Yazar "Demir, Ahmet" seçeneğine göre listele

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    Evaluating of geosynthetics reinforced road base with plate loading tests
    (Pamukkale Univ, 2021) Ok, Bahadir; Demir, Ahmet; Sarici, Talha; Ovali, Mesut
    The use of geosynthetics as reinforcement for the base layer of flexible pavement systems has grown steadily over the past thirty years. Although geosynthetic reinforcements can lead to improved pavement performance, the specific conditions or mechanisms that govern the reinforcement are unclear, largely remaining unidentified and unmeasured. In this study, the assessment of the effect of geogrids on the roads that is reinforced granular fill layer over soft clay soil, section's ability to support before and after traffic loads were investigated using plate loading tests in situ. The results of the field tests show that geosynthetic reinforcement as is an effective method in reducing deformation and repairing granular fill layer overlying soft foundations.
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    Evaluation of Granular Fill Layer Underlain by Soft Clay Soil Using Large Scale Cyclic Plate Loading Tests
    (Springer Int Publ Ag, 2023) Demir, Ahmet; Ok, Bahadir; Sarici, Talha
    In general, granular fill materials are widely used to construct new pavement and rehabilitate old pavement. For pavement design, it is essential to know the basic characteristics, such as the permanent deformation behavior of these materials. Considering this phenomenon, this study aims to explain the performance of granular fill layers in pavement systems using cyclic plate load tests. For this purpose, a large-scale cyclic plate load test facility, also known as pavement model testing (PMT), was developed to investigate the permanent deformation characteristics of the pavement structure. To conduct experiments, a standard pavement structure was built with granular fill layers on top of a soft clay subgrade and a geotextile between the subgrade and the base layer. The PMT was used to apply a 40 kN cyclic load through a steel plate with a 305 mm diameter for up to 10,000 cycles after the pavement structure was built. A total of four tests were carried out to evaluate the effects of the granular fill layer's thickness on the pavement's permanent deformation. Furthermore, an analytical solution was developed for the fill layer thickness using the test results. Additionally, the outcomes of some previous studies in the literature were compared to the ones that were obtained. The results of this study indicate that the permanent deformations of the pavement structure and the subgrade increased with the number of load cycles. The permanent deformations began to limit at 3000 cycles when the fill layer thickness was 20 cm, but it was observed that deformations did not limit at 3000 cycles when the fill layer thickness increased to 45 cm. Also, the permanent deformations decreased by two times when the granular fill layer thickness doubled appropriately.
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    Evaluation of Rockfill Stabilized-Geosynthetics Reinforced Road Base with Repeated Plate Loading Tests
    (Mdpi, 2024) Demir, Ahmet; Ok, Bahadir; Sarici, Talha
    In this study, the performance of unpaved road sections over soft clay soil geosynthetic-reinforced and stabilized with rock fill layer was evaluated using repeated plate loading tests. A total of 10 field tests were carried out using a circular model rigid plate with a diameter of 0.30 m. The parameters investigated included the location and type of geosynthetics and loading conditions (number of loading cycle and traffic loading condition). Based on the test results, the least deformation was observed in the rockfill section. The geocell placed at a depth of one-third thickness of the granular fill layer from the top showed improved performance and was more effective as compared with other geosynthetic reinforcements. However, for granular fill geosynthetic-reinforced or stabilized with rock fill layer, the results demonstrate an improvement in the rutting performance of the pavement and the definite trend of increasing reloading elastic modulus, depending on the traffic loading situation. It has been also observed that the use of geocell or geogrid reinforcement in granular fill layer or more rigid rockfill layer provides an important increase in the modulus improvement ratio (MIR) by at least 36%, 45% and 60% compared to the granular fill section, respectively.
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    Field Test of Circular Footings on Reinforced Granular Fill Layer Overlying a Clay Bed
    (Amer Soc Testing Materials, 2012) Laman, Mustafa; Yildiz, Abdulazim; Ornek, Murat; Demir, Ahmet
    The ultimate bearing capacity and settlement of a circular shallow rigid plate on compacted granular fill layer with and without geogrid reinforcement overlying on natural clay deposit exhibiting low bearing capacity and large settlement have been investigated. A total of 15 field tests were carried out using a circular model rigid plate with a diameter of 0.90 m. This study has been initially directed to evaluate the beneficial effects of the compacted granular fill layer on natural clay deposit for the shallow rigid plate performance. Then, the reinforcing effect of the top granular fill layer with horizontal layers of welded geogrid reinforcement on the bearing capacity and settlement has been studied. Parameters of the testing program include granular fill thickness, depth of first reinforcement, vertical spacing of reinforcement layers, and number of reinforcement layers. Bearing capacity ratio (BCR) and percentage reduction in settlement (PRS) were defined to evaluate improvement performance. Based on the test results, the effect of the granular fill and welded geogrid reinforcement on the bearing capacity and settlement are discussed. The results indicate that the use of granular fill layers over natural clay soils has considerable effects on the bearing capacity and settlement characteristics. The construction of granular fill layer with welded geogrid reinforcement over clay deposit helps in redistributing the applied load to a wider area. It has been observed that the use of welded geogrid reinforcement in granular fill layer provides additional improvement of bearing capacity and provides reduction in settlement of the rigid plate up to 80 and 60 %, respectively.
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    Field test of circular footings on reinforced granular fill layer overlying a clay bed
    (2012) Laman, Mustafa; Yildiz, Abdulazim; Ornek, Murat; Demir, Ahmet
    The ultimate bearing capacity and settlement of a circular shallow rigid plate on compacted granular fill layer with and without geogrid reinforcement overlying on natural clay deposit exhibiting low bearing capacity and large settlement have been investigated. A total of 15 field tests were carried out using a circular model rigid plate with a diameter of 0.90 m. This study has been initially directed to evaluate the beneficial effects of the compacted granular fill layer on natural clay deposit for the shallow rigid plate performance. Then, the reinforcing effect of the top granular fill layer with horizontal layers of welded geogrid reinforcement on the bearing capacity and settlement has been studied. Parameters of the testing program include granular fill thickness, depth of first reinforcement, vertical spacing of reinforcement layers, and number of reinforcement layers. Bearing capacity ratio (BCR) and percentage reduction in settlement (PRS) were defined to evaluate improvement performance. Based on the test results, the effect of the granular fill and welded geogrid reinforcement on the bearing capacity and settlement are discussed. The results indicate that the use of granular fill layers over natural clay soils has considerable effects on the bearing capacity and settlement characteristics. The construction of granular fill layer with welded geogrid reinforcement over clay deposit helps in redistributing the applied load to a wider area. It has been observed that the use of welded geogrid reinforcement in granular fill layer provides additional improvement of bearing capacity and provides reduction in settlement of the rigid plate up to 80 and 60 %, respectively. Copyright © 1996-2012 ASTM.
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    Investigation of the construction and demolition materials reinforced by geosynthetics
    (Emerald Group Publishing Ltd, 2023) Ok, Bahadir; Sarici, Talha; Demir, Ahmet; Talaslioglu, Tugrul; Yildiz, Abdulazim
    Many researchers suggest using construction and demolition materials in engineering applications (C & D) rather than virgin aggregates (VA). However, the engineering properties of the C & D tend to be poorer than those of the VA. This study presents the results of plate loading tests performed on unpaved roads with the C & D, reinforced by different types of geosynthetics on the soft subgrade. As part of these tests, the effects of some geosynthetics' parameters such as (1) the embedment depth, (2) height and pocket opening of geocell, (3) the embedment depths and number of geogrids, (4) the distance between geogrids, and (5) the stiffness of geotextile on the bearing capacity of the unpaved road were investigated. Besides, the same plate loading test was also conducted on an unpaved road built by the VA. As a result of this study, although the performance of the C & D was determined to be less than that of the VA, it was concluded that the C & D performed well enough to be used as an alternative to the VA on unpaved roads. Besides, with a very small number of geosynthetics, it was determined that the C & D could have a better performance than that of the VA.
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    Large scale tests for geogrid reinforced unpaved roads
    (Korean Geosynthetics Society, 2018) Demir, Ahmet; Sarici, Talha; Ok, Bahadır; Demir, Birol; Komut, Muhammet; Comez, Senol; Mert, Aykan
    This paper intends to present and discuss the performance of geogrid reinforced and unreinforced granular fill layer in unpaved road systems using large scale cyclic plate load tests. A large scale cyclic plate load test facility was developed to study the permanent deformation (rutting) characteristics. Cyclic loads at a constant frequency were applied on geogrid reinforced and unreinforced laboratory unpaved road sections through a rigid circular plate. An unpaved road structure consisting of granular road material over a soft clay soil subgrade was made. To prepare reinforced sections, geogrid was placed within the granular road material at the desired location. Also, geotextile was placed at the interface between road material and soft clay soil subgrade for separation. The model of unpaved road structure was constructed in a steel tank. A total of 5 large scale laboratory tests were conducted to evaluate the effects of geogrid reinforcement. The test results indicated that considerable improvement in bearing capacity was observed when geogrid was placed within the granular road material at all levels of deformations. Permanent deformation (rutting), plastic surface deformation and vertical stress development under cyclic loading was greatly reduced with the inclusion of geogrid. The optimum placement position of geogrid was found at a depth of one-third of the plate diameter below the surface. Copyright © 11th Inter. Conf. on Geos. 2018, ICG 2018. All rights reserved.
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    Prediction of bearing capacity of circular footings on soft clay stabilized with granular soil
    (Japanese Geotechnical Soc, 2012) Ornek, Murat; Laman, Mustafa; Demir, Ahmet; Yildiz, Abdulazim
    The shortage of available and suitable construction sites in city centres has led to the increased use of problematic areas, where the bearing capacity of the underlying deposits is very low. The reinforcement of these problematic soils with granular fill layers is one of the soil improvement techniques that are widely used. Problematic soil behaviour can be improved by totally or partially replacing the inadequate soils with layers of compacted granular fill. The study presented herein describes the use of artificial neural networks (ANNs), and the multi-linear regression model (MLR) to predict the bearing capacity of circular shallow footings supported by layers of compacted granular fill over natural clay soil. The data used in running the network models have been obtained from an extensive series of field tests, including large-scale footing diameters. The field tests were performed using seven different footing diameters, up to 0.90 m, and three different granular fill layer thicknesses. The results indicate that the use of granular fill layers over natural clay soil has a considerable effect on the bearing capacity characteristics and that the ANN model serves as a simple and reliable tool for predicting the bearing capacity of circular footings in stabilized natural clay soil. (C) 2012. The Japanese Geotechnical Society. Production and hosting by Elsevier B.V. All rights reserved.
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    Uplift response of multi-plate helical anchors in cohesive soil
    (Techno-Press, 2015) Demir, Ahmet; Ok, Bahadir
    The use of helical anchors has been extensively beyond their traditional use in the electrical power industry in recent years. They are commonly used in more traditional civil engineering infrastructure applications so that the advantages of rapid installation and immediate loading capability. The majority of the research has been directed toward the tensile uplift behaviour of single anchors (only one plate) by far. However, anchors commonly have more than one plate. Moreover, no thorough numerical and experimental analyses have been performed to determine the ultimate pullout loads of multi-plate anchors. The understanding of behavior of these anchors is unsatisfactory and the existing design methods have shown to be largely inappropriate and inadequate for a framework adopted by engineers. So, a better understanding of helical anchor behavior will lead to increased confidence in design, a wider acceptance as a foundation alternative, and more economic and safer designs. The main aim of this research is to use numerical modeling techniques to better understand multi-plate helical anchor foundation behavior in soft clay soils. Experimental and numerical investigations into the uplift capacity of helical anchor in soft clay have been conducted in this study. A total of 6 laboratory tests were carried out using helical anchor plate with a diameter of 0.05 m. The results of physical and computational studies investigating the uplift response of helical anchors in soft clay show that maximum resistances depend on anchor embedment ratio and anchor spacing ratio S/D. Agreement between uplift capacities from laboratory tests and finite element modelling using PLAXIS is excellent for anchors up to embedment ratios of 6.