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• MakaleAçık Erişim2026Scopus SJRQ3/r/bayburt/11168
  Low-Data Modeling of Shallow Foundations on Cohesive Slopes: A Comparison between Hybrid FEM–RSM and ML Models*

  Kâmiloğlu, Hakan Alper; Gücüyener, Alper

  In geotechnical engineering, accurately predicting the seismic bearing capacity of shallow foundations on cohesive slopes requires proper consideration of nonlinear effects and parameter interactions. However, most studies in the literature address these complex effects inadequately, either with numerical methods that demand a large number of analyses or with machine learning (ML) models that require large and heterogeneous data sets. In this study, it is aimed to propose an approach that allows for a robust analysis of the system and at the same time provides accurate forecasting for situations where working with small and homogeneous data sets is mandatory. Within the scope of the study, seismic bearing capacity analyses were performed using Plaxis 2D for 273 cases where eight independent variables took different values according to the Face Centered Composite Design (FCCD), and a database was created. Multiple Linear (MLR), Multiple Nonlinear (MNLR) Regression Models were established, and ML models, such as Support Vector Regression (SVR), Random Forest (RF), and Extreme Gradient Boosting (XGBoost), were trained. The models were compared with both in-sample and out-of-sample estimation performance, and parametric sensitivity analyses were evaluated by methods such as ANOVA and SHAP. The results show that the MNLR model with natural logarithmic transformation is the most successful method in terms of both accuracy (R² ≈ 0.98) and reflecting parameter interactions, while the SVR algorithm demonstrates the best generalization ability among ML models under low-data conditions. The results also confirm that the ML models effectively capture the parameter effects.

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• MakaleAçık Erişim2025/r/bayburt/16212
  Alkali Aktifleştirilmiş Uçucu Kül ve Polipropilen Elyaf Ile Iyileştirilmiş Yüksek Plastisiteli Siltli Zeminin Durabilite Performansının Incelenmesi

  Kamiloğlu, Hakan Alper; Kurucu, Kutluhan; Durak, Muhammet Oğuz

  Bu çalışmada aktivatör içeriği, fiber takviye türü ve fiber içeriği gibi parametrelerin durabilite özellikleri üzerindeki etkileri araştırılmaktadır. Geleneksel yöntemler durabilite değerlendirmesi için genellikle ıslatma-kurutma veya donma-çözülme döngülerine odaklanırken, bu çalışma saha koşullarını daha doğru bir şekilde simüle eden ıslatma testlerinin önemini vurgulamaktadır. Zemin iyileştirme uygulamalarında, malzemenin kırılganlığı hem geleneksel hem de alkali ile aktive edilen bağlayıcıların kullanımı ile artmaktadır. Lif takviyesi, bu sorunu çözmek ve sünekliği artırmak için yaygın bir uygulamadır. Bu çalışma, çeşitli lif türlerini ve bunların zemin özelliklerinin farklı yönlerini iyileştirmedeki rollerini incelemektedir. Özellikle, farklı tip ve uzunlukları bir araya getiren hibrit liflerin kullanımı, zemin tabakalarının durabilite özelliklerini artırma potansiyeli açısından araştırılmıştır. Çalışmanın deneysel kısmı, lif takviyesi ve alkali ile aktive edilmiş uçucu kül ile stabilize edilmiş yüksek plastisiteli siltli zeminin ıslatma etkilerine karşı davranışını araştırmaktadır. Çalışma, Na2SiO3/NaOH oranının, 3 mm ve 12 mm uzunluğundaki lif içeriğinin ve bu lif uzunluklarının kombinasyonlarının bozulma, serbest basınç dayanımı (UCS) ve ıslatılmış numunelerin dayanım azalması üzerindeki etkilerini ele almaktadır. Numunelerin dayanıklılık performansı çeşitli ıslatma süreleri ile değerlendirilmiştir. Sonuçlar, farklı uzunluklarda karıştırılan hibrit liflerin kullanımının, stabilize edilmiş zeminin durabilite özelliklerini iyileştirmede dikkate değer katkı sunduğu belirlenmiştir.

  İncele
• MakaleAçık Erişim2025/r/bayburt/15944
  Optimization and Mechanical Performance of Alkali-Activated Bottom Ash and Polypropylene Fiber in Deep Mixing Columns

  Yilmaz, Fatih; Kamiloğlu, Hakan Alper; Avlayan, Büşra

  Deep mixing columns (DMC) are one of the widely used soil improvement methods in cohesive and cohesionless soils. Cement and lime are predominantly used as conventional binders in DMC grout. Due to high CO2 emissions from conventional binders, the feasibility of using alkali-activated binders as DMC grout is being investigated. This study was conducted in three main stages. In the first stage, the proportions of bottom ash and activator (mixture of 10M NaOH and Na2SiO3) were optimized to achieve the highest UCS value using response surface methodology (RSM). In the second stage, the influence of polypropylene fiber content was examined in detail by incorporating varying amounts of fibers into the optimized binder-activator mixture to determine the optimal fiber content. Since DMC are fully buried, they are cured in the soil media. In this case, the soil temperature, which varies along the depth of the soil, also becomes the curing temperature of the DCM. Due to climate, soil condition and thermodynamic based parameters, curing temperature of the DMC varies throughout the soil depth. Therefore, in the third stage, the effect of curing temperature on the mechanical properties of the stabilized samples was evaluated under different temperatures. Results of the study revealed optimal UCS values with AAB content of 0.3-0.5 and activator content of 0.45-0.5. Polypropylene fiber reinforcement further improved strength, reaching an optimum at 1.50-1.75% content. Curing temperature played a significant role, with UCS and modulus of elasticity increasing up to 30 °C, indicating the importance of considering environmental factors in DMC design. These findings suggest that the optimized mixture has the potential to replace conventional cement-based binders in DMCs, offering a more sustainable solution with lower carbon emissions. Furthermore, the observed influence of curing temperature highlights the need to account for subsurface thermal variations when designing DMCs, as these factors significantly affect strength gain and long-term performance.

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• MakaleAçık Erişim2024/r/bayburt/16434
  Optimization Of Cantilever Retaining Wall Design Using Improved Teaching-Learning-Based Optimization Algorithms

  Tayfur, Bilal; Kamiloğlu, Hakan Alper

  Retaining structures play a crucial role in geotechnical engineering to support soil levels, prevent slope failure, and create flat surfaces for construction. Designing these structures involves optimizing internal and external stability while minimizing material usage and cost. This study focused on optimizing reinforced concrete cantilever retaining walls using the Teaching-Learning Based Optimization (TLBO) algorithm and an improved version (I-TLBO) with agents. In the context of the study, geometric-structural design variables, geotechnical -structural constraints, and optimization processes were examined. Minimizing weight and minimizing cost of the wall were the objectives considered in the cantilever retaining wall design process. The optimization results were compared with other algorithms in the literature, such as genetic algorithms, evolutionary strategies, and particle swarm optimization. The improved TLBO algorithm demonstrated superior performance, achieved lower design dimensions, and reduced costs. It provided more efficient solutions that pushed design constraints closer to their limits, resulting in a cost-effective and structurally sound cantilever retaining wall design. As a result of the study, the I-TLBO algorithm was found to be more cost and weight-effective than other methods in the optimization of cantilever retaining wall design.

  AtıfOpenAlex2·TR Dizin2

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• MakaleYalnız künye2024Scopus SJRQ2/r/bayburt/12860
  Optimization, Characterization, and Carbon Footprint Analysis of Alkali Activated Waste Tuff and Fly Ash Mixtures for Deep Mixed Columns

  Kamiloğlu, Hakan Alper; Yilmaz, Fatih

  Deep soil mixing (DSM) applications are one of the widely known soil stabilization techniques which can be applied to a wide range of soil types. Cement and lime are the major materials used as binders for DSM applications. However, as conventional binders lead to emit a large amount of CO2 during production, eco-friendly binders suitable for DSM applications have become prominent. Alkali-activated materials are good alternatives to conventional binders. This study was intended to investigate the usability of zeolite rich tuff wastes as an alkali-activated binder in DSM columns. Within this scope, the waste tuff and C-type fly ash mixture were used as an alkali-activated binder, and 10 M NaOH solution was used as an activator. Response surface methodology (RSM) was employed in experimental design to determine optimum components to obtain maximum unconfined compression strength and investigate the interaction between stabilization agents. From the RSM analysis the optimum ratios of activator (X1), waste tuff (X2), and precursor (X3) were determined as; X1 = 0.251, X2 = 0.548, and X3 = 0.538 for maximum UCS. UCS, mineralogical and microstructural characterization (XRF, XRD, SEM, EDX, FTIR) was performed for the DSM samples prepared considering the optimized components. It was determined that the UCS values of the 3, 7, and 28-day cured samples stabilized by considering the optimum values gave UCS values approximately 3 to 5 times higher than the lower limit values recommended by FHWA. As a result of mineralogical and microstructural investigation, the reason for the strength increase in the samples can be attributed to the formation of geopolymeric gel between the soil particles by tuff waste and fly ash activated with alkaline activator. Carbon footprint analyses were performed for 1m3 DSM columns produced with alkali-activated binders and ordinary Portland cement (OPC). From the analyses it was seen that the carbon footprint of the DSM column produced using alkali activated binders is lower than that of the DSM column obtained with OPC. After the general evaluation of the study, it is seen that the hypothesis that waste tuff can be used as environmentally safe alkali-activated binders instead of traditional binders is supported.

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  AtıfScopus6·OpenAlex6

  İncele
• MakaleAçık Erişim2024Scopus SJRQ2/r/bayburt/11597
  Investigating the Effect of Polypropylene Fiber on Mechanical Features of a Geopolymer-Stabilized Silty Soil

  Kamiloğlu, Hakan A.; Kurucu, Kutluhan; Akbaş, Dilek

  This study investigates the stabilization of silty soil using alkali-activated fly ash and fibers with lengths of 3 mm and 12 mm. The study examines the effects of hybrid fiber length, fiber content, fly ash content, and activator content on the mechanical properties of the geopolymerstabilized samples. The objectives of this paper are 1) to examine the effect of activator content and fly ash content on the UCS, Al/Si ratio, and SiO2/Na2O ratio of the stabilized samples using a statistical approach, 2) to investigate the effect of hybrid fiber length on UCS, secant modulus, flexural strength, toughness, and flexural load-deformation characteristics of the stabilized soil. A statistical approach was employed to investigate the relationship between fly ash content, alkali activator content, and UCS value. Optimal fly ash content and alkali activator content were determined based on the statistical model. The geopolymer structure of the stabilized soil was characterized via SEM, EDS, XRD, and FTIR analyses. The effects of fly ash and alkali activator content on UCS, Al/Si ratio, and SiO2/Na2O ratio were determined using the derived statistical model. The study demonstrated that activator content, a critical factor in compaction, significantly influences the UCS value, as much as the effect of the Si/Al and SiO2/Na2O ratios. Additionally, variations in fly ash content led to an increase in the UCS value of up to 15%. Moreover, changing the activator content resulted in a maximum 12-fold increase in UCS value. Incorporating hybrid fibers for stabilization led to higher secant modulus (up to 30%), flexural strength (up to 6%), and ductility without compromising UCS.

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  AtıfScopus20·WoS17·OpenAlex18

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• MakaleAçık Erişim2023Scopus SJRQ1/r/bayburt/14417
  New RSM-FEM-Based Active Lateral Earth Thrust Coefficient Determination Method for Inverted T-Type Cantilever Retaining Walls Supporting Narrow Granular Backfill

  Kamiloglu, Hakan Alper

  This study was aimed to (1) investigate the failure surface mechanism occurring behind the wall supporting narrow backfill with experimental and numerical approaches; (2) determine the effect of internal friction angle (phi), friction (delta), heel length (beta), foundation thickness (alpha), backfill inclination (psi), and backfill width (theta) parameters on lateral earth thrust coefficients; and (3) derive finite-element analysis (FEM)-response surface method (RSM)-based lateral earth thrust coefficient equations for inverted T-type retaining walls supporting narrow backfill. The study was performed for granular backfill. A small-scale test was performed to investigate the failure surface mechanism in the narrow granular backfill. The particle image velocimetry method was employed to determine failure surface patterns for various heel lengths and backfill widths. Finite-element (FE) analyses were also performed to verify the experimental results. From the analyses, it was seen that two characteristic soil blocks formed behind the horizontally translated wall. Due to these soil blocks, the wall was divided into three characteristic regions. Lateral active earth thrust coefficients were derived for the regions. RSM was employed to derive FE-based lateral earth thrust coefficient estimation equations for each region. In this context, three design matrices were created, comprising 76 runs. In the design, parameters phi, delta, beta, alpha, psi, and theta were used as independent variables. A total of 76 FE analyses were performed for various parameter combinations. The results of the FE analyses were used as a response. From the statistical analyses, lateral active earth thrust estimation equations for narrow backfill were derived. The suggested equations were compared with the results of experimental, numerical, and analytical studies, and it was seen that the method gives reliable results. The effects of independent variables and their interactions on lateral earth pressure coefficients were examined.

  AtıfWoS3·OpenAlex3

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• MakaleAçık Erişim2023Scopus SJRQ2/r/bayburt/13127
  Optimizing and investigating durability performance of sandy soils stabilized with alkali activated waste tuff-fly ash mixtures

  Yilmaz, Fatih; Kuvat, Ahmet; Kamiloğlu, Hakan Alper

  The search for alternative environmentally-friendly materials to Portland cement is increasing its importance in geotechnical engineering as in other fields. In this study, alkali activated waste volcanic tuff (BT) and fly ash (FA) utilized as an alternative to conventional binders. The specific objectives of this paper were to, (1) optimize fly ash, waste tuff and activator content using Response Surface Methodology (RSM), (2) investigate the UCS performance of the optimum amount of alkali-activated fly ash and waste tuff mixtures as a binder in soil stabilization by comparing with various codes, (3) characterize the optimized parameters, (4) examine durability performances of the samples. Optimum binder and activator content and effect of waste tuff on strength characteristics were evaluated statistically with RSM approach. XRF, XRD, FTIR analyses were performed to verify the synthesized alkali activated material in the inner structures of the optimized samples. The durability and mechanical properties of samples stabilized with alkali activated binders against soaking condition, wetting-drying and were investigated. Destructive and non-destructive methods were employed to examine mechanical and durability characteristics. Unconfined compression strength, strength reduction ratio, soil deterioration, and water absorption capacity was taken into account to evaluate durability performances. UCS values of the stabilized samples were compared with limit UCS values suggested by several standards. As a result of the study it was determined that alkali activated waste tuff and fly ash mixture shows significant mechanical and durability performance in soil stabilization, and capable to use as an alternative to conventional non-green binders.

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  AtıfScopus6·WoS4·OpenAlex8

  İncele
• MakaleYalnız künye2023Scopus SJRQ1/r/bayburt/13016
  Gamma-ray and neutron shielding capability of blended cement-stabilized barite fillers developed by maximum density method

  Gökçe, H.S.; Öksüzer, N.; Kamiloğlu, H.A.; Yılmaz, F.

  The disposal of radiological wastes in the deep geological repositories has become an important issue for the reduction of hazardous risks on the human and biological environments. In this study, blended cement-stabilized barite fillers against gamma rays and neutrons have been developed with the use of the maximum density method by considering various amounts of water (100–300 kg/m3), binder (4–10%), and compaction energy (500–2000 kJ/m3). According to the experimental series of these filler materials, satisfactory response surface results have been achieved in the study. The experimental results revealed that compacted filling material can ensure an efficient shielding capability for gamma rays and neutrons when designed with a density of 3.064 g/cm3. An increase in binder content, water content, and compaction energy has improved the compressive strength of these materials up to 37 times according to that of the poorest series. Neutron and gamma-ray shielding capabilities were found to be 119 and 14% higher than those of the poorest filler material, respectively when theoretical and experimental results are considered in the study.

  AtıfScopus4·WoS3·OpenAlex5

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• MakaleAçık Erişim2023Scopus SJRQ2/r/bayburt/12900
  The Toughness of Polypropylene Fiber-Reinforced Foam Concrete under Various Uni- and Tri-Axial Compression Loads

  Gökçe, H.S.; Öksüzer, N.; Kamiloğlu, H.A.; Eyüboğlu, M.; Yılmaz, F.

  Foam concrete has recently become a key construction material in terms of meeting the special needs of modern engineering applications such as thermal insulation, absorption of static and dynamic loads. In this study, the effect of polypropylene fiber content and various uni- and tri-axial compression loads on the toughness response of polypropylene fiber-reinforced foam concrete was investigated. Up to a certain strain level (0.1 mm/mm), the ultimate compression stress of specimens under uni- and tri-axial loading increased from about 1 MPa to 16 MPa with the increased target densities of foam concrete. There was a strain-hardening capability of low-density foam concrete while the specimens failed by strain-softening in the high-density series. The optimum fiber amounts were found to be 3.9%, 4.6%, and 6.4% for low, medium, and high target densities of foam concrete, respectively. At low-density series, the bubbles were observed to be relatively bigger and mostly merged with each other. A reduction in foam content (vice versa, increasing target density of mixture) and the presence of fiber resulted in smaller pore size and a more homogenous distribution of them in the matrix. In conclusion, the desired pore structure and efficient bridging of fibers in the matrix allowed the production of favorable foam concrete with higher toughness.

  AtıfScopus14·WoS10·OpenAlex14

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