Person: AREL, ERSİN
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AREL
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ERSİN
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Publication Metadata only Taşkent (Özbekistan) Zeminlerinin Geotekniği(2019-11-13) ÖNALP, AKIN; Duran, İlhan Burak; Duru, Ali Can; MERT, AHMET CAN; AREL, ERSİN; 258088; 2172; 136055; 293894Çin’den Bulgaristan’a kadar geniş alanlar lös olarak bilinen topraklarla kaplıdır. Kalınlığı yüzlerce metreye varabilen bu zeminlerin öne çıkan özelliği; suyla karşılaştıklarında gösterdikleri “göçme” davranışıdır. Yüzeysel temellerde ciddi oturma sorunları yaratabilen bu özelliğin değerlendirilmesi lös kuşağında yeralan Özbekistan’ın Taşkent zeminleri için gündeme getirilmiştir. Bu çalışmada kent merkezinde geniş bir adaya yayılacak iş merkezi / rezidans için gerçekleştirilmiş altı farklı zemin inceleme programının sonuçları değerlendirilerek kentte bundan sonra yapılacak yapılaşma çalışmalarına ışık tutulması hedeflenmiştir. Yapılan laboratuvar ve arazi deneyleri Taşkent zemininin lös olarak değerlendirilemeyeceğini göstermektedir.Publication Open Access Analysis of a Prefabricated Vertical Drain (PVD) Soil Improvement Project(Turkish Chamber Civil Engineers, 2022) MERT, AHMET CAN; AREL, ERSİN; ÖNALP, AKINA settlement analysis has been carried out for several sectors of a rail station yard improved with prefabricated vertical drains (PVD) in Istanbul, that exhibited prolonged consolidation beyond the predicted values in certain sectors of the treated zone. Final settlement and End of Primary (EOP) settlement times have been estimated theoretically as well as using the Asaoka graphical procedure. The compliance of settlement-time curves with in-situ measurements and Asaoka solution has been investigated. A geotechnical model was developed for finite element and three-dimensional consolidation analyses. The settlement curves obtained by varying horizontal-vertical permeability coefficient ratio (k(h)/k(v)) and in-situ measurements have been compared, and k(h)/k(v) values corresponding to 90% degree of consolidation has been computed for all sectors. The effect of drain spacing (S-drain) as well as drain length (L-drain) on the rate of consolidation have been evaluated for each sector, keeping the specified ratios constant. The times corresponding to 95% degree of consolidation (t(95)) have been calculated using the theoretical solution and compared to in-situ measurements. Calculated t(95)'s has also been compared to their estimated values by varying the spacing (S-drain) and the length (L-drain). Additionally, the required intervals of S-drain and L-drain have been obtained corresponding to the calculated t(95) times. The analyses suggest that the main reason for prolonged consolidation was the horizontal to vertical permeability coefficient ratio. According to the analysis results, PVD implementation was not efficient in clays having k(h)/k(v) of approximately unity. The main conclusion of this study was to discover the necessity for optimizing the variables in any such project. The efficacy of the works can be significantly enhanced if simultaneous evaluation of the parameters S-drain and L-drain and the permeability ratio k(h)/k(v) is carried out prior to field work. Otherwise, "accidents" may emerge as found out in this project.Publication Metadata only Yayılı Temel BoyutlandırmadaYatak Katsayısı Kavramının Uygulanabilirliği(2018-09) Bozkurt, İbrahim; AREL, ERSİN; ÖNALP, AKIN; 136055; 2172Bildiride, yatak katsayısı kavramının yayılı temel boyutlandırılmasında ne denli uygulanabilir olduğu araştırılarak bu yöntemle yayılı temellerde hesaplanan oturmaların, doğrusal olmayan davranışı esas alan yöntemlerle arasındaki farklar irdelenmektedir. Bu amaçla; aynı sayısal problemlerin, yatak katsayısına dayalı Winkler, geliştirilmiş Vlasov yöntemiyle ve zemin ortamının sadece sürekli sonlu elemanlarla modellendiği doğrusal elastik ve doğrusal olmayan malzeme davranışını içeren analizleri yapılmıştırPublication Metadata only Turba Üzeri̇nden Geçirilen Boru Hatları için Dolguda Rijit Kolonla Zemi̇n İyileştirmesi(2018-09) Koçak, F.Seçkin; AREL, ERSİN; ÖNALP, AKIN; 136055; 2172Zeminde jet grout ile rijit kolon oluşturma; yöntemi, hızı ve görece düşük maliyeti nedeniyle Türkiye'de son yıllarda birçok zemin iyileştirme projesinde uygulanır olmuştur. Bu gelişme kazık uygulamasına bağımlı inşaat mühendisleri için önemli bir aşama sayılabilirse de tercih yapmada kararları dikkatle almak gerektiği açıktır. Bu tür uygulamalardan biri, evvelki yıl içinde bir göl kenarından geçirilecek boru hattı projesinde gündeme gelmiştir. Yaklaşık 200m uzunlukta bir kesimden çapları 1.20m ve 0.50m olan borular, ortalama 2m kalınlıkta bir dolgu yapılarak buradan geçirilmek istendiğinde, yapılan sondajlar gölün bu kesiminde 8m kalınlıkta bir turba tabakası bulunduğunu göstermiştir. Yapılan hesaplamalar dolgunun 20 yıl içinde 110cm düzeyinde oturacağını gösterdiğinden zemin iyileştirmesi yapılması gündeme gelmiştir. İşveren maliyetleri düşürme ve imalatı hızlandırma amacı ile iyileştirmenin rijit kolonlarla yapılmasını istemiştir. Bu bildiride, Temmuz 2016- Mayıs 2018 arasında dolgunun davranışı, hesaplanan-ölçülen oturma eğrilerinin karşılaştırılması anlatılmaktadır. İlk bulgulara göre, hesaplanan oturma eğrisinin, iyileştirilmiş ve iyileştirilmemiş kesimlerde ölçülmüş oturma eğrisinden daha yüksek değerler gösterdiği görülmüştür. Öte yandan, jetgrout uygulaması yapılmış kesimlerde ölçülen oturmaların işlem görmemiş kesimdekilerden daha yüksek çıkması da ilginç bir bulgu olarak kayda geçmiştir. Kolon oluşmaması, ortamdaki organik asitlerin özelliğine yorumlanmıştır.Publication Restricted Field Simulation of Settlement Analysis for Shallow Foundation Using Cone Penetration Data(Elsevier Science Ltd., 2021) MERT, AHMET CAN; AREL, ERSİNThis paper deals with the settlement analysis of a vertically loaded strip footing by the use of two-dimensional random field finite element method. Total settlement and rotation of the footing have been calculated by elasto-plastic solution in finite element model. Deformation modulus of soil E-d was assigned conforming to 2D Gaussian random field using Karhunen-Loeve series expansion. Spatial variability of E-d was represented by the horizontal and vertical correlation lengths (theta(vE) and theta(hE)). CPTu database from Adapazari, Turkey has been employed to estimate the correlation lengths. Soil profile was modelled with 4 layers in accordance with random field from in-situ test results, and correlation lengths were assigned to each different layer. Random field realizations were produced by MATLAB code, and probability density functions (PDF) of maximum total settlement and rotation of the footing were constructed using Monte Carlo Simulations by iterative solutions of each realization with finite element analysis. Probabilities of failure (P-f) by settlement and rotation were calculated from PDFs. Initially, the analysis was carried out using average values of each horizontal and vertical correlation lengths that were assigned to every soil layer. Subsequently, analyses were iterated with maximum and minimum values of the correlation lengths in order that both the effect of horizontal and vertical spatial variability can be considered. 1000 calculations were performed for the 5 analysis models, with 200 random field realizations for each model. The effect of varying theta(vE) and theta(hE) on total settlement and rotation of the footing has also been investigated.Publication Embargo The effect of clay mineral content on the dynamic response of reconstituted fine grained soil(Springer, Van Godewijckstraat 30, 3311 Gz Dordrecht, Netherlands, 2018-10) Olgun, Güney C.; AREL, ERSİN; ÖNALP, AKIN; 136055; 2172Fine grained soils with considerable amount of silt may exhibit sand-like or clay-like behavior depending on several factors such as the amount of fines and clay content, as well as the consistency limits, other variables being kept unchanged. This unpredictable behavior makes silts highly problematic, especially under seismic conditions. This paper describes the laboratory behavior of low plasticity Adapazari silt, known to be highly sensitive to cyclic loading. In the first phase of the basic study reported herein, Adapazari silt was mixed with different percentages of bentonite and kaolin and the behavior of these reconstituted mixtures was investigated in cyclic triaxial and dynamic simple shear tests. The purpose was to identify basic index properties and their threshold values to delineate sand- and clay-like behavior. Such a distinction may make it possible to complement field penetration resistance with appropriate adjustment factors to evaluate the pore pressure development potential, thus the risk of ground failure during an earthquake. The results show that there is a range of liquid limit and plasticity index values above which cyclic failure is significantly mitigated. It can now be stated that silts of intermediate and high plasticity may be deemed of relatively low potential for ground failure during seismic loading.Publication Metadata only Adapazarı Zeminlerinde Sıvılaşabilirliğin Lojistik Regresyon ile Değerlendirilmesi(2018-09) MERT, AHMET CAN; AREL, ERSİN; ÖNALP, AKIN; 258088; 136055; 2172Adapazarı bölgesinde, geniş veri tabanına sahip koni penetrasyon deney (PCPT) sonuçları kullanılarak zemin sıvılaşıma olasılığının belirlenmesi amacıyla bir lojistik regresyon modeli geliştirilmiştir. Model girdileri olarak, temiz kum eşdeğeri normalize koni uç direnci (q ciN,cs) ve 7.5 moment büyüklüğü için düzeltilmiş çevrimsel gerilme oranı (CSRm=7.s) kullanılmıştır. Lojistik regresyon, iki değişkenli sonuç çıktısına sahip olayların gerçekleşme olasılıklarının belirlenmesinde kullanılan bir doğrusal regresyon modelidir. Sıvılaşmanın olası iki sonucunun aranması ('sıvılaşma var' veya 'sıvılaşma yok') lojistik regresyon modeline uygundur. CPT lokasyonlarının koordinatları ve koni uç direnci verileri, 0-6m derinlik aralığı için elde edilen ortalama sıvılaşma olasılıkları ile birlikte noktalanarak şehrin üç boyutlu sıvılaşma olasılık yüzeyi oluşturulmuştur. Sıvılaşma potansiyelinde derinliğin etkisinin ifade edilmesi amacıyla üç boyutlu yüzey 0-2m, 2-4m ve 4-6m derinlik aralıklarına bölünerek tekrar oluşturulmuştur. Her bir derinlik aralığı için sıvılaşma olasılıkları, 1999 Adapazarı depreminde belirlenmiş olan sıvılaşan ve sıvılaşmayan bölgeler bilgileri ile karşılaştırıImıştır. Elde edilen sıvılaşma olasılıklarının yüzeye yakın derinliklerde en yüksek olduğu ve artan derinlikle azaldığı belirlenmiştir. Sıvılaşma olasılıkları; 0-2m için en yüksek, 4-6m arasında ise en düşük bulunmuştur. Bu durum sıvılaşmanın yüzeye yakın birkaç metre içerisinde etkili olduğunu göstermektedir. Önerilen model ile uyum, modifiye olabilirlik oranı indisinin p2=0.95 bulunması ile oldukça başarılı olmuştur.Publication Metadata only Rock slope stability assessment of limestone quarry; an example from Istanbul Cebeci region, Turkey(Springer International Publishing Ag, Gewerbestrasse 11, Cham, Ch-6330, Switzerland, 2015) Yılmaz, Murat; Tuğrul, Atiye; Er, Selman; Ertin, Altay; Tokgöz, Nuray; AREL, ERSİN; 111644; 8623; 176451; 136055The Cebeci Region is characterised by famous outcrops of Carboniferous Limestone which is mined out for aggregate production. The aim of this study is to investigate slope stability problems for heavily jointed karstic limestones in an aggregate quarry. Limestone quarries have turned into steep cliffs of bare rocks which threaten the safety of construction and have also negative influence on the aesthetics in the Cebeci Region. For this study, firstly, field studies were carried out involving detailed discontinuity surveys. Then, laboratory tests were conducted to determine physical, mechanical and elastic properties of the intact rock and shear strength parameters of the discontinuities for each different lithology. Kinematical analyses were performed to determine the potential kinematic failures and stability sites of the quarry. Also, finite element method analyses was carried out for the global stability of cut slopes with applying a number of different disturbance zones, parallel to the slope faces. According to the results of kinematic and numerical analysis, different types of failures are expected in different sites of quarry. Based on the field studies and stability analyses of the cut slopes, slope geometry optimization and necessary support measures such as wire mesh and rockfall barriers are suggested.Publication Metadata only The Spatial Distribution of Liquefaction Susceptibility by Logistic Regression Model Adapted for Adapazari, Turkey(2020) MERT, AHMET CAN; AREL, ERSİN; ÖNALP, AKIN; 258088; 136055; 2172A logistic regression model has been developed for evaluation of soil liquefaction by the use of cone penetration test (CPTu, PCPT) on data collected from Adapazari, Turkey. The model inputs are the clean sand equivalent normalized cone tip resistance (q(c1N,cs)) and cyclic stress ratio corrected for moment magnitude of 7.5 earthquake (CSRM=7.5) that was experienced in 1999. Liquefaction probabilities (P-L) are obtained for each district of the city for which CPTu data is available with the proposed logistic regression model. Average liquefaction probabilities of the depth interval 0-6 m and coordinates (Longitude, Latitude) of CPT soundings were plotted to construct a liquefaction probability map by longitude and latitude. In order to show the effect of depth in liquefaction potential, the obtained liquefaction probability contours were reconstructed by dividing 0-6m depth into three narrow sublayers of 0-2m, 2-4m and 4-6m wherein liquefaction was observed during the earthquake. For each depth interval, liquefaction probabilities of the districts are compared with the observed liquefied and non-liquefied sites in the city after 1999 Adapazari Earthquake.Publication Metadata only Liquefaction Of Silts: The Adapazari Criteria(Springer, Van Godewijckstraat 30, 3311 Gz Dordrecht, Netherlands, 2010-08) Bol, Ertan; Sert, Sedat; Özocak, Aşkın; AREL, ERSİN; ÖNALP, AKIN; TR53055; TR2172; TR136055; TR19215; TR136056Ground failures in the form of liquefaction, loss of bearing capacity and soil softening have been observed during the 1999 Marmara (Turkey) earthquake. Research to understand the failure phenomena has been carried out since the earthquakes. This paper attempts to provide explanations to the liquefaction failure of silts in seismic conditions. Findings from a large amount of data collected in the city of Adapazari on the physical and mechanical properties of soils is presented. A geomorphological map of the city has shown that there are surprising horizontal and vertical variations of the facies due to the activity of rivers in the past. Cases of liquefaction appear to have concentrated in former backswamp areas where silts and sandy silts were deposited by crevasse splays. Properties of the soils in zones of liquefaction and non-liquefaction have been determined down to a reasonable depth by measuring the average size, clay content and liquidity index as well as cone penetration resistances with porewater pressures to discover that there is significant discrepancy among those profiles susceptible to liquefaction and non-liquefying deposits. A set of "Adapazari Criteria" is proposed which is intended to improve over the "Chinese Criteria" and is simple enough to be universally applicable. This classification is similar to the existing criteria but emphasizes more on the clay content in addition to measuring the liquid limit and the liquidity index as well as the average size.