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Öğe A 3D finite element analysis of the modular block retaining walls with corner turns(Transportation Research Board, 2015) Hamderi, Murat; Güler, ErolThe design manuals for Geosynthetic Reinforced Soil retaining walls include the methodology for various conditions except the case where the wall has curved corner turns. Lately, there has been an increase in the frequency of problems associated with these types of walls. One of the typical problems is cracking/separation of the segmental blocks. The most common method for identifying the cause of problems is a 2D plain-strain analysis which is insufficient for the current case. Therefore in this study, a more robust modeling approach was considered. A 3D finite element (FE) model which is capable of modeling corner turns was created. The main elements of the model are modular blocks, interface layers, soil and geosynthetic reinforcements. As the first step, a base model was defined. The base model included reinforcements with the lowest stiffness. The base model was evaluated in terms of block displacements and stresses. In the other models, reinforcement stiffness and the soil modulus were increased or decreased to evaluate its effect on block displacements and stresses. According to the modeling results, the elastic modulus of the reinforcements and the soil modulus are very effective on block separation and cracking. The separation of blocks could be decreased by increasing the reinforcement stiffness and proper soil compaction. It is considered that the cracking of blocks was related to excessive moments developing in those blocks. The moments are reduced when the reinforcement stiffness was increased. It can be concluded that the cracking of blocks is less likely to happen under reduced moments.Öğe Açısal dönme tabanlı aktif ve pasif toprak itkisi(2023) Hamderi, MuratKonsol istinat duvarlarında oluşan aktif ve pasif itki duvarın dönme ve yer değiştirmesi ile yakından ilgilidir. Klasik zemin mekaniği çerçevesinde yapılan hesaplarda duvarın yeteri kadar döndüğü ve yer değiştirdiği kabul edilerek aktif ve pasif itkilerin kararlı durumdaki değerleri kullanılır. Özellikle pasif itki için kararlı durumdaki değerleri kullanmak hesabın doğruluğunu olumsuz etkilemektedir. Bu çalışma kapsamında aktif ve pasif itkiler için elde edilmiş açısal dönme tabanlı aktif ve pasif itki formülleri tanıtılacaktır. Literatürdeki diğer bazı formüller ve sonlu elemanlar modelinden elde edilen sonuçlar da kullanılarak bir konsol duvar örneği çözülecek, genel bir karşılaştırma yapılacaktır.Öğe An investigation on the formation of cracks at the corner turns of the modular block earth walls(Springer International Publishing Ag, 2019) Hamderi, Murat; Güler, Erol; Raouf, AymanThe design manuals for Geosynthetic Reinforced Soil Retaining Walls include the methodology for various conditions, except the case where the wall has a curved corner turn. Lately, some problems were reportedly associated with these types of walls. One of the typical problems is cracking/separation of the modular blocks. The most common method for analysing the behaviour of reinforced soil walls is a 2-D plane-strain analysis, which is insufficient for the current problem. Therefore, in this study, a 3-D finite-element (FE) model, that is capable of modelling corner turns, has been established. The main elements of the model are modular blocks, interface elements, soil, and reinforcements. As a first step, the performance of the FE model was evaluated by comparing the stress-strain response of a laboratory-scale wall with its counterpart in the FE program. Later, a large-size modular block wall model was created and run with various input parameters. The modelling results revealed that the reinforcement stiffness and the soil modulus are effective in the separation and cracking of blocks. It is considered that the cracking of blocks is related to an excessive stress build-up. These stresses reduced when the reinforcement stiffness increased. It is foreseen that the crack occurrence is less likely to happen under reduced stress.Öğe Comprehensive group pile settlement formula based on 3D finite element analyses(Japanese Geotechnical Soc, 2018) Hamderi, MuratIn the past, formulas for the settlement of group piles considered only a few input parameters and offered only a limited approximation of the actual settlement. Nowadays, however, thanks to the fast-growing performance of personal computers, it is possible to create large 3-dimensional finite element models with a better and more reliable settlement approximation. On the other hand, 3-dimensional finite element methods for piles are not very common in practice since the required procedure is comparatively cumbersome, expensive and needs a bit more expertise. In order to address this issue, a pile settlement formula was developed in the present study based on about 120 finite element model configurations. The group pile settlement formula incorporates the dimensions of a rectangular raft, namely, the diameter, length and spacing of the piles, vertical uniform pressure, soil moduli up to five layers, ultimate pile-soil resistance, pile-tip resistance and elastic modulus of the piles. In addition to this, the average deflection rate of the raft is estimated. The reliability of the finite element model is verified through laboratory-scale group pile tests. The proposed formula is also checked against five well-documented case studies. The formula may help engineers optimize group pile configurations more efficiently by applying the quality of the 3D finite element estimation to practice. (C) 2018 Production and hosting by Elsevier B.V. on behalf of The Japanese Geotechnical Society.Öğe Estimation of horizontal displacements for geosynthetic reinforced soil wall(2023) Güler, Erol; Hamderi, MuratNowadays, the geotechnical design trend is increasingly heading towards the serviceability limit state. However, the current practice in the design of geosynthetic reinforced soil (GRS) walls mostly relies on ultimate limit state. Commonly available design software programs provide typical factor of safety values against various failure modes. With increasing height and variability in GRS walls, the deformation characteristics of the GRS walls also become an important parameter in the design. In this paper, an expression has been developed to predict the horizontal deformation of a GRS wall using a set of data obtained from about sixty-four finite element model configurations. The horizontal deformation expression includes wall height, internal friction angle and elastic modulus of backfill, length, spacing and stiffness of geosynthetic reinforcements. It has been found out that all these parameters contribute to the horizontal displacement of a GRS wall. In addition, some comparisons have been made to reveal the influence of each individual parameter on the horizontal displacement of the wall.Öğe Finite element-based coefficient of lateral earth pressure for cohesionless soil(American Society of Civil Engineers, 2021) Hamderi, MuratIn addition to various factors, the magnitude of lateral earth pressure depends on the direction and amount of the wall rotation. The current literature presents several expressions to calculate lateral earth pressure that captures the soil geometry and load characteristics. However, to the best of the author’s knowledge, there is no practical expression in the literature, in which the amount of wall rotation is incorporated. In this study, using the results of finite element (FE) models, one formula for the coefficient of active and four formulas for passive earth pressure will be presented. In each of the four passive pressure formulas, a different perspective will be adopted. Especially in two of the passive earth pressure formulas, the amount of wall rotation and soil modulus will be included as input parameters. For validation purposes, a physical retaining wall test will be modeled in the FE program and, subsequently, the test and model results will be compared.Öğe Finite element-based p-y curves in sand(Springer, 2023) Hamderi, MuratP-y curves are used in the prediction of non-linear soil resistance resulting from the horizontal pile movement. Many of the p-y curves have been developed in the 1970s for the petroleum industry to predict the horizontal capacity of piles supporting oil platforms. These curves are based on the beam theory fed by strain-gauge data installed on several full-size pile tests. In this particular study, a p-y curve formula for sand was developed using 34 finite element combinations. The p-y curve formula includes the input of soil modulus, soil friction angle, soil unit weight and pile diameter. The results of the formula and the finite element program were validated against the test data available in the literature.Öğe Footing settlement formula based on multi-variable regression analyses(Techno-Press, 2019) Hamderi, MuratThe formulas offered so far on the settlement of raft footings provide only a rough estimate of the actual settlement. One of the best ways to make an accurate estimation is to conduct 3-dimensional finite element analyses. However, the required procedure for these analyses is comparatively cumbersome and expensive and needs a bit more expertise. In order to address this issue, in this study, a raft footing settlement formula was developed based on ninety finite element model configurations. The formula was derived using multi-parameter exponential regression analyses. The settlement formula incorporates the dimensions and the elastic modulus of a rectangular raft, vertical uniform pressure and soil moduli and Poisson's ratios up to 5 layers. In addition to this, an equation was offered for the estimation of average deflection of the raft. The proposed formula was checked against 3 well-documented case studies. The formula that is derived from 3D finite element analyses is useful in optimising the raft properties.Öğe Kazık gruplarında eksenel yük dağılımının bulunması için yeni bir yöntem(2019) Hamderi, MuratLiteratürde grup kazıklarının eksenel yük dağılımını hesaplayan analitik bir yöntem mevcut değildir. İleri derecede hiperstatik olan bu sistemlerin çözümü bazı nümerik yaklaşımlarla yapılabilmektedir. Uygulamada ise genellikle kazık yükleri eşit alınır ya da kazık yükleri üst yapı modeline eşdeğer yaylar yerleştirilerek hesaplanır. Bu hesaplar radye-zemin teması ile aktarılan kuvveti göz önüne almadıklarından kaba bir yaklaşım sağlarlar. Son zamanlarda kazıklı radye sistemler için zeminin de içinde tanımlanabildiği 3-boyutlu numerik çözümler kritik projelerde kullanılmaktadır. Ancak bu yöntemler sıradan projeler için pahalı olmakta ve uzun sürmektedir. Bu pahalı ve uzun süren yaklaşıma alternatif olarak, bu çalışma kapsamında, 3-boyutlu sonlu elemanlar tabanlı bir kazıklı radye temel yük dağılımı formülü tanıtılmış ve formül bir vaka çalışmasına uygulanmıştır. Formül, kazık çapını, boyunu, sıklığını, yanal ve uç direncini; radye kalınlığını, yayılı yükü ve 5 adet zemin tabakasının zemin modülünü bünyesine almaktadır. Ayrıca, bu formül sayesinde radye-zemin teması ile aktarılan yük de hesaplanabilmektedir. Bu sayede kazıklara gelen yüklerin en az yüzde 20 oranında daha az çıkacağı tahmin edilmektedir.Öğe Kazıklı radye temellerin oturma tahmini için yeni bir yöntem(2018) Hamderi, MuratLiteratürde kazıklı radye sistemlerin oturması için verilen ampirik formüller oturmayı sadece kaba bir yaklaşıklıkla tahmin edebilmektedir. Kazıklı radye sistemler için hassas oturma tahmini ancak 3-boyutlu sonlu elemanlar yöntemleri ile mümkün olmaktadır. Öte yandan sonlu elemanlar yöntemleri, formül tabanlı yaklaşımlara göre daha karmaşıktır ve bu yöntemlerin yürütülmesi için görece uzun bir süreye ihtiyaç duyulmaktadır. Bu süreyi kısaltmak amacıyla, bu çalışma kapsamında, 3-boyutlu sonlu elemanlar tabanlı bir kazıklı radye temel oturma formülü tanıtılmış ve formül 2 adet vaka çalışmasına uygulanmıştır. Formül, kazık çapını, boyunu, sıklığını, yanal ve uç direncini; radye kalınlığını, yayılı yükü ve 5 adet zemin tabakasının zemin modülünü bünyesine almaktadır. 3-boyutlu sonlu elemanlar analizi kalitesinde sonuç veren kazıklı radye temel formülünün, kazıklı radye temel sistemlerinin optimize edilmesinde pratik bir çözüm sağlayacağı düşünülmektedir.Öğe Kazıklı radye temellerin oturma tahmini için yeni bir yöntem(2018) Hamderi, MuratLiteratürde kazıklı radye sistemlerin oturması için verilen ampirik formüller oturmayı sadece kaba bir yaklaşıklıkla tahmin edebilmektedir. Kazıklı radye sistemler için hassas oturma tahmini ancak 3-boyutlu sonlu elemanlar yöntemleri ile mümkün olmaktadır. Öte yandan sonlu elemanlar yöntemleri, formül tabanlı yaklaşımlara göre daha karmaşıktır ve bu yöntemlerin yürütülmesi için görece uzun bir süreye ihtiyaç duyulmaktadır. Bu süreyi kısaltmak amacıyla, bu çalışma kapsamında, 3-boyutlu sonlu elemanlar tabanlı bir kazıklı radye temel oturma formülü tanıtılmış ve formül 2 adet vaka çalışmasına uygulanmıştır. Formül, kazık çapını, boyunu, sıklığını, yanal ve uç direncini; radye kalınlığını, yayılı yükü ve 5 adet zemin tabakasının zemin modülünü bünyesine almaktadır. 3-boyutlu sonlu elemanlar analizi kalitesinde sonuç veren kazıklı radye temel formülünün, kazıklı radye temel sistemlerinin optimize edilmesinde pratik bir çözüm sağlayacağı düşünülmektedir.Öğe Kum zeminde p-y eğrileri için yeni bir yöntem(2023) Hamderi, MuratP-y eğrileri yatay kuvvetlere maruz kazıkların zeminin verdiği tepkiyi hesaplamak için kullanılırlar. Birçok p-y eğrisi 1970 yıllarında, petrol şirketlerinin okyanuslar üzerine kurduğu platformları destekleyen kazıkların yanal kapasitelerini hesaplamak için geliştirilmiştir. Bu eğriler kaba veya ince daneli zeminlerde yapılan yanal kazık yükleme deneylerinden elde edilen verilere dayanır. Deneysel verileri barındırması sebebiyle güvenilir ancak çok az sayıda deneye dayandıklarından kaba bir yaklaşıma sahiptirler. Öte yandan günümüzde 3 boyutlu yapı zemin etkileşimini modelleyen yazılımların yaygınlaşması ile yanal kazık kapasitesi ile ilgili bilgisayar ortamında değişik parametreleri içeren sayısız deney yapılabilmektedir. Bu çalışmada, bilgisayar ortamında yapılan kazık yükleme deneyleri sonucunda elde edilen kum zeminler için p-y eğrisi formülü tanıtılacaktır.Öğe New approach to group pile load estimation(Asce-Amer Soc Civil Engineers, 2019) Hamderi, MuratCurrent literature lacks an analytical method for estimating pile load distribution due to the statically indeterminate nature of pile groups. In practice, such estimations are accomplished by finite-element-based analyses or numerical interaction methods, which require computer implementations. A disadvantage of these implementations is that they extend the total duration time and cost of a project. In order to address this issue, a group pile load formula was developed based on 120 finite-element (FE) model configurations. The group pile load formula incorporates the dimensions of a rectangular raft, diameter, length and spacing of piles, vertical uniform pressure, soil moduli up to five layers, ultimate pile-soil and pile-tip resistance, and the elastic modulus of piles. The formula is capable of calculating pile loads at 25 different locations. Additionally, the portion of load carried by the piles as well as through the raft-soil contact can be estimated. Predictions from the FE model and the formula were verified with respect to the observed results from three case studies. The formula developed will help engineers to optimize their group pile configurations efficiently by providing an accurate group pile load estimation.Öğe New displacement method for free embedded cantilever walls in sand(2024) Hamderi, MuratIn the current literature, there is no practical formula to calculate the horizontal displace ment of cantilever walls. To fill this gap, in the present study, eight formulae for the estimation of wall displacement were developed based on 431 FE wall model configurations. Each formula considers factors such as the wall height, embedment depth, surcharge load, unit weight, internal friction angle, elastic modulus of the surrounding soil, and flexural rigidity of the wall. The FE model, which was used in the development of the formula, was also validated against a physical laboratory study. In addition, the outputs obtained from the formulae were compared with the results of two laboratory studies and a real site study. Finally, a parametric study was performed to estimate the influence of formula input parameters on wall displacement.Öğe Numerical analysis of reinforced soil-retaining wall structures with cohesive and granular backfills(ICE Publishing, 2015) Demirkan, M. M.; Güler, Erol; Hamderi, MuratThe failure mechanisms of reinforced soil segmental walls with extensible reinforcements were studied by performing a numerical analysis using the finite element method. The numerical approach was first verified against the results of three instrumented full-scale structures reported in the literature. Finite element models with different combinations of reinforcement spacing, reinforcement length and backfill soil were analysed. The –c reduction method, which is a special shear strength parameter reduction technique, was applied to simulate the failure conditions. The results of –c reduction analysis were used to evaluate assumptions used in current design procedures for geosynthetic-reinforced soil walls. In particular, shear strains were used to identify failure surfaces. Interpretation of the results indicated that, for both granular and cohesive backfills, the potential failure surface gradually shifts to a direct sliding mode as the system approaches failure. As a result, under working loads the potential failure surface used in current design analysis is correct, but the failure plane of a geosynthetic-reinforced soil-retaining wall at failure approaches a direct sliding type or a bilinear plane, which starts from the toe of the wall with a very shallow slope.Öğe Pilot-scale modeling of colloidal silica delivery to liquefiable sands(Elsevier B.V., 2015) Gallagher, Patricia M.; Hamderi, MuratPassive site stabilization is a developing technology for the in situ mitigation of the risk of liquefaction without surface disruption. It involves the injection of stabilizing materials into liquefiable saturated sand. In this study, a pilot-scale facility (243 cm by 366 cm in plan 122 cm deep) was used to inject a dilute colloidal silica stabilizer into liquefiable sand specimens. The grout advancement was monitored in real time using electrical conductivity cells embedded in the specimens. Injection rates ranging from 65 to 9000 ml/min/well were used to investigate the optimal rate of grout delivery. In tests with low injection rates, the delivery performance was low due to sinking, while at higher injection rates, sinking was less noticeable. After the treatment, the degree of grout penetration was evaluated by excavating the model. The in situ unconfined compressive strength was measured using a pocket penetrometer, and soil blocks were excavated for additional unconfined compressive testing. Moreover, the 3-D flood simulator, UTCHEM, was utilized to simulate the experimental results and to predict the injection rates for adequate stabilizer delivery. The results of the strength testing demonstrated that as little as 1% by weight of the colloidal silica provides a significant improvement in strength after a month of curing. The study also revealed the feasibility of delivering colloidal silica to liquefiable sands by implementing a large-scale treatment.Öğe Radye temel oturma hesabı için yeni bir yöntem(2020) Hamderi, MuratLiteratürde radye temellerin oturması için verilen formüller, elastik bir yaklaşım sağlamakta, temel kalınlığının ve farklı zemin tabakalarının hesaba katılmasına olanak tanımamaktadır. Formüllerdeki bu eksiklikler, uygulamacıları proje verilerinin daha detaylı olarak tanımlanabildiği sonlu elemanlar programlarını kullanmaya yöneltmiştir. Ancak sonlu elemanlar programı kullanımı, sıradan projeler için pahalı olmakta ve uzun sürmektedir. Bu pahalı ve uzun süren yaklaşıma alternatif olarak, bu çalışma kapsamında, 3-boyutlu sonlu elemanlar tabanlı bir radye temel oturma formülü tanıtılmış ve formül iki vaka çalışmasına uygulanmıştır. Formül, radyenin elastisite modülünü, enini, boyunu, kalınlığını, yayılı yükü ve 5 adet zemin tabakasının zemin modülünü ve Poisson oranını bünyesine almaktadır. Önerilen bu yöntem ile mühendisler radye temel oturmasını ve sehimini kolay ve güvenilir bir şekilde hesaplayabileceklerdir.
