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Öğe Compaction Properties of Soil Composite Fills: Sand, Silt, Clay and Polypropylene Fiber Mixtures(Springer Science and Business Media Deutschland GmbH, 2023) Karademir, T.A laboratory experimental program including a series of compaction tests on various soil composite fill samples prepared by using sand, silt, clay and polypropylene (PP) fiber at different dry weight proportions was performed. As a result of the tests, the compaction curves were developed for distinct soil composite fill samples so as that the two most crucial and critical compaction engineering design parameters: maximum dry unit weight (?d-max) and optimum moisture content (wopt) were determined. The change in the detected values of ?d-max and wopt was investigated by addition of; (i) silt, (ii) clay, (iii) PP fiber, (iv) or selected two of them, (v) or all of them into sand, and thus, the behavior in those two important compaction characteristics (?d-max, wopt), that are decisive properties in design and construction of soil fill infrastructures, was identified for various different soil composite fill samples including different materials studied. It was seen that the ?d-max decreases, whereas, the wopt increases as a result of adding silt and/or clay into pure sandy soil. The greater change in the values was observed for clay inclusion compared to that of silt. On the other hand, the inclusion of PP fiber into sandy soil resulted in an increase in the measured values of ?d-max, while a decrease in the detected values of wopt. Consequently, the PP fiber served a relative advantage in comparison to the two other materials (silt, clay) by facilitating enhanced compaction properties for the improvement of the characteristics of soil composite fill under loading, and thereby, enabling highly densification or more desirable compaction of the fill not only at larger ?d-max but also at lower wopt so as to better comply with common design criteria in practice for the application of compaction procedure in the field during construction as well as to achieve higher bearing capacity (larger load-carrying resistance), and hence, superior performance during operation of the infrastructure built from this soil composite fill. © The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd 2023.Öğe Comparative analysis on practical implications and evaluation of PVC geomembrane interfaces against particulate materials(Yildiz Technical University, 2018) Karademir, T.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. © Yildiz Technical University, Environmental Engineering Department. All rights reserved.Öğe Counterface soil type and loading condition effects on granular/cohesive soil – Geofoam interface shear behavior(Murat Yakar, 2024) Karademir, T.Soil – geofoam interfaces have been studied through an extensive experimental program by performing multiple series of interface shear tests using two different granular soils (i.e. beach sand and construction material sand) and one cohesive soil (i.e. bentonite clay) as well as a soil mixture containing 75% sand and 25% clay by dry weight at distinct loading conditions (i.e. normal stresses (?): 25, 100, 250; low, moderate, high loading conditions, respectively). Using the shear stress versus horizontal displacement curves obtained, some important engineering design parameters including peak shear stress, residual shear stress, interface sensitivity (i.e., peak/residual ratio) and displacement required to reach peak stress have been determined and the variations in those interface mechanical properties as a function of loading condition and counterface soil type have been investigated. It was shown that the peak as well as residual shear stresses increased with an increase in normal stress for all the interface systems tested. Further, the granular soil (sand) interfaces demonstrated relatively larger frictional strengths (both peak and residual) as compared to both the cohesive soil (clay) interface and the sand/clay admixture soil interface. Additionally, the higher the angularity of granular soil particles became, the larger the interface shear strengths (peak and residual), when sheared against geofoams, developed in light of experimental results attained as a result of interface shear tests on different material combinations. For comparison, the detected peak strength at average for the construction material sand, the beach sand, and the sand/clay admixture soil interfaces as compared to the bentonite clay interface were improved 59.8%, 43.4%, and 20.3%, respectively. Additionally, the detected residual strength at average for the construction material sand, the beach sand, and the sand/clay admixture soil interfaces as compared to the bentonite clay interface were improved 53.9%, 28.6%, and 15.4%, respectively. © Author(s) 2024.Öğe Lime stabilization of clayey landfill base liners: Consolidation behavior and hydraulic properties(Yildiz Technical University, 2022) Karademir, T.Lime soil treatment is a chemical process in which lime (quicklime, hydrated lime or lime slurry) is mixed with the in place subgrade soil and a chemical reaction takes place. The lime reacts with the clay particles in the soil to create a cementitious matrix. The design of landfill base liners including a clay layer as a fluid barrier (i.e. water-resistant impervious layer) requires a neat engineering approach considering, in particular, consolidation behavior as well as hydraulic properties of the clay contained. For sake of safe and stable design of such baseliners under the landfills, the reduction of consolidation settlement in clay when subjected to the accumulated waste load (i.e. superposed action) during operation as well as the accomplishment for ensuring the waterproof of those composite base liners (comprised of multiple different layers) not to allow the penetration of the contaminated water - produced as a result of exothermic reactions occurring in the waste body in landfills – by enabling enhanced isolation from the natural ground is of importance. In light of this, in order to address those two most important design concerns (i.e. Consolidation and Hydraulic Properties of Clay) as well as to in an attempt to develop an enhanced clay layer system for landfill baseliners that has a greater bearing capacity (i.e. load resistance), and hence, more robust against settlements, and additionally, possessing improved hydraulic properties by being relatively more water-resistant and greatly impermeable, a series of consolidation tests were performed in the laboratory at different lime contents (lime/lime-clay mixture proportions by weight: 0%, 10%, and 20%) on clay specimens to investigate the stabilization and improvement of clayey landfill baseliners. Lime treatment on clay specimens has shown as a result of the experimental program that the strength of clay against loading improves, and further, exhibits less vertical deformation (settlement) under the load owing to an increase in lime content. Moreover, the clay becomes highly impermeable and displays substantially larger water-resistant properties because of increased lime mass proportion in clayey soil. The findings of the experimental program demonstrate that lime stabilization of the clayey soils in landfill baseliners will benefit the bearing capacity and the imperviousness (water tightness) engineering design properties as compared to standard composite multi-layered landfill baseliner systems. Copyright 2022, Yıldız Technical University.Öğe Shear-induced changes in smooth geomembrane surface topography at different ambient temperatures(Ice Publishing, 2016) Frost, J. D.; Karademir, T.The shear strength of particulate material-smooth geomembrane interfaces results predominantly from ploughing and/or sliding of the particles at the interface. The relative contribution of particle sliding and ploughing for a given smooth geomembrane surface is principally a function of relative material hardness, particle angularity, and normal stress. The relative material hardness is ambient temperature dependent since the geomembrane is polymer based. When ploughing occurs at any temperature, the geomembrane surface wears, resulting in altered surface topography and different interface strength. This paper summarises the results of a study that quantified changes in the surface roughness of geomembranes as a function of ambient temperature, normal stress, and particle angularity. Surface roughness measurements were made on both virgin and post-shear smooth geomembrane specimens using a stylus profilometer to quantify the extent of wear resulting from shearing against different counterface materials at different temperatures under different normal stresses. Increased ambient temperature and particle angularity significantly increased the geomembrane surface roughness and provided quantitative insight into the wear mechanisms at granular material-smooth geomembrane interfaces.