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    An experimental study on improvement of cohesive soil with eco-friendly guar gum
    (Brazilian Soc Soil Mechanics & Geotechnical Engineering, 2021) Bagriacik, Baki; Ok, Bahadir; Kahiyah, Mustafa Tahseen Mohamed Ali
    Recently, the demand for environmentally friendly products has been increasing worldwide. In this study, the improvement of cohesive soil with a biopolymer material (Guar Gum), which is a type of additive and organic, environmentally friendly, is investigated. For this purpose, various laboratory tests have been conducted on the biopolymer-added soils, including the compaction test, the Atterberg limits test, and the unconfined compressive strength test. The samples for tests have been prepared that the biopolymer has been mixed with the soil in three different proportions to determine the optimum mixing ratio. Also, in the biopolymer-added soils, some samples have been cured at varying times to determine the effect of curing periods on their strength. For comparison, the tests performed on improved soils have been also carried out on the untreated cohesive soil. For a comprehensive evaluation, scanning electron microscopy analyses (SEM analyses) was carried out on some samples. On the other hand, X-ray fluorescence analysis (XRF analysis) was performed to have an idea about the composition of the cohesive soil. Consequently, the biopolymer additive material has improved the geotechnical properties of the cohesive soil in all mixing ratios and curing times. Moreover, the optimum mixing ratio has been obtained at 1% according to the results of tests.
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    An Experimental Study on the Usability of Reclaimed Asphalt Pavements or Waste Bricks in the Stone Columns
    (Springer Science and Business Media Deutschland GmbH, 2024) Sarici, Talha; Ok, Bahadir; Akbulut, Nurullah; Cenk, Ahmet Haydar
    This study presents experiments to find out if recycled asphalt pavements (RAP) or waste bricks (WB) can be used instead of natural aggregates (NA) in the stone columns that are used to increase bearing capacity and speed up consolidation settlement. The first step in this research was to get RAP, WB, and NA, then figure out a suitable gradation and unit weight for stone columns, and lastly do tests in the lab, such as pycnometer, minimum and maximum dry unit weights, water absorption, California bearing ratio (CBR), aggregate impact value (AIV), and large-scale direct shear tests. In order to perform CBR, AIV, and large-scale direct shear tests, it was necessary to find the unit volume weight in the stone column. Therefore, the model tests were conducted in a steel tank. The tank was filled with cohesive soil, so that soft soil conditions were created. And then, the stone columns with a diameter of 5 cm were built using RAP, WB, and NA in the middle of the soft soil. Thus, the unit weight values of RAP, WB, and NA were determined according to the amount of material used for the stone column. The results show that RAP and WB could be an alternative to NA for the stone column, although their strengths were lower than those of NA according to the shear strength parameters. However, it was thought that these waste aggregates should be used by improving their insufficient properties, such as water absorption and crushing behavior. © The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2024.
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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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    Evaluating the usability of recycled aggregates as fill materials depending on the composition and strength of their grains
    (Higher Education Press, 2024) Ok, Bahadir; Colakoglu, Huseyin
    While recycling is a topic of contemporary relevance, there is a scarcity of research on the engineering characteristics of construction and demolition wastes with different levels of grain strength and composition of debris, which impose constraints on their potential for reuse. This study aims to increase the use of recycled aggregates in fillings, addressing a gap in the literature. For this purpose, large-scale direct shear and California bearing ratio tests were conducted on nine diverse recycled aggregates from different construction works. The test outcomes were compared to those obtained from natural aggregates (NA) to draw a meaningful conclusion. The impact of the specimens' water content and relative density on the findings was discussed. Results demonstrated that the shear strength of recycled aggregates is significantly affected by the compressive strength of the concrete within the recycled aggregates. Besides, increasing the percentage of NA or relative density improved the specimen's shear strength. On the other hand, it was determined that the high water content of the crushed bricks reduced the fill's quality. As a result of the study, equations were suggested for use in filling design.
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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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    Evaluation of the geogrid-various sustainable geomaterials interaction by direct shear tests
    (Techno-Press, 2023) Ok, Bahadir; Colakoglu, Huseyin; Dagli, Umud
    In order to prevent environmental pollution, initiatives to increase the sustainability of resources are supported by society. However, the performance of recycled materials does not generally match that of natural materials. This study looks into the use of geogrid to improve various types of recycled aggregates. For this purpose, five different recycled aggregates were created by recycling wastes from the construction industry. Besides, direct shear tests (DS tests) were carried out on these recycled aggregates to determine their shear strengths. Following that, a triaxial geogrid was placed in the recycled aggregates to provide reinforcement, and the DS tests were conducted on the reinforced recycled aggregates. The results of the tests were also compared to those of tests performed on natural aggregates (NA). In conclusion, it was found that the recycled aggregates have lower shear strengths than the NA. Nonetheless, when reinforced with geogrid, the shear strength of the recycled concrete aggregates (RCA) and construction and demolition wastes (CDW) exceeded that of the NA. Furthermore, the geogrid reinforcement increased the shear strength of the recycled crushed bricks (CB), though not to the level of the NA. © 2023 Techno-Press, Ltd.
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    Experimental investigation of deformation behavior of geocell retaining walls
    (Techno-Press, 2021) Altay, Gokhan; Kayadelen, Cafer; Canakci, Hanifi; Bagriacik, Baki; Ok, Bahadir; Oguzhanoglu, Muhammed Ahmet
    Construction of retaining walls with geocell has been gaining in popularity because of its easy and fast installation compared to conventional methods. In this study, model tests were conducted by constructing the geocell retaining wall (GRW) at a constant height (i.e., 90 cm) and using aggregate as an infill material at four different configurations and two different surface angles. In these tests, a circular footing was placed behind the walls at different lateral distances from the wall surface and loaded monotonically. Subsequent to this vertical loading being applied to the footing, horizontal displacements on the GRW surface were measured at three different points. The performance of Type 4 GRW exceeded the other three types of GRW, with the highest lateral displacement occurring in Type 4 GRW at approximately 0.67 % of wall height. In addition, the results of these tests were compared with theoretical approaches widely accepted in the literature. The stress levels reached beneath the footing were found to be compatible with theoretical results.
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    Geotechnical properties of recycled construction and demolition materials for filling applications
    (Elsevier, 2020) Ok, Bahadir; Sarici, Talha; Talaslioglu, Tugrul; Yildiz, Abdulazim
    Modern societies make a hard effort to improve the sustainability of resources due to enhanced environmental sensitivities in nowadays. This paper investigates the usability of recycled construction and demolition materials as an alternative to virgin aggregates in geotechnical applications such as the filling. The physical and geotechnical properties of recycled construction and demolition materials were determined by laboratory tests (i.e. sieve test, flatness test, Los Angeles abrasion test, water absorption test, pycnometer test, modified compaction test, California bearing ratio test, unconfined compressive strength test and resilient modulus test) and a comprehensive laboratory evaluation was carried out. Moreover, similar tests were conducted with a type of high quality virgin aggregate material frequently used in fillings. The results of the tests conducted on construction and demolition materials were compared with results of the tests conducted on both virgin aggregate and different recycled aggregates which are accepted as an alternative to virgin aggregates used in the filling in the literature. Results of the tests conducted on construction and demolition materials were also evaluated according to the limit values in technical specifications of highway administrations of various countries. As a result of this study, it has been concluded that construction and demolition materials can be a good alternative to virgin aggregate used in the filling provided that it is taken measure against excessive water absorption value.
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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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    Model studies on recycled whole rubber tyre reinforced granular fillings on weak soil
    (Pontificia Univ Catolica Chile, Escuela Construccion Civil, 2022) Geckil, Tacettin; Sarici, Talha; Ok, Bahadir
    The main purpose of this study is to determine the stress-strain behaviour of a rigid circular footing placed on recycled rubber tyre-reinforced granular filling built on weak soil. For this purpose, model plate loading tests were carried out on reinforced/unreinforced granular filling built with natural aggregates (NA) or construction and demolition waste materials (CDW). The rubber tyre used for reinforcement has become a waste material by completing its service life but it has retained its typical cylindrical shape. In model plate loading tests, the effects of the granular fillings, the type of fillings material and the placement of whole rubber tyre and/or geotextile in the granular fillings were investigated. Depending on the results of tests, it was determined that the bearing capacity was increased by reinforcing with the rubber tyre and/or the geotextile. Furthermore, it was specified that the highest increase in bearing capacity was occurred case of by reinforcing with the geotextile together with the rubber tyre of the granular filling. The CDW and the NA fills reinforced with geotextile together with the rubber tyre increased the bearing capacity of weak soils by 6.59 and 8.49 times, respectively, for the 5% deformation ratio. On the other hand, it was reported that although the bearing capacity of the NA was higher than that of the CDW, the bearing capacity of the reinforced CDW approached that of the NA.
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    Seismic performance of recycled aggregate-filled cantilever reinforced concrete retaining walls
    (Sage Publications Ltd, 2019) Saribas, Ilyas; Ok, Bahadir
    This study investigates the effects of the use of two different types of recycled aggregates with known characteristics as backfill materials in newly built cantilever reinforced concrete retaining walls on the seismic performance of the walls. The physical properties of the recycled aggregates used as backfill materials were determined using aggregate tests. Subsequently, analytical studies for the reinforced concrete retaining walls containing recycled aggregates in the amounts of 25%, 50%, 75%, and 100% were performed under seismic and static loads and the results were compared with those obtained for the retaining walls containing 100% natural aggregate as the backfill material. The experimental and analytical studies showed that the internal friction angles and effective ground acceleration coefficients significantly affected the overturning moment and total active pressure values of the retaining walls. The results led to the conclusion that recycled aggregates can be partially or completely used as the backfill material in retaining walls. Moreover, the current conventional calculation methods for design and analysis were proven valid for the reinforced concrete retaining walls containing recycled aggregates as backfill materials.
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    Soil-geogrid interaction: The shear zone thickness of seafloor sediments with geogrid compared to filling materials
    (Taylor & Francis Inc, 2024) Ok, Bahadir; Aker, Altan
    In geotechnical applications close to marine areas, using soil with rounded gravel that waves have left on the seafloor as fill material can help ensure the sustainable use of natural resources. However, typical fill materials have more shear strength than rounded sediments, but geogrids can solve the issue. Nevertheless, it is not well known how the grains' shape factors will affect the soil-geogrid interlocking mechanism and how the soil-geogrid interlocking based on grain shape will vary in the soil above and below the geogrid. This study aims to address the ambiguities specified. Therefore, three soil specimens were acquired, and the grains' shape parameters were determined using image processing. Subsequently, soil specimens were tested using large-scale direct shear (LSDS) and California Bearing Ratio (CBR) tests. Besides, LSDS tests were conducted by placing the geogrid at the shear surface, at different depths beneath the shear surface, and at varying levels above the shear surface to assess the soil-geogrid interaction distance. The findings showed that soil with seafloor gravels, using geogrid, could have the same shear strength as soil with crushed aggregates. Also, the highest shear strength was achieved when the geogrid was located below the shear surface by the maximum grain diameter.
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    The Behavior of Continuous Foundations with Sustainable Concrete and Soil Under Monotonic Loads
    (TUBITAK, 2022) Saribas, Ilyas; Ok, Bahadir
    Due to the renovation of structures, natural disasters, and regional-global wars, construction and demolition waste material is generated. The remediation of these wastes by recycling and reusing activities is one of recent most common research topics. Recycled aggregates are obtained through the recycling activities of these waste materials. In the literature, detailed studies have been carried out to use recycled aggregate as a sustainable product in producing new concrete or as a filling material. Besides, the scope of these studies continues to expand. In this comprehensive study, the structural behavior of the soil-structure interaction problem under the monotonic load, which is assumed to be produced with sustainable materials, was investigated. Furthermore, the concrete properties of these foundation beams representing the superstructure were considered with conventional and sustainable concrete. The characteristics of the filling materials were regarded with five different sustainable materials. The deflection, rotation, bending moment, shear force, and spring forces are obtained based on the numerical simulation. The sustainable soil-structure interaction problem results were compared with the conventional counterparts. Based on the comparisons, it was observed that the deflection, rotation, bending moment, shear force, and spring forces that occur in the foundation beam are affected by sustainable material properties. © 2022, TUBITAK. All rights reserved.
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    The numerical simulation of soil-structure interaction containing sustainable materials
    (Ice Publishing, 2022) Saribas, Ilyas; Ok, Bahadir
    As a result of urban transformation activities, natural disasters, regional and global wars, billions of tonnes of waste concrete occur. Therefore, the remediation process of waste concrete is one of the critical research topics of recent years. The sustainability concept provides a primary bridge between the demand for natural concrete material and the remediation process of waste concrete. Recycled aggregate and recycled concrete aggregate, which may be named sustainable materials, are obtained by the recycling process of waste concrete. Many experimental and numerical studies have been conducted in recent years to show that this sustainable material is an alternative product to natural aggregate. In this study, a comprehensive numerical simulation of foundation beams resting on soils incorporating conventional and sustainable materials has been performed. The foundation beams considered include some with conventional concrete properties and some with sustainable concrete properties. Additionally, the material conditions of soils are assessed, using six different mixed recycled aggregates as filling material. Based on the numerical simulation, the deflection, rotation, bending moment, shear force and spring force capacities of conventional and sustainable foundation beams resting on soils exhibited slightly different behaviour depending on the recycled concrete aggregate and mixed recycled aggregate ratios. Finally, comparing the numerical simulation results of soil-structural interaction members incorporating conventional and sustainable materials indicated that the soil-structure interaction modeling process applied to conventional foundation beams resting on soils is also valid for sustainable members.
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    THE RESILIENT MODULUS OF HYBRID CONSTRUCTION AND DEMOLITION WASTES REINFORCED BY A GEOGRID
    (Univ Maribor, 2022) Sarici, Talha; Ok, Bahadir; Mert, Aykan; Comez, Senol
    The use of construction and demolition wastes (C&D) in engineering applications is an important development for better sustainability. The main objective of this study, therefore, was to increase the use of C&D by improving their engineering behaviour. For this purpose, two methods were employed in this study: first, adding the virgin aggregates (VA) to the C&D, called hybrid C&D (C&D-VA), and second, reinforcing the C&D with a geogrid material. Test samples were prepared in six groups.The first three test groups were prepared with C&D, VA and C&D-VA. The other three test groups were formed with geogrid-reinforced C&D, VA and C&D-VA. Firstly, for the strength characteristics of the samples, the unconfined compressive strength and the California bearing ratio values were obtained with large-scale experiments. Subsequently, for the resilient behaviour of the samples, the resilient modulus values were determined using a large-scale triaxial test device. Consequently, some significant improvements were achieved via the methods employed in this study. In addition, it was observed that the best reinforcement effect for the C&D occurred when the geogrid was used and the VA was added to the C&D.
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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.