Yazar "Karademir, Tanay" seçeneğine göre listele
Listeleniyor 1 - 9 / 9
Sayfa Başına Sonuç
Sıralama seçenekleri
Öğe 2D Surface Topography Alterations of Different Geomembrane Liners: Grain Shape, Relative Density and Loading Perspectives(Osmaniye Korkut Ata Üniversitesi, 2024) Karademir, TanaySurface topography is of importance in playing a major role for the mobilized mechanical behavior, and hence, the strength-stability performance of composite layered systems containing synthetic geomembrane liner and natural granular sand. The 2D surface topography alterations of different geomembranes were experimentally be studied by performing profile relief measurements for detecting and determining 2D surface topographical characteristics of different geomembrane liner sheets produced from distinctive polymeric resins (HDPE, LLDPE, PVC) previously subjected to abrasive action of granular sand grains at different relative densities (Dr) and dissimilar particle shape (rounded or angular), and additionally at various loading conditions. The surface topographical characteristics as evident on the detected profiles including asperity features such as size, shape, and spacing of material dislocations comprised of peaks and valleys in the topographies were different and unique to geomembrane type. As such, the softer and the more flexible the geomembrane liner sheet in an order of HDPE, LLDPE, PVC becomes, the greater the abrasion has developed in that the surface topography demonstrated more severe peaks and valleys. Further, the angular features of sand grains led to the mobilization of more violent abrasive action in that angular particles were able to penetrate into the surface of geomembrane liner, and thus, gouge on a trajectory along the surface. The dimensions and spacing of peaks and valleys for the surface topography were small-scale in relatively stiffer geomembrane liner sheet of HDPE in which the surface topography did not possess sharp corners such that the transitions from peaks to valleys to peaks were smooth and rounded as compared to that of LLDPE as well as PVC geomembranes where sharp and rough transitions from peaks to valleys to peaks exhibited. The quantification of surface topography alterations of different geomembranes by means of the computed values of average roughness (Ra) determined for the measured surface topographies of the liners unveiled that the Ra (i.e. surficial topographical changes) increases with an increase in load, relative density, particle angularity of grain shape, and softness of geomembrane liner sheet.|Yüzey topografyası, mobilize edilmiş mekanik davranışta ve dolayısıyla sentetik geomembran astar ve doğal granüler kum içeren kompozit katmanlı sistemlerin mukavemet-stabilite performansında kritik bir rol oynamada önemlidir. Farklı geomembranların, 2 boyutlu yüzey topografisi değişiklikleri, daha önce farklı bağıl yoğunluklarda (Dr) ve farklı danecik şekillerinde (yuvarlak veya köşeli) ve ayrıca çeşitli yükleme koşullarında granüler kumun aşındırıcı etkisine maruz bırakılmış değişik polimerik reçinelerden (HDPE, LLDPE, PVC) üretilen farklı geomembran astar tabakalarının 2 boyutlu yüzey topografyası karakteristik özelliklerini tespit etmek ve belirlemek için profil kabarma ölçümleri gerçekleştirilerek deneysel olarak incelenmiştir. Topografyalardaki tepe ve vadilerden oluşan malzeme dislokasyonlarının boyutu, şekli ve aralıkları gibi pürüzlülük özellikleri de dahil olmak üzere tespit edilen profillerde açıkça görülen yüzey topoğrafik özellikleri farklı ve geomembran tipine özgüdür. Bu nedenle, HDPE, LLDPE, PVC sırasına göre geomembran astar tabakası ne kadar yumuşak ve esnek olursa, yüzey topoğrafyasının daha şiddetli tepeler ve vadiler göstermesi nedeniyle aşınma o kadar fazla gelişir. Ayrıca, kum danelerinin şekilsel özellikleri, köşeli-sivri parçacıkların geomembran astarının yüzeyine nüfuz edebilmesi ve dolayısıyla yüzey boyunca bir yörünge çizebilmesi nedeniyle daha şiddetli aşındırıcı etkinin harekete geçmesine yol açmıştır. Oysa ki, zirvelerden vadilere ve zirvelere keskin ve pürüzlü geçişlerin sergilendiği LLDPE ve PVC geomembranlar ile karşılaştırıldığında, yüzey topografyası için tepe ve çukurların boyutları ve aralıkları nispeten daha sert geomembran HDPE astar tabakasında küçük ölçekliydi; burada yüzey topografyası keskin köşelere sahip değildi, böylece tepelerden vadilere ve tepelere geçişler karşılaştırıldığında pürüzsüz ve yuvarlaktı. Geomembranların ölçülen yüzey topoğrafyaları için belirlenen ortalama pürüzlülüğün (Ra) hesaplanan değerleri aracılığıyla farklı geomembrane astarların yüzey topoğrafyası değişiminin niceliği, Ra'nın (yani, yüzeysel topografik çeşitliliğin) yük, bağıl yoğunluk, dane şeklinin parçacık sivriliği, ve geomembran astar tabakasının yumuşaklığının artışıyla arttığını ortaya çıkardı.Öğe Comparative analysis on practical implications and evaluation of PVC geomembrane interfaces against particulate materials(Environmental Research & Technology, 2018) Karademir, TanayABSTRACT: An experimental research study including a series of laboratory large displacement interface shear tests between different particulate materials (rounded, angular sands) and smooth PVC geomembranes, and additionally, a series of Shore D Hardness measurements were conducted. The aim of this study is to investigate an easy and quick means of predicting shear resistance/strength of sand-polymer interfaces indirectly from the hardness of the continuum material (i.e. PVC geomembrane) at the interface to establish a comparative analysis between direct test results and indirect practical evaluation through hardness property based on an important interface shear property; friction angle, (?) at peak and residual states measured directly from interface shear tests performed in the laboratory as well as computed indirectly from empirical models developed in the study for the case of different normal loading conditions (i.e. normal stress levels:25, 100, 400 kPa). The results and analysis will be presented throughout the paper demonstrate that the mobilized shear response and the resulting frictional resistance of sand (rounded, angular) – PVC geomembrane interface systems are highly dependent on a combination of loading conditions, geomembrane physical material properties (i.e. hardness) and particulate shape (i.e. angularity/roundness). For direct and indirect assessment of the resultant [?Peak] and [?Residual] values, the comparative analysis showed that a reasonable similarity between the laboratory test results and the indirect analytical assessment analysis is evident from the analogicalness of the experimentally measured values at the predetermined normal stress levels (25, 100 and 400 kPa) to the computed values from the proposed empirical correlation equations proposed in the paper.Öğe Comparison of soil improvement techniques on the development of efficient consolidation response(Murat YAKAR, 2024) Karademir, TanayA comprehensive experimental program including two distinct series of consolidation tests was performed on clay specimens prepared at different dry weight proportions including 0%, 1%, 2.5%, 5%, 7.5%, 10% polypropylene fiber or lime by weight mixed with clayey soil. Fiber inclusion into clay resulted in enhancement of compressive strength characteristics, improvement of hydraulic properties that is an advantage for modification of stability and durability properties of clayey soil under loads. Similarly, the higher hydraulic conductivity of clay resulted that will shorthen duration of consolidation settlement, hence, eventually influence completion of plastic consolidation deformation favorably for soft clays. Lime-treatment on clay specimens showed that the compressibility properties are improved such that the strength of clay against loading enhances, exhibits less consolidation deformation under load owing to increase in lime content. On the other hand, clay becomes highly impermeable, displays substantially larger water-resistant properties because of increased lime mass proportion (i.e. time-extension) in clayey soil that results in prolongation of expulsion of excess porewater pressure from clay due to load application, relevant induced stresses. Fiber-inclusion resulted in exhibiting logarithmic decrement with a mild rate of decline while lime-treatment led to exponential reduction with a sharp rate of drop for compression index (Cc), compressibility coefficient (?v), volume compressibility coefficient (mv). Further, fiber-inclusion stimulated exponential and quadratical increment whereas lime-treatment induced exponential decrement for coefficient of consolidation (cv), hydraulic conductivity (k), respectively. As a result, the Cc, ?v, mv enhanced on the order of within 10 at average of 80% to 90% with a minimum of 70% by value for both fiber-reinforcement and lime-stabilization soil-stabilization techniques. The cv, k improved on the order of within 10 at average of 75% to 85% by value for fiber-reinforcement whereas dis-improved on the order of within 10 at average of 70% to 80% by value for lime-stabilization.Öğe Composite Sand–Clay Infrastructural Soil Fills: Characteristic Consolidation and Hydraulic Properties(Çanakkale Onsekiz Mart University, 2024) Karademir, Tanay; Dışkaya, BurcuIn the design construction of infrastructural projects comprised of geotechnical applications, including composite soil fill layers, compacted sand-clay soil fills are widely preferred as barrier layers, particularly in solid waste landfills, to minimize leakage, to prevent leachate from entering into groundwater. When bentonite clay with high water absorption capacity and low hydraulic conductivity is mixed with sand possessing relatively enhanced frictional properties, greater shear strength capacity, an effective fill material exhibiting low sensitivity to frost, and low volume change in case of wetting, drying can be obtained. On the other hand, when montmorillonite clay is loaded, due to highly critical volumetric contraction or dilation characteristics (high compressibility nature of clay), the soil fill composed of sand-clay will significantly consolidate. This situation may cause differential settlement problems of infrastructural fills employed in geotechnical applications. In this regard, the load conditions (mechanical effects) and the environmental conditions (physicochemical effects) in the field control compressibility characteristics and consolidation properties of sand-bentonite clay mixtures. This will ultimately impact the desired stability conditions of sand-clay soil layers built for constructed infrastructural fill, resulting in a deviation from anticipated performance conditions. To this end, in this study, the specimens of sand-bentonite clay mixtures prepared with different contents of sand-bentonite clay were subjected to one-dimensional consolidation tests to investigate the effect of bentonite content used in the mixture on consolidation behavior, hydraulic properties, and effect of sand amount on rate of consolidation and on resulting compressive strength behavior.Öğe Computer-Automated Triaxial Testing System for Assessing and Mitigating Sample Disturbance in a Natural Clay in the Laboratory(Amer Soc Testing Materials, 2014) Karademir, TanayA computer automation for a manual triaxial cell involved in designing new test instrumentation components and connections and in developing new controller software and supportive hardware for accurate functioning of the system during long test durations was undertaken to run high-quality, sophisticated triaxial tests for measuring the stressstrain properties of clays. For validation and further evaluation of the developed computerautomated triaxial testing system, a laboratory testing program was performed to investigate the effects of sample disturbance on laboratory-measured clay soil behavior and the mitigation of disturbance effects in the laboratory using two reconsolidation methods, the stress history and normalized soil properties (SHANSEP) method and the recompression method. Computer-automated triaxial tests were performed on specimens of Boston blue clay (BBC) from a test site (Newbury, MA) sampled using a Sherbrooke-type block sampler. The test results from the laboratory testing program are presented, including for (i) onedimensionally consolidated undrained compression (CKoUC) tests on both normally consolidated (NC) and mechanically overconsolidated (OC) specimens using the SHANSEP method and (ii) anisotropically consolidated undrained compression (CAUC) tests using the recompression method. The CKoUC(NC) tests were performed to provide baseline SHANSEP data, and results were compared between CKoUC(OC) SHANSEP and CAUC recompression tests.Öğe Elevated Temperature Effects on Geotextile-Geomembrane Interface Shear Behavior(Asce-Amer Soc Civil Engineers, 2021) Karademir, Tanay; Frost, J. DavidThe performance of geosynthetic layered systems during their service life in terms of interface shear behavior and strength properties is of major importance in certain geotechnical applications. The interfaces between geotextiles and geomembranes in landfill applications are subject to temperature changes. In this respect, interface shear behavior requires assessment of the engineering strength properties of the components, both independently and collectively, at different temperatures. To this end, an extensive research study was undertaken to investigate temperature effects on the interface shear behavior between needle-punched nonwoven (NPNW) polypropylene (PP) geotextiles and both smooth polyvinylchloride (PVC), as well as smooth and textured high-density polyethylene (HDPE) geomembranes. A temperature-controlled chamber (TCC) was utilized to simulate the field conditions at elevated temperatures and evaluate shear displacement and frictional response mobilized at different temperatures. The physical laboratory testing program consisted of interface shear tests between material combinations found in landfill applications under a range of normal stress levels from 10 to 400 kPa and at a range of ambient temperatures from 21 degrees C to 50 degrees C. An increase in temperature from the standard laboratory test temperature of 21 degrees C to an equivalent in situ temperature of 50 degrees C increases the peak and postpeak interface friction values by a minimum of 14%. For selected combinations of materials, the amount of increase can be in excess of 20% and as high as 22%. Consequently, interface shear behavior determined at room temperature yields interface friction values that are conservative at higher temperatures.Öğe Micro-mechanical properties of geotextile fibers: measurement and characterization at cold environmental conditions(Research on Engineering Structures and Materials, 2021) Karademir, TanayABSTRACT: One of the most important properties of a fabric (geotextile) and also one of the focus areas of the current research study is its tensile strength, and thus, mechanical properties (modulus, resilience, strength, toughness). To this end, the mechanical properties of the geotextiles must properly be evaluated at the “macro-scale” as well as at the “micro-scale” as they are fibrous synthetic materials including polymeric fibers as well as significant volume of void space. As being a polymer, the mechanical behavior of the geotextile micro-fibers is highly dependent on the ambient conditions including particularly the temperature. In light of this, the tensile behavior of geotextile single micro-fibers was characterized by performing micro-mechanical tensile tests at “micro-scale” level at different cold temperature conditions using Dynamic ThermoMechanical Analyzer (DMA) to measure the developed “micro-scale” tensile stress – strain behavior of geotextile micro-fibers. The results examined from the influence of micro-mechanical properties of polymeric fibers on the observed temperature dependent stress-strain curve were used to determine the modulus of elasticity (E), modulus of resilience (UR), ultimate tensile strength (?max), amount of plastic strain (?p), toughness (UT), rupture strength (?R) for the polypropylene (PP) micro-fiber of needle-punched nonwoven (NPNW) geotextile and the variation in those important mechanical properties with a change in ambient temperature conditions. The experimental results show that the mechanical properties of the PP fibers do not remain constant within the common range of cold temperatures (-10 °C – 21 °C) found in typical civil engineering applications such that the temperature change was found to be an important factor affecting the PP fiber micro-mechanical properties such as modulus, strength, toughness and plastic elongation. Therefore, the test results provide an index of behavior at “micro-scale” level for the polymeric geotextile single fibers at cold temperature conditions.Öğe Micro-scale tensile properties of single geotextile polypropylene filaments at elevated temperatures(Elsevier Sci Ltd, 2014) Karademir, Tanay; Frost, J. DavidGeotextiles are porous and fibrous materials that consist of randomly oriented and isotropically distributed long filaments which vary in terms of spatial distribution, curvature, orientation, size, and mass density. The heterogeneous internal structure of geotextiles constituted from individual/discrete fibers and having different micro-structure and macro-structure properties are prone to exhibit dissimilar tensile stress-strain behavior (i.e. progressive versus reactionary) as well as showing favorable versus adverse response to varied experimental conditions such as temperature and strain rate change when tested at macro scale as opposed to micro-scale level. To this end, in order to evaluate thermo-tensile strength properties as well as to characterize tensile extension behavior of single geotextile filaments at micro-scale level, micro-mechanical tensile tests were performed at different temperatures using a Dynamic Thermo-Mechanical Analyzer (DMA) on single filaments extracted from polypropylene needle punched nonwoven geotextile. Various test temperatures between 21 degrees C and 50 degrees C were chosen to represent and simulate the wide range of temperatures encountered in the field for geotechnical applications such as landfill base liners. The paper also presents a statistical analysis of the results of the test program to provide a basis for comparison of inherent filament variability. (C) 2014 Elsevier Ltd. All rights reserved.Öğe Shear response and frictional properties of soil mixtures at different dry weight proportions(Yildiz Technical Univ, 2022) Karademir, TanayOn a specific purpose to investigate and evaluate an important mechanical property of natural soil mixtures being shear response and frictional characteristics, an extensive laboratory experimental program has been conducted that consisted of a series of direct shear tests on various soil mixtures, including sand (S), silt (M) and clay (C), at different dry weight proportions [(i) S:100% - M:0% - C:0%; (ii) S:50% - M:50% - C:0%; (iii) S:50% - M:0% - C:50%; (iv) S:50% - M:25% - C:25%]. The experimental findings of the testing program have shown that the measured values of two crucial engineering design parameters such as the peak (t(peak)) as well as the residual (tresidual) shear strengths for the soil mixtures are strongly influenced by the present soil type such that the detected values of tpeak, tresidual increase with an increase in sand content in the mixture whereas the attained values of t(peak), t(residual) decrease with an increase in clay content in the mixture. Further, adding silt into sand-clay mixture improves strength characteristics such that the values of tpeak, tresidual become greater. On the other hand, adding silt into pure sand diminishes frictional resistance such that the values of t(peak), t(residual) become lower. Consequently, it is seen that soil particle size (i.e. grain size) plays an important role on the shear strength behavior of the natural soil mixtures. Moreover, the displacement (dpeak) required to reach peak shear strength (t(peak)) was also determined as a result of the direct shear tests. As such, the detected values of dpeak become larger with higher clay content available in the mixture, while the obtained values of dpeak become smaller with higher sand content existing in the mixture. Therefore, it is concluded that the higher the clay content, the mixture exhibits relatively more ductile shear behavior, whereas the higher the sand content, the mixture displays relatively more brittle shear response.
