Person: ÖNALP, AKIN
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ÖNALP
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AKIN
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Publication 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 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 Geotechnical Properties Of Adapazari Silt(Springer Heidelberg, Tiergartenstrasse 17, D-69121 Heidelberg, Germany, 2012-11) AREL, ERSİN; ÖNALP, AKIN; TR2172; TR136055The geotechnical properties of silts have not been investigated extensively, because they are not found in every soil environment. It is even more difficult to understand the behaviour of silts when they are encountered in appreciable volumes. It has recently been claimed that such fine-grained soils have a potential for liquefaction, similar to sands a fact that was confirmed during the 1999 Marmara earthquake in Turkey. This paper provides a basis for explaining the unique behaviour of silts in seismic conditions by investigating their physical and mechanical features. The results are ultimately expected to provide a satisfactory answer to the as yet unexplained issue of how silts behave during earthquakes.Publication Diagnosis of the transition from rock soil in a granodiorite(ASCE-AMER SOC CIVIL ENGINEERS, 1801 ALEXANDER BELL DR, RESTON, VA 20191-4400 USA, 2004-09) AREL, ERSİN; ÖNALP, AKINThis paper describes an attempt to develop a method to define when granodiorite loses its properties as a rock and transforms into soil material. The research program approached the problem from a mechanistic point of view by comparing the pore water pressures generated during isotropic compression with the apparent-and micro-porosities, in terms of a newly proposed pore size distribution index as well as the compressive strengths of the specimens tested. A site was selected for study where weathering of the rock is not accompanied by the production of clay minerals, thus eliminating the complications introduced by the presence of highly compressive zones in the matrix. Samples tested using various criteria indicated that changes in the pore-size distribution can realistically reflect the transformation sought. It appears that further studies should be directed towards determination of the changes in the pore geometry, whereby a scientific definition of the transformation from rock to soil can be made.Publication 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 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 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.Publication Subsurface characterization at ground failure sites in adapazari, Turkey(ASCE-AMER SOC CIVIL ENGINEERS, 1801 ALEXANDER BELL DR, RESTON, VA 20191-4400 USA, 2004-07) Bray, J. D.; Sancio, R. B.; Durgunoğlu, T.; Youd, T. L.; Stewart, J. P.; Seed, R. B.; Çetin, O. K.; Baturay, M. B.; Christensen, C.; Karadayılar, T.; ÖNALP, AKINGround failure in Adapazari, Turkey during the 1999 Kocaeli earthquake was severe. Hundreds of structures settled, slid, tilted. and collapsed due in pail to liquefaction and ground softening. Ground failure was more severe adjacent to and under buildings. The soils that led to severe building damage were generally low plasticity silts. In this paper, the results of a comprehensive investigation of the soils of Adapazari, which included cone penetration test (CPT) profiles followed by borings with standard penetration tests (SPTs) and soil index tests, are presented. The effects Of Subsurface conditions on the Occurrence of ground failure and its resulting effect on building performance are explored through representative case histories. CPT- and SPT-based liquefaction triggering procedures adequately identified soils that liquefied if the clay-size criterion of the Chinese criteria was disregarded. The CPT was able to identify thin seams of loose liquefiable silt. and the SPT (with retrieved samples) allowed for reliable evaluation of the liquefaction Susceptibility of fine-grained soils. A well-documented database of in situ and index testing is now available for incorporating in future CPT- and SPT-based liquefaction triggering correlations.Publication 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 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.