu & BULL;rkiye, and 2 in Samos, Greece) and significant damage in the 3rd biggest city of Tu & BULL;rkiye, Izmir. Although the city is roughly 70 km far away from the epicenter, the damage was significant and concentrated in the city center settled on alluviums. This paper aims to analyze the distribution of damage in Izmir province, by crosschecking the recorded motions, the subsoil conditions and the evidence of damage as collected by an ad-hoc on-site reconnaissance. The intrinsic behavior of the Samos earthquake was investigated by employing three different ground-motion prediction equations. The results of the analyses revealed that site effects play a significant role in the amplifi-cation of ground motions, and valley effects are responsible for the concentration of damage. The damage in buildings was classified in terms of the intensity and structural typologies for the 30 districts of Izmir metropolitan area. In-depth analysis of the distribution of damages revealed that the earthquake caused damage all over the boundaries of Izmir province, and the concentration of damage in Bornova and Kars & DBLBOND;iyaka districts has a clear correlation with double resonance effects.& COPY; 2023 Production and hosting by Elsevier B.V. on behalf of The Japanese Geotechnical Society. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).Öğe The Liquefaction Behavior of Poorly Graded Sands Reinforced with Fibers(Hindawi Ltd, 2018) Karakan, Eyyub; Eskisar, Tugba; Altun, SelimThis study focuses on the performance of fibers, improving the resistance to liquefaction in loose sands, medium sands, and dense sands in Izmir, Turkey. A systematic testing schedule consisting of cyclic triaxial tests was held under stress-controlled and undrained conditions on saturated sand specimens with and without fiber reinforcements. The major parameters having effects on the dynamic behavior such as fiber content, fiber length, and relative density on the liquefaction behavior and the excess pore water pressure developments of specimens with and without fibers were investigated. If the fiber content or the fiber length was increased in the specimens, higher number of loading cycles was needed in order to experience the liquefaction of sands. The reinforcement effect in medium-dense specimens was found to be apparently distinctive compared to loose specimens. The curves of pore water pressures and shear strains were achieved for the fiber-reinforced sands. The boundaries of pore water pressure curves presented in the literature on the clean sands were utilized in comparison with the pore water pressure curves of fiber-reinforced sands of this study. As a conclusion, the results presented in this study are useful to develop insight into the behavior of clean and fiber-reinforced sands under seismic loading conditions. Based on the test results, it was found that the number of loading cycles had a strong impact on the excess pore pressure generation.Öğe Liquefaction Behavior of Silt Sand Mixtures and Post Liquefaction Volumetric Strain Properties(Turkish Chamber Civil Engineers, 2016) Karakan, Eyyub; Altun, SelimIn this study, the liquefaction behavior silty sand mixtures and volumetric deformation properties were investigated. The study was implemented on samples of silt sand mixtures obtained during an excavation at Bayrakh, Izmir, Turkey. In order to investigate the liquefaction behavior of silty sand, undrained cyclic triaxial compression tests were carried out according to JGS 0542-2000, for 8 different fines contents (0, 5, 10, 20, 40, 60, 80, 100%). To determine the volumetric deformation properties, the water content change was measured by allowing drainage into a burette upon completion of a cyclic test. The liquefaction criteria was determined by using intergranular-interfme void ratios. A threshold fines content to serve as liquefaction criterion has also been determined. The volumetric deformation properties behavior were reviewed depending on the silt content.Öğe Nonlinear regression methods and genetic algorithms for estimation of compression index of clays using toughness limit(Techno-Press, 2024) Shimobe, Satoru; Karakan, Eyyub; Sezer, AlperMeasurement or prediction of compression index ( C c ) of soils is essential for assessment of total and differential settlement of structures. It is a well-known fact that this parameter is controlled by several index identifiers of soil including initial void ratio, Atterberg limits, overconsolidation ratio, specific gravity, etc. Many studies in the past proposed relationships for prediction of C c based on different index properties. Therefore, this study aims to present a comparison of previously proposed equations for estimation of C c . Data from literature was compiled, and a total of 90 and 623 test results on remolded and undisturbed specimens were used to question the validity of previously proposed equations. Nevertheless, the modeling ability of 7 and 12 equations for estimation of C c of remolded and undisturbed soils were questioned by use of compiled data. Moreover, new empirical relationships based on initial void ratio and toughness limit for prediction of C c was proposed by use of nonlinear multivariable regression and evolutionary based regression analyses. The results are promising -the performances of models established are quite acceptable, which are verified by statistical analyses.Öğe Türkiye Mw 7.7 Pazarcık and Mw 7.6 Elbistan earthquakes of February 6th, 2023: Contribution of valley effects on damage pattern(Elsevier Sci Ltd, 2024) Karray, Mourad; Karakan, Eyyub; Kincal, Cem; Chiaradonna, Anna; Gul, Tolga Oktay; Lanzo, Giuseppe; Monaco, PaolaOn February 6th, 2023, southeastern T & uuml;rkiye was shaken by two catastrophic earthquakes, close to northwestern Syrian border. The first earthquake (Pazarc & imath;k) occurred 45 km west of Gaziantep at 1:17:32 (UTC), with a shallow strike-slip faulting at a depth of approximately 8.6 km and a moment magnitude (MW) of around 7.7. The second event (Elbistan) took place 9 h later, 66 km north-east of Kahramanmaras, city center, also with shallow strike-slip faulting at a depth approximately 7 km and an MW of around 7.6. Turkish authorities reported a death toll of over 59,000 in T & uuml;rkiye and about 8500 in Syria. The destructive effect of the earthquake resulted from widespread strong ground shaking, a rupture length exceeding 300 km, causing collapse of a large number of buildings. The catastrophic destruction of the built environment was accompanied by a range of other earthquake-related effects, including fault ruptures, landslides, and soil liquefaction. The aim of the study is to analyze the distribution of ground motion and their relationships with the observed damages for the two events. Spectral accelerations of key importance were assessed across a large area in the southeastern part of T & uuml;rkiye. Notably, these accelerations were generally much higher than existing design spectra. A significant correlation between the observed concentration of damage and the significant amplification of motion induced by local soil conditions (such as soft soils and valley effects). The distinct tectonic structure of the region could be the main reason for the high amplification in the valleys (associated with basin effects), even at large distances from the epicenter, especially in correspondence with the bidimensional grabentype geological structures. The investigation delved into the analysis of four specific regions in detail: Antakya and Hassa (both in the Hatay province), Kahramanmaras, and Goksun. Notably, the observable valley effects were found to play a significant role and could account for the significant damage observed in these regions.
