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Öğe 3D Numerical Response of a Single Pile Under Uplift Loading Embedded in Sand(Springer, 2019) Emirler, Buse; Tolun, Mustafa; Yildiz, AbdulazimIn this study, the uplift behavior of a single pile has been investigated in sand, numerically. The pile used in the analyses is in circular shape in 25 mm diameter. The investigated parameters are embedment ratio of pile (L/D = 8, 12, and 16), material of pile (steel, aluminum, and delrin) and relative density of sand (RD = 30%, 50%, and 80%). For this purpose, a series of finite element analyses have been carried out by using Plaxis 3D. The results of analyses have been compared with the theoretical methods proposed for a single pile embedded in the loose sand. According to the results of both methods, the uplift capacity in the loose sand obtained from theoretical method gives a good agreement with that of present numerical analysis, and all investigated parameters affect significantly the uplift behavior of the pile. Moreover, the uplift capacity increases with the increase of the embedment ratio (L/D) and relative density of sand (RD). Additionally, the capacity of steel pile is more than aluminum and delrin piles.Öğe An experimental study of rough single pile and pile group under uplift loading in sand(Taylor & Francis Ltd, 2021) Emirler, Buse; Tolun, Mustafa; Yildiz, AbdulazimFoundation systems of specific structures such as high-voltage power lines, communication towers, long factory chimneys, sea platforms, columns carrying the advertising boards and signs in freeways and railways are subjected to different loads. These structures are also under the influence of uplift load and the foundation systems should be designed according to the factors affecting the uplift capacity. In this study, the uplift capacity of a rough single pile and pile group embedded in sand is investigated, experimentally. The uplift capacities of a single pile and pile group configuration of 2 x 2 under the effect of various parameters such as pile embedment ratio (L/D), spacing ratio between the piles (S/D) and relative density of sand (D-r) are examined by using a rough steel pile in 25 mm diameter with circular geometry. Furthermore, it is aimed that the uplift capacity of each pile is determined by being connected a load cell to each pile in the group. The value of (S/D)(opt) is determined to be affected by the relative density of sand, and the interaction between piles eliminates in larger S/D in dense soil. It is observed that the uplift capacity increases considerably with the increase of all investigated parameters.Öğe Contribution of using geogrid under a shallow foundation on sand subjected to static and repeated loads: Laboratory testing and numerical simulations(Techno-Press, 2021) Tolun, Mustafa; Epsileli, Sefer E.; Emirler, Buse; Yildiz, Abdulazim; Tutumluer, ErolThis paper focuses on the use of a certain punched and drawn geogrid to increase the bearing capacity of a circular shallow foundation subjected to a combination of static and repeated loads. In the experiments, the foundation is first subjected to a prespecified static load, afterwards, a repeated load derived in different proportions of the applied static load is superimposed to that static load. The variables investigated in the tests are the number of geogrid layers, the amplitude of repeated load, and the number of load cycles. The effect of these variables is also investigated by a finite element numerical modeling approach verified with one-dimensional site response analysis, and as a consequence of this effort that refers to the innovation of the study, the consistency between the results obtained from both methods is observed. The test results show that the displacements of the shallow foundation increase rapidly in the first 100 load cycles in all cases. After that, the rate of increase is reduced until about 2000 load cycles and the displacements become negligible. From the experiments, 2 geogrid layers were found to be quite effective in reducing displacements due to both static and dynamic loading cases. In other respects, finite element simulations of the physical experiment have produced numerical results in good agreement with the test results. Plus, the main contribution of the numerical simulation is to indicate the deformed mesh outputs of the model including the geogrids for the foregoing variables.Öğe Dynamic Response of a Single Pile Embedded in Sand Including the Effect of Resonance(Budapest Univ Technology Economics, 2020) Tolun, Mustafa; Emirler, Buse; Yildiz, Abdulazim; Gullu, HamzaIn this paper, responses of a single pile embedded in sand soil (loose and dense) under dynamic loading (sinusoidal dynamic vibrations of 0.1 g to 0.5 g) have been investigated by two-dimensional analysis using the finite element method (FEM). Viscous (dashpot) boundaries have been used for taking the boundary effects of far-field into account. The applicability and accuracy of site responses of two-dimensional analysis due to the FEM modelling have been well verified with one-dimensional site responses. The results indicate that the relative density of sand (loose, dense) becomes prominent for the displacements of the pile, specifically under the frequency effects of resonance. While the pile in loose sand causes the displacements of 0.1 m to 0.5 m, the pile in dense sand leads to the displacements of 0.05 m to 0.25 m, proportionally with the dynamic loads from 0.1 g to 0.5 g. Moreover, the displacements reach their peak value at the frequency ratio of the resonance case. Viscous boundaries are found sufficient for modelling excessive displacements due to dynamic loading. However, the displacements reveal that high vibrations (> 0.1 g for loose sand, > 0.2 g for dense sand) influencing the pile deformations are critical for the issues of settlements. This is more significant for the resonance case in order for ensuring sufficient design. Consequently, the findings from the study are promising good contributions for pile design under the dynamic effect.Öğe Effect of dilatancy on tension response of completely rough piles embedded in granular soils(Pergamon-Elsevier Science Ltd, 2024) Tolun, Mustafa; Emirler, Buse; Ertugrul, Ozgur L.; Yildiz, AbdulazimPile surface roughness is an important characteristic determining the displacement response of piles under various loading conditions since it leads to surface friction resistance. Considering that no capacity contribution is acquired from the pile tip, the effect of surface friction becomes more pronounced for tension piles. Pile surfaces can be classified as smooth, rough, or completely rough according to the normalized surface roughness value (Rn) of piles, and this paper focuses only on the uplift capacity of piles with normalized surface roughness values greater than 0.1 (i.e., completely rough) by employing the PLAXIS3D code verified against results of twelve physical modelling tests reported in the literature. The reason of selecting piles with completely rough surfaces in this study is that dilatancy behaviour can be only observed in the uplift load-displacement relationships of such piles, unlike the piles with smooth or rough surfaces. While numerical simulations are repeated for different normalized surface roughness values (Rn = 0.2, 0.5, 1.0, and 2.0) and different relative densities of sandy backfill (Dr = 25%, 50%, and 75%), the effect of the pile surface friction resistance on the uplift capacity, which occurs as a result of the interaction between the pile surface and sandy soil grains, is studied with special emphasis on soil dilatancy. It is observed that the numerical results are quite compatible with the physical test results. In addition, increasing the pile surface roughness and relative density of sandy soil causes an increase in the uplift capacity, and those capacity increments can only be modelled properly by increasing the dilatancy angle of sandy soil in finite element analyses.Öğe Effect of surface roughness characteristics on the uplift capacity of piles: A physical modelling study(Taylor & Francis Inc, 2023) Tolun, Mustafa; Emirler, Buse; Ertugrul, Ozgur L.; Yildiz, AbdulazimPile surface roughness is one of the significant variables affecting the load-bearing capacity of piles. Especially for piles subjected to uplift loads, this parameter can be considered as the main factor that affects the uplift capacity since there is no contribution originating from the pile tip. According to limited previous research, a pile surface can be evaluated as smooth if pile surface roughness parameter (R-n) is less than 0.02, whereas the pile surface is considered completely rough when R-n value is greater than 0.10. This paper, therefore, is aimed to investigate the validity and effectiveness of the numerical limits previously suggested for R-n and intends to determine the relationship between R-n and soil-pile friction angle. For this purpose, laboratory model tests were performed on 12 small-scale pile models embedded in cohesionless soils having varying densities (D-r=25%, 50%, and 75%). Pile surfaces were specially textured to produce different surface roughness values from 0 to 2. Test results indicated that increasing the relative density of cohesionless soil and the pile surface roughness had a considerable contribution to the uplift capacity and soil-pile friction angle. Furthermore, some typical values of R-n like 0, 0.04, and 0.10 were found to be critical for pile uplift behaviour and capacity, and R-n value should be accepted as zero to consider the pile surface as completely smooth.Öğe 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, AhmetThe 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.Öğe Field test of circular footings on reinforced granular fill layer overlying a clay bed(2012) Laman, Mustafa; Yildiz, Abdulazim; Ornek, Murat; Demir, AhmetThe 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.Öğe Geotechnical properties of recycled construction and demolition materials for filling applications(Elsevier, 2020) Ok, Bahadir; Sarici, Talha; Talaslioglu, Tugrul; Yildiz, AbdulazimModern 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.Öğe Investigation of the construction and demolition materials reinforced by geosynthetics(Emerald Group Publishing Ltd, 2023) Ok, Bahadir; Sarici, Talha; Demir, Ahmet; Talaslioglu, Tugrul; Yildiz, AbdulazimMany 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.Öğe Investigation on determining uplift capacity and failure mechanism of the pile groups in sand(Pergamon-Elsevier Science Ltd, 2020) Emirler, Buse; Tolun, Mustafa; Yildiz, AbdulazimFoundations of some structures such as transmission towers, mooring systems for ocean surface or submerged platforms, tall chimneys, jetty structures are subjected to uplift loading. In such cases, to increase the uplift resistance of piles, pile foundations like anchored piles, batter piles and micro piles are extensively employed depending on in-situ conditions. This paper deals with the contribution of pile surface to the uplift capacity and the failure mechanism obtained for the pile groups in sand, and the main goal of the study is to investigate the effect of the pile surface roughness on the uplift capacity for different spacing ratios between piles. Therefore, the paper presents some findings of a single pile and pile groups embedded in sand under uplift loading. The variables investigated include the pile surface, pile embedment ratio and the spacing ratio between piles. Experiments were conducted to study foregoing parameters, and three-dimensional analyses were performed using the finite element method to illustrate the failure mechanism of pile groups and the interaction between piles for different spacing ratios between piles. The results show that the finite element simulation results indicate good agreement with the experiment results, and all variables significantly affect the uplift capacity of piles.Öğe 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, AbdulazimThe 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.Öğe Stability analyses of a slope reinforced with piles subjected to static and dynamic loading conditions(TUBITAK, 2021) Tolun, Mustafa; Un, Buse; Emirler, Buse; Yildiz, AbdulazimThis paper focuses on a stability analysis related to a highway constructed on a slope with high shear potential reinforced with the piles. For this purpose, a series of two-dimensional simulations were carried out by employing the finite element method. In the study, in order to provide the current state of topography, a numerical model was created based on data obtained from field and laboratory tests. It is aimed to define the safety factor of a slope under both static and dynamic loads, and that value was calculated for the following three cases: (i) for the slope unreinforced with the piles subjected to static loading, (ii) for the slope reinforced with the piles subjected to static loading, (iii) for the slope reinforced with the piles subjected to both static and dynamic loading. The numerical results indicate that it is a good approach to be used the piles to enhance the stability of the slope even though dynamic loading brings about to decline in the slope safety factor. Plus, the relevant value was determined to be 1.446 in the second case explained above while the same value was calculated to be 1.104 in the third case. Therefore, it is understood that the dynamic loads caused by the vehicles should be considered in the design of these kinds of problems, and the improvement method should be evaluated in detail. © 2021, TUBITAK. All rights reserved.
