itüdergisi (E-Journals - İstanbul Teknik Üniversitesi, Istanbul Teknik Uniersity., İTÜ)
itüdergisi (E-Journals - İstanbul Teknik Üniversitesi, Istanbul Teknik Uniersity., İTÜ)Not a member yet
1059 research outputs found
Sort by
Geoteknik bakış açısı ile özgün bir deprem hasar görebilirlik yönteminin geliştirilmesi
Full text linkEarthquake damage assessment methodologies are applied mainly for two purposes; as a damage assessment methodology in urban areas and as a land use study in undeveloped areas for the purpose of city planning. Satisfactory earthquake damage assessment methodologies should incorporate the information from geological and geophysical investigations, quantitative, qualitative analyses and expert interpretations. In today's state-of-the-art, despite the existence of numerous applications in this context, there is still a need for comprehensive and quantitative methodologies to ensure that all the damage-causing phenomena are well understood and included. Regarding these studies, data collection and quality are of primary importance because once spatial database is implemented; it is rarely scrutinized for its correctness, completeness or accuracy leaving behind serious data quality issues. In Turkey devastating earthquakes, which hit Kocaeli and Düzce area in 1999 have created an increasing awareness about the damaging potential of earthquakes. In the context of earthquake preparedness efforts, microzonation projects have been prepared for various districts in Istanbul and Marmara region. In this paper, an integrated earthquake damage assessment methodology is presented to fulfill the need for standardized and quantitative approaches in this area. The approach inherently carries a soil-structure interaction concept by combining the site specific geotechnical and structural properties in a quantitative manner. The basic merit of the proposed methodology is to include all the damage making phenomenon systematically and to evaluate their effects both individually and in combination. Earthquake damage assessment analyses with respect to primary and collateral effects were conducted. The primary damage-causing effect was accepted to be ground shaking and the collateral effects were accepted as liquefaction, seismic bearing capacity degradation and landslides. At the present state of the art, existing spatial earthquake damage assessment studies acknowledge the collateral effects due to liquefaction and landslides but fail to consider those due to seismic bearing capacity degradation of shallow foundations. This consideration is important, because while liquefaction is a threat for loose and granular soils, seismic bearing capacity degradation may occur in almost all types of foundation soils. In this paper, a damage grade was assigned for each individual event and also an integrated damage grade for their combined effects. Assigned damage grades were based on an interpretation of a probabilistic "damage-damage causing event" relationship available in the literature and applicable for the region. The damage grades given in this paper reflect a rough probabilistic evaluation but their function is to define a single decision made over a set of probabilities. The proposed methodology was also applied to Bakirkoy district in Istanbul and the results indicate the effectiveness of the approach. In order to collect the necessary geological, geotechnical data for the spatial analysis 87 borings amounting to 2011 meters were made in an area of 6.1 km2. The study was conducted by a multidisciplinary team of Istanbul University (Istanbul University Report, 2000). An extensive laboratory-testing program was conducted to determine physical and mechanical properties of soil and rock samples recovered from the boreholes. Seismic wave refraction surveys were conducted at 125 locations and electrical resistivity measurements were made at 210 points All the data related to the location of boring logs. geophysical measurement points, three dimensional topography and geology of the region were displayed via GIS maps. The analyses have shown that the district carries a considerable risk of being significantly affected by future earthquakes and therefore damage and consequent economic losses from a great magnitude earthquake centered near the district would be severe. Although it has been applied in Turkey, the proposed methodology has the basic feature of being applicable to any earthquake-prone area. The methodology developed can be extended to add the effects of any other damage making phenomena that may affect the considered region. Keywords: Earthquake damage assessment, ground shaking, liquefaction, seismic bearing capacity degradation.Gerek kentleşmiş, gerekse kentleşmeye açılacak olan bölgelerde olası bir depremin sebep olacağı zararın en aza indirilebilmesi için deprem tehdidinin boyutlarının mevcut yerel ve yapısal koşullarla birlikte oldukça gerçekçi bir seviyede tanımlanması ve alınması gereken önlemlerin buna göre belirlenmesi gerekmektedir. Deprem gibi afetlere karşı hazırlıklı olma, can ve mal kaybını en aza indirme gayretleri insani boyutları sebebiyle küresel niteliktedir. Bu makalede bu kapsamda yapılmış olan detaylı ve özgün bir çalışma tanıtılmaktadır. Şehirleşmiş alanlarda hasar görülebilirlik seviyesinin tanımlanmasına yönelik olarak ve/veya yerleşime yeni açılacak alanlar ile ilgili çalışmalara yön göstermek üzere bir deprem hasar görebilirlik yöntemi geliştirilmiştir. Birincil hasar etkeni olarak yer sarsıntısı, ikincil etkenler olarak sıvılaşma, dinamik yükler altında taşıma gücü kaybı ve heyelan tetiklenmesi göz önüne alınmıştır. Tüm bu etkenler için performans bazlı değerlendirme yapılmıştır. Dinamik yükler altında taşıma gücü kaybına bağlı oluşabilecek oturmalar literatürde ilk kez bu çalışma kapsamında hasar görebilirlik çalışmalarına dâhil edilmiştir. Her bir hasar verici etkenin yaratacağı hasar seviyesi önemsiz hasar seviyesi-çok yüksek hasar seviyesi aralığında puanlamıştır. Bu puanların oluşturulmasında literatürde yer alan önemli veritabanları ve yayınlar kullanılmıştır. Her bir hasar puanı için elde edilen puanlar uygun bir şekilde birleştirilmiş ve böylece her bir nokta için tek bir hasar puanı elde edilmiştir. Makalenin son kısmında geliştirilmiş olan yöntem Bakırköy İlçesi için uygulanmıştır. İlçe için yapılmış olan detaylı arazi çalışmalarına dayanan analizler neticesinde farklı tipteki yapılar için yer sarsıntısı sıvılaşma, taşıma gücü ve sıvılaşmaya bağlı hasar potansiyeli ve toplam hasar görebilirlik incelenmiştir. İlçede tasarım depremi için oluşması beklenen bu hasar seviyeleri CBS ortamında haritalanmıştır. Anahtar Kelimeler: Deprem hasar görebilirlik çalışmaları, yer sarsıntısı, sıvılaşma, taşıma gücü kaybı, heyelan, toplam hasar görebilirlik
Zeminlerin yanal şişme basıncının belirlenmesi
Full text linkExpansive soils can be defined as soils that under some conditions are capable of increasing its volume when inundated. It is well known that structures placed over or in expansive soils face problems due to soil heave upon the change of the soil moisture.The primary aspect of research on swelling has always been to predict the swelling behavior of the expansive soils in the vertical direction. Nevertheless, expansive soils change their volumes in lateral direction as well as in the vertical direction. By restraining the lateral volume change tendency of soils with the construction of a retaining wall or a tunnel lining, the restraining element is being employed with responding the large swell pressures. This additional lateral pressure caused by swelling is being missed in most of the cases during the lateral earth pressure calculations. To predict lateral swelling pressure in a sensitive way has forced the establishment of triaxial swelling pressure tests. Adequate and correct prediction of lateral swelling pressure is important in that the lateral restrainment elements like a retaining wall or tunnel facing can be designed to withstand the earth pressures to act on them in the reality. One of the well known methods for measuring the lateral swelling pressure is the use of a thin wall oedometer which was first introduced by Komormik & Zeitlen, (1965) and then also developed by several investigators. The objective of this study was to investigate the rate of lateral swelling pressures expected to act on retaining systems of deep excavations and tunnels in expansive soils. The variation of swelling pressures dependent on depth and the rigidity of the facing element were investigated. The Lateral Swell Pressure Ring has been redesigned for this study. The ring height has been increased and a pressure cell has been added to the device. Different than the similar device of Ofer (1981), the cell pressure restraining the specimen in lateral direction was hydraulic pressure rather than air pressure. The pressure cell, surrounding the thin walled ring gave the ability to predict the lateral swelling pressures under zero lateral strain conditions. Moreover, three strain gauges have been mounted on the ring, each configured as a quarter bridge, to monitor the non-homogenous behavior of the specimen in the horizontal plane. Several swelling tests have been performed on compacted samples that have been prepared in the laboratory, under similar conditions and using the same clayey soil. The subject of this study was to present a method on the determination of lateral swelling pressure, and the variation of the swelling pressure due to the variation of the initial moisture content is not a matter of subject in this study. For this reason, the initial water content of the samples has been kept constant in the tests. Various test types have been utilized in order to obtain comprehensive lateral swelling pressures. The results are compared with swell pressures obtained in these tests in vertical direction as well as with the triaxial swelling pressure test results of previous studies. First, a series of tests have been made in accordance with the methodology of the previous studies using the thin walled lateral swelling pressure ring. So, by comparing the results obtained from these tests with the results of the tests of other researchers, the reliability of the test set up has been validated. Then, the contribution of the pressure cell, added to the recently designed testing device has been investigated. Swelling pressure tests under cell pressure have resulted with slight higher swelling pressures as expected. The test results have also revealed that a strain induced automatic cell pressure triggering is necessary for greater accuracy for lateral swelling pressure prediction under zero lateral strain conditions. For the case that automatic cell pressure triggering is not present, as in this study, the adjustment of a testing technique like "The Method of Equilibrium (Fourie, 1989)", will avoid side effects of possible failures due to strain based pressure relief. Keywords: Lateral Swelling Pressure, thin walled oedometer.Şişen zeminler, ıslandıkları zaman hacimlerini arttıran zeminler olarak tanımlanırlar. Şişen zemin tabakaları üzerine veya içerisine inşa edilen yapılarda, zemin tabakalarının su muhtevasındaki değişime bağlı olarak gelişen şişme davranışı etkisinde büyük problemler ile karşılaşıldığı bilinmektedir. Şişme basıncına yönelik araştırmalarda genel olarak düşey yönde etkiyen şişme basıncı araştırılmıştır. Oysaki şişen zeminler, hacimlerini düşey ve yatay yönde şişerek genişletirler. Yanal şişme basıncının belirlenmesinin kaçınılmaz hale gelmesi, üç eksenli şişme basıncı deneylerinin gelişimini beraberinde getirmiştir. Bu çalışmanın çıkış noktası, şişme basıncının zemin içerisinde derinlikle değişimi ve zemini destekleyen yapısal kaplama rijitliği ile değişiminin araştırılması olmuştur. Bu amaçla, daha önce yapılan bazı araştırmalarda kullanılan ince cidarlı ödometre üzerinde modifikasyonlar yapılmış, bu çalışma için, şişme basıncı ölçen, inceltilmiş ödometre halkasına sahip düzenek yeniden üretilmiştir. Ödometre halkasının etrafına eklenen basınç hücresi sayesinde, numunenin yanal şişmesi engellenerek, sabit hacimde şişme basıncı deneyleri yapılabilmiştir. Buna ilave olarak, inceltilmiş çelik halkaya yerleştirilen üç adet deformasyon ölçer (strain gauge) çeyrek köprü devresi ile bağlanmış ve her biri bağımsız bir indikatör olarak görev yapabilir hale getirilmiş ve numunenin yatay eksendeki anizotropik şişme davranışı incelenebilmiştir. Anahtar Kelimeler: Yanal şişme basıncı, ince cidarlı ödometre halkası
Geoteknik mühendisliğinde yapay sinir ağı uygulamaları ve bir örnek: Zemin profilinin tahmin edilmesi
Full text link The use of artificial neural networks (ANN) in geotechnical engineering has gained wide application in Turkey as well as the world during the past ten years. A comprehensive literature survey has shown that applications are concentrated in basic areas such as classification, site characterization, liquefaction, hydraulic conductivity, compaction, consolidation as well as practice comprising the problems of retaining structures, settlement of foundations, pile capacity and modeling of soil behavior where the relationship among the several parameters involved is not always thoroughly understood. Several case histories are presented as examples. Latest research shows that artificial neural networks are heading towards unison with fuzzy logic and genetic algorithms and it is certainly superior to the statistical methods.The second part of the paper gives an account of research conducted into estimation of the soil profiles in the city of Adapazari, Turkey. There has been widespread damage and destruction in the city during the Mw=7.4 earthquake in 1999. The damage has largely been blamed on inferior alluvial deposits and parts of the city have been moved to the North where the soil was found to be "sound". The sediments in the city are the products of the meandering river Sakarya which also flooded the region almost biannually. The two processes have resulted in the formation of complex soil profiles and near chaotic profiles are frequent. The silty layers are possibly the source of ground failures, occasionally leading to liquefaction in the absence of sands. A comprehensive soil investigation has been carried out since 1990 by boreholes and cone penetration soundings. The authors have used the rich database available established from previous and current laboratory and field investigations. Out of this voluminous data those pertaining to depths of 2 to 7m have been used for the ANN work, as those depths have been diagnosed as the possible liquefaction zone. Data from 117 CPT sites whose coordinates were known were employed for this study. The 3236 readings of tip resistance and sleeve friction were used to establish the ANN model. The well established Robertson classification chart defines nine types of soil. It requires the normalised values of tip resistance(Qt) and and sleeve friction(Fr) a identify the soil layer. The Qt* and Fr* are further defined to form the spatial distribution by the use of equations. The training matrix even for a limited depth of 5m using the data from 90 CPTU tests came out to be of size 3236x3236, which was difficult to handle. Consequently, thirteen 1800 by 1800 matrices were established (1.60-1.98m, 2.00-2.38m, 2.40-2.78m, 2.80-3.18m, 3.20-3.58m, 3.60-3.98m, 4.00-4.38m, 4.40-4.78m, 4.80-5.18m, 5.20-5.58m, 6.00-6.38m, 6.40-6.78m, 6.80-6.98m). Data from 27 CPTU were used to form the thirteen 540 by 1800 simulation matrices and 1800 by 1800 training matrices. Analyses were carried out on the Matlab 2010a Toolbox7 NNtraintool interface. 60% of the data were employed for Training, 15% for Validation and 15% for Testing. Inspecting the results, it was found that the success rate in estimating the soil profile anywhere in the 26 km2 city area was as high as 92%. This is a surprisingly high success rate considering the highly complex and laterally variable soil profiles throughout the city. Keywords: Geotechnical engineering, artificial neural network, artificial intelligence, soil profile, cone penetration test, site characterization.Dünyada ve Türkiye’de yapay sinir ağlarının (YSA) geoteknik mühendisliğinin pek çok alanında kullanımı son yıllarda yaygınlaşmıştır. Literatür araştırmasında; geoteknik probleminin çözümünde kullanılan YSA nın özellikle; zeminlerin sınıflandırılması, arazi karakterizasyonu, sıvılaşma, geçirimlilik ve hidrolik iletkenlik, sıkıştırma, dayanma yapıları, temellerin oturması, kazık hizmet yükünün tahmini ve zemin davranışının modellenmesi gibi karmaşık ve ilişkinin iyi anlaşılamadığı pek çok doğrusal olmayan problemlerin çözümünde başarılı ve hızlı çözümler sağladığı görülmektedir. Yapılan son çalışmalar, YSA’nın bulanık mantık ve genetik algoritma ile bütünleştiğini göstermektedir. Bu makalenin konusunu, geoteknik mühendisliğinin çeşitli dallarındaki problemlerin çözümünde YSA uygulamalarının genel bir değerlendirmesi oluşturmaktadır. Bu kapsamda YSA modellenmesi ve bu konuda yapılmış yurtdışından ve ülkemizden bazı çalışmalara örnekler verilmiştir. Makalenin ikinci bölümünde yazarlarca geliştirilen Adapazarı zeminlerinde 2-7m arası zemin profilinin CPT verileriyle analizinde yapay sinir ağının kullanımına yer verilmiştir. Koordinatları bilinen toplam 117 adet Koni Penetrasyon (CPT), verilerinden oluşturulan veri tabanı ile her 2cm. de bir alınan toplam 3236 okumayla geliştirilmiş yapay sinir ağı modeli ile rastgele seçilen lokasyonlar için yapılan tahminlerde %92 gibi oldukça yüksek bir başarı elde edilerek arazi karakterizasyonu hakkında yorum yapılabileceği görülmüştür. Anahtar Kelimeler: Geoteknik mühendisliği, yapay sinir ağları, yapay zeka, zemin profili, koni penetrasyon deneyi, arazi karakterizasyonu. 
Çift tabakalı filtreler: Türkiye şartlarına uygun bir tasarım ve değerlendirme
Full text linkSilica sand is the most widely used rapid filter medium around the world. The use of dual-media filtration, however, is now widespread in developed countries. Generally anthracite coal and silica sand are used together in dual-media filters. On the other hand, large water treatment plants in Turkey (including all the older and the new plants constructed by İSKİ and DSİ) still employ single-medium sand filters. A sand/anthracite dual media filter design was evaluated as a possible upgrade of the widely used rapid sand filters in Turkey. Pilot scale direct filtration experiments were carried out using raw and synthetic waters. The raw surface water was obtained from the raw water intake at the İkitelli drinking water treatment plant of Istanbul. Two identical filters were operated in parallel in all the experiments. One filter contained the silica sand medium that is currently used by several large municipalities in Turkey, whereas the other filter contained a layer of the same sand plus an anthracite layer that replaced the topmost 40 cm of the mono-medium sand filter. The properties of the dual media filter were selected such that the currently used sand filters in Turkey can be converted to dual media filters with a minimal amount of effort. Experiments were repeated several times as follows: (i) without the use of a coagulant, (ii-iv) with 3 mg/L, 5 mg/L and 10 mg/L of alum, and (v-vi) with 5 mg/L and 10 mg/L of ferric chloride. Turbidity, particle counts, and head losses were measured and compared as functions of time. In all the experiments carried out in this work, the following were observed: (1) Whenever a coagulant was used, the filter containing sand/anthracite dual media produced effluent turbidities and particle counts similar to those obtained with the sand filter. (2) Sand/anthracite medium generated a smaller clean-bed head loss and smaller clogging head losses than those of the sand filter. Considering the experience with dual media filters over many years in other parts of the world, these findings are not surprising. These findings are significant, however, because they demonstrate the applicability of dual media filtration under unique local conditions. The following factors are important in this respect: (1) The sand medium employed in the dual media filter was the same as the currently used sand in local plants. The same sand can be continued to be used after conversion to dual media filtration. All that is necessary is to replace about 40 percent of the sand by anthracite. Furthermore, the currently used media-retaining nozzles and the underdrain system will not have to be changed. (2) The tests are unique in that, the performance of the particular combination of media sizes and depths used in this study –to the best knowledge of the authors- have not been documented in the literature. (3) Many of the studies comparing dual media filters with mono-medium filters were carried out long time ago and without particle counters, using turbidity as the sole indicator of particle removal efficiency. The use of on-line particle counters in this study allowed a better comparison of the effluent qualities achievable in single and dual media filters. It is concluded that the particular sand-anthracite dual media design selected in this study can be employed to decrease and delay filter head loss development. The use of the dual media filter design described here will allow longer filter runs while obtaining essentially the same effluent quality. Another benefit of converting to dual media filtration will be the more widespread use of direct filtration which is currently not preferred by local engineers even when faced with low turbidity raw waters. Keywords: Drinking water treatment rapid filtration, filter material, silica sand, anthracite coal, particle removal.Silika kumu, bütün dünyada en yaygın olarak kullanılan filtre malzemesi olmakla birlikte gelişmiş ülkelerde çift ve daha çok tabakalı filtrelerin kullanımı yaygınlaşmıştır. Çift malzemeli filtrelerde genellikle antrasit kömürü ve silika kumu birlikte kullanılmaktadır. Ancak Türkiye’deki mevcut büyük arıtma tesislerinde sadece silika kumu kullanımı devam ettirilmektedir. Bu çalışmada, İstanbul’un içme suyunun büyük bir bölümünü sağlayan İkitelli içme suyu arıtma tesisi girişinden temin edilen hamsu ve sentetik olarak hazırlanan sular üzerinde pilot ölçekli hızlı filtrasyon deneyleri yürütülmüştür. Çalışmalarda iki paralel filtre kullanılmıştır. Filtrelerden biri Türkiye’de yaygın olarak kullanılan silika kumunu, diğeri ise antrasit kömürü ve silika kumunu içerecek şekilde çift tabakalı olarak hazırlanmıştır. Deneyler bu iki paralel filtrenin eş zamanlı çalıştırılması ile yürütülmüş ve filtrelerin performansı zamana bağlı olarak bulanıklık, parçacık sayımı ile yük kayıpları ölçülerek mukayese edilmiştir. Çalışmanın temel hedefi değişik filtre malzemesi kombinasyonu kullanımının su kalitesi ve yük kayıplarına olan etkilerini tespit etmektir. Bu çalışmada elde edilen temel neticeler şu şekilde özetlenebilir: (i) Uygun dozajda bir yumaklaştırıcı kullanıldığı takdirde, çift tabakalı (antrasit ve kum) filtrede tek tabakalı (silika kumu) filtredekine eşdeğer çıkış suyu kalitesi elde edilmiştir. (ii) Çift tabakalı filtrede hem temiz yatak (filtrasyon başlangıcındaki) yük kayıpları hem de filtrenin tıkanmasından dolayı ortaya çıkan yük kaybı artışları tek malzemeli kum filtreninkine nazaran mühim ölçüde daha az olmuştur. Anahtar Kelimeler: İçme suyu arıtımı, hızlı filtrasyon, filtre malzemesi, silika kumu, antrasit kömürü, parçacık giderimi
Donatılı kil zemin üzerine oturan yüzeysel şerit temellerin taşıma kapasitesi
Full text linkMany researchers investigated the behavior of surface foundations constructed on reinforced sand (Omar et al. 1993; Khing et al. 1993; Yetimoglu et al. 1994; Das ve Omar 1994; Adams & Collin 1997). However most of the problematic foundation soils are of cohesive nature. Therefore in this study the effect of reinforcing cohesive foundation soils was investigated. Normally the cohesive soil excavated would be replaced by a granular fill. This means that improvement will be obtained due to the geosynthetic reinforcement but also because of the soil exchange. In order to see the effect of geosynthetic reinforcement alone, in this study the backfill was considered to have the same properties as the natural cohesive soil. The foundation behavior is assessed using limit equilibrium and finite element method (FEM). In this study the finite element code, Plaxis was used. A parametric study was conducted. Safety factors were calculated by using the "Phi-c reduction" method in the finite element analyses. In the "Phi-c reduction" approach the shear strength parameters tan and c of the soil are successively reduced until failure occurs. The soil was modeled as Mohr-Coulomb model and the reinforcement as a linear elastic material. In the analyses, no specific interaction model between soil and reinforcement was used. The analyses presented in this study involve strip foundations on clay soil. The problem was analyzed under plane strain condition. The material properties were chosen in accordance with those in the literature to represent a clay soil. The soil parameters adopted were: = 15 kN/m3; E = 25000 kPa (500 * c); = 0.30; = 0o; = 0oand c = 100, 75, 50, 37.5, 25, 12.5 kN/m2. Footing thickness was chosen as 0.143 m and was placed directly on the surface without any embedment. Geosynthetic axial stiffness per unit width was selected as J=2000kN/m to represent a typical geogrid (Deb et. al. 2007). For the finite element analyses, vertical boundary was chosen to have only horizontal fixity and bottom boundary has both horizontal and vertical fixity. The size of the finite element mesh used was the same for all the analyses. It was chosen to be large enough to reduce the boundary effects to a negligible level. Factor of Safety (GS) for bearing capacities of unreinforced soil were calculated first by Limit Equilibrium analysis and then by FEM. The footing width (B=2.5, 5, 10 and 20 m), cohesion of the foundation soil (c=50 and 100 kPa), and surcharge load on footing (100 and 200 kPa) were varied to assess their influence on the safety factor of the shallow foundation. A good agreement was achieved between bearing capacity calculated using limit equilibrium approaches and finite element solutions. The finite element analysis gave factor of safety values directly proportional to cohesion of the clay soil as expected. In order to investigate the influence of the reinforcement on the factor of safety, a parametric study was conducted using different reinforcement configurations. Number of reinforcement layers, depth of the first reinforcement, vertical spacing of reinforcement layers, width of reinforcements and cohesion values of soil were chosen as variables in the analyses. Results obtained are summarized below: As the number of reinforcement layer increases (from one to six), the safety factor increases as well. Regardless of total number of reinforcement layers, the foundation width did not have a significant effect on the bearing capacity. The depth of the first reinforcement varied between 0.05B and 0.7B. The most efficient initial reinforcement depth was found as 0.4B. The vertical spacing between horizontal reinforcement layers (H) were taken as 0.025B, 0.05B and 0.1B. When six reinforcement layers were used, increase in the factor of safety values were calculated as: 7.5%, 12% and 17% for H/B values of 0.025, 0.05 and 0.1 respectively. The reinforcement lengths analyzed were L=B; L=2B; L=3B; L=4B and L=5B. The increase in bearing capacity after a length of L=3B was negligible. BCR and effective reinforcement depth were not affected when cohesion of the soil changed. Keywords: Strip footing, bearing capacity, Finite Element method, clay soil.Geosentetikler zeminin taşıma gücünü arttırmakta donatı olarak kullanılmaktadır. Bu çalışmada kohezyonlu zeminlerde geosentetik donatıların etkilerini daha iyi anlayabilmek için donatılı kil zemine oturan yüzeysel şerit temellerin taşıma kapasiteleri analiz edilmiştir. Hesaplamalarda sonlu elemanlar kodu Plaxis kullanılmıştır. Temel zemini Mohr Coulomb ve donatı lineer elastik malzeme olarak modellenmiştir. Analizlerde Phi-c azaltma metoduyla güvenlik sayıları bulunarak taşıma kapasiteleri hesaplanmıştır. İlk olarak donatısız kil zeminde temel genişliği, sürşarj yükü ve zemin kohezyonunun etkileri incelenmiştir. Nihai taşıma kapasiteleri hesaplanarak literatürdeki limit analiz sonuçlarıyla karşılaştırılmıştır. Daha sonra, donatının etkisini araştırmak amacıyla parametrik bir çalışma yapılmıştır. Donatı sayısı, etkin ilk donatı derinliği, donatılar arası düşey mesafe, donatı genişliği ve zemin kohezyonu parametre olarak seçilmiştir. Analizler sonucunda donatı sayısı arttıkça taşıma kapasitesinin 6 donatı için %17’ye kadar arttığı, etkin ilk donatı derinliğinin 0.4B (B=Temel genişliği) olduğu görülmüştür. Kohezyonlu zeminde donatının çalışmasının zemin kohezyonundan etkilendiği, donatı sayısı 6 iken taşıma kapasitesini kohezyon cinsinden 0.9c kadar arttırdığı görülmüştür. Donatılar arası düşey mesafe arttıkça taşıma kapasitesindeki değişimi gösteren eğrinin eğiminin dikleştiği ve taşıma kapasitesinin büyüdüğü görülmüştür. Donatı genişliğinin temel genişliğinin 3 katından büyük olduğu durumlarda taşıma kapasitesi sabit kalmıştır. Taşıma kapasitesi oranları (BCR) ve etkin donatı derinliği zemin kohezyonundan bağımsız çıkmıştır. Anahtar Kelimeler: Şerit temel, taşıma kapasitesi, Sonlu Elemanlar metodu, kil zemin
Zemin mekaniğinin temelleri
Full text linkResearch on shear strength of soils always had, and perhaps still has, an important part in the development of soil mechanics. Some of the work carried out on the shear strength of cohesive soils is discussed here. Karl Terzaghi came to Istanbul Technical University in 1916 and stayed in Istanbul till 1922. During his stay in Istanbul, he had the opportunity to re-evaluate and reconsider his engineering experiences of the past from the perspective of present. He later wrote, “I was sitting in a mood of depression at an old rustic coffee house overlooking Golden Horn. I suddenly visualised what was needed to obtain a rational approach to the problem involved in earthwork and foundation engineering.” He carried out a series of experiments and made observations. He recognized that the addition of an increment of external pressure to a clay sample resulted in a temporary increment of water pressure of equal magnitude and soil’s intergrain contacts would feel no increment of force until the pore pressure began to dissipate. He defined “the pressure acting in the solid phase of the clay” which is now known as “the effective stress”. At the time Karl Terzaghi stated one of the fundamental principles of soil mechanics (Terzaghi, 1936) “… All measurable effects of a change of the shearing resistance are exclusively due to the changes in the effective stresses….” The principle of effective stress is extremely important concept in soil mechanics. A number of corollaries can be deduced from that principle. The engineering behaviour of soils with similar structure and mineralogy will be the same if they have the same effective stress. If the soil loaded or unloaded without change of volume and without any distortion there will be no change of effective stress. By raising or lowering pore water pressure it is possible to change the volume of the soil. Coulomb studied the stability of earth masses by considering the frictional resistance of a sliding block and published his famous paper in 1776. After Coulomb and many attempts have been made to redefine c and f to improve the equation in view of the new findings. Besides field observations and physical simulation by means of tests and monitoring our understanding of soil behaviour is improved. The Mohr theory of strength has been very useful in predicting stress conditions at failure from triaxial and other shear test results. The theory is based on the assumption that the shear stress on a failure plane is a unique function of the normal stress acting on that plane without particular reference to the associated strains. M. Juul Hvorslev carried out a series of tests on remoulded consolidated clay samples in the soils laboratory of Terzaghi in Wien Technische Hochschule. Hvorslev was aware that a cohesive soil undergoes either decrease or increase in the void ratio depending on its state of consolidation and also this change in the void ratio is simultaneous with the increase or decrease of pore water pressure. The classical work of Peynircioğlu (1939) on the shear strength of remoulded saturated cohesive soils is the earliest verification of Hvorslev’s findings. Roscoe, Schofield, Wroth (1958) in their prominent work define shear strength in three dimensional form by taking deviator stress (q), mean principal effective stress (p) and void ratio (v) as axes. They showed that failure points of clay samples which were initially isotropically consolidated and then loaded in drained and undrained triaxial compression tests fall on the same line in that space. They coined that line as the Critical State Line. The projection of the critical state line onto the q – p plane may be described by q = M p where M is its gradient. Remoulded, reconsolidated samples, such as used by Hvorslev, Peynircioğlu, and stress in their tests may fall into the class of normally and lightly overconsolidated soils. The exact boundaries of the failure surface defined by them are continuously improved and discussed by the introduction of new experimental evidence. Yet the work carried out in the late thirties constituted a major progress still to be challenged. We owe the development of Soil Mechanics and Foundation Engineering in Turkey to Professor A. Peynircioğlu (1908 – 1982). He worked in Istanbul Technical University where he was appointed as full professor in 1943. His lectures was always well prepared and inspiring. As an experienced engineer he was always consulted for constructions with difficult ground conditions. He established Soil Mechanics Research Institute of Istanbul Technical University, and Geotechnical Laboratory, lead and chaired the group constituted Turkish National Committee of Soil Mechanics and Foundation Engineering. Keywords: Soil mechanics, geotechnical engineering, Istanbul Teknik Üniversitesi, Robert College.İstanbul, Zemin Mekaniği’nin bilimsel bir disiplin olarak kurulduğu yerdir. Hikaye, Karl Terzaghi’nin İstanbul Teknik Üniversitesi’nde, o zamanki adı ile Yüksek Mühendis Mektebi’nde 1916 yılında görev alması ile başlamaktadır. Terzaghi’nin 1918’e kadar Yüksek Mühendis Mektebi’nde, daha sonra 1922’ye kadar Robert College’de çalıştığı yıllarda, yapmış olduğu deneyler, geliştirmiş olduğu kavramlar inşaat mühendisliğinde yeni ufuklar açmıştır. Ortaya attığı “efektif gerilme” kavramı, zemin davranışı ile ilgili o zamana kadar karanlıkta kalan bir çok konunun anlaşılmasını sağladığı gibi yeni araştırmaları teşvik etmiş, yeni bulgulara yol açmıştır. Türkiye’de zemin mekaniğinin inşaat mühendisliğinin bir dalı olarak yerleşmesi ve gelişmesi, daha sonraki yıllarda, Ahmet Hamdi Peynircioğlu’nun çalışmaları ve uzak görüşlülüğü sayesinde gerçekleşmiştir. A. H. Peynircioğlu, Türkiye’de ilk kez, “zemin mekaniği ve temel inşaatı” bilim dalını ve kürsüsünü kurdu, birçok öğrenci yetiştirdi. Şimdi kendi adını taşıyan İTÜ Zemin Mekaniği Laboratuvarı’nı kurdu. İnşaat mühendisi olarak çeşitli zemin koşullarında zarif, ders niteliğinde çözümler meydana getirdi. Yurdumuzda yapılan çalışmaların duyurulması ve uluslararası toplantılara sunulması amacıyla 1947 yılında “İTÜ Zemin Mekaniği Araştırma Kurumu”nu kurdu, gelişen üniversiteler ortamını da dikkate alarak, 1974’te “Zemin Mekaniği ve Temel Mühendisliği Türk Milli Komitesi”nin kurulmasını sağladı. Bugün, üniversitelerde ve araştırma kurumlarındada görev alan, projelerde sorumluluk yüklenen birçok geoteknik mühendisi, Ahmet Hamdi Peynircioğlu’nun araştırıcı, öğretim üyesi ve insan olarak verdiği örneği hatırlamaktadır. Anahtar Kelimeler: Zemin mekanği, geoteknik mühendisliği, İstanbul Teknik Üniversitesi, Robert College
Alüminyum yüzey işleme endüstrisi proses atıksularından elektrokoagülasyon yöntemiyle florür giderimi
Full text linkFluoride concentration higher than 4 mg/L creates several dental problems and decompositions in the skeletal structure. Daily intake of 6 mg fluoride may cause articulation diseases, weight losses and bone breakages. Therefore, fluoride concentration in drinking water has been strictly regulated as a maximum value of 1.5 mg/L by Turkish Standards Institute (TSE), World Health Organization (WHO) and European Commission (EC). Owing to its high toxicity, legal authorities have established the discharges standards for fluoride from wastewater treatment plants. Therefore, the increasing demand for the control of fluoride being released from industrial activities has led to the search of more effective treatment methods for fluoride bearing effluents. Although, several physico-chemical treatment methods such as adsorption using different types of adsorbents such as activated alumina, activated carbon, fly ash etc., coagulation with alum, chemical precipitation with lime, and electrocoagulation using aluminum electrodes have been addressed for removal of fluoride from the samples bearing moderately low amount of fluoride in the related literature. Among these treatment processes, electrocoagulation (EC) is deemed a promising one in removing fluoride from industrial effluents. The target of the present study is to examine the treatability of an aluminum surface treatment effluent bearing high amount of fluoride by EC with aluminum electrodes and to explore the effect of varying operating parameters such as the applied current density, initial pH, and electrolyte (NaCl) concentration on fluoride abatement as well as organic matter removal and aluminum reduction. In order to assess the effects of the operation parameters on process performance and to determine the optimum operation conditions in terms of removal efficiencies, a detailed experimental study was performed using composite samples taken from an aluminum surface treatment process. An aluminum surface treatment effluent bearing high amount of fluoride (3180-6490 mg/L) and aluminum (2695-4690 mg/L) together with organic matter (485-750 mg/L) was used in the experimental study. NaCl was selected as an electrolyte because of high efficiency on EC. The electrocoagulator consisted of a 10 L-capacity polyethylene reactor equipped with 4 pairs of anodes and cathodes made of aluminum. The process performence was followed by COD, fluoride, and aluminum. In order to determine the effect of the applied current density on EC process performance a wide range of the applied current density varying between 3.7 and 18.6 mA/cm2 was applied at an electrolyte concentration of 500 mg NaCl/L and at original pH of sample (2.52). The results indicated that increasing the applied current density improved fluoride removal efficiencies. Nevertheless, this improvement in fluoride removal was observed after 30 minutes of operation time. In these experiments commenced at an initial pH of 2.52, solution pH gradually increased and reached to ~6.0. The lowest remaining aluminum concentration was obtained at the end of EC process performed at the highest applied current density. The results obtained at EC applications run at an initial pH of 2.54, a high NaCl concentration of 1500 mg/L, and at a wide range of applied current density varying between 3.7 and 29.8 mA/cm2 indicated that increasing the applied current density increased fluoride and aluminum abatement efficiencies and shortened the reaction time. Similar to EC runs conducted at 500 mg NaCl/L solution pHs gradually increased up to 6.0 during these EC applications. Up to 40% COD removal efficiencies were obtained at the end of these EC applications. The effect of electrolyte concentration and initial pH on process performance was investigated at an applied current density of 18.6 mA/cm2 for an NaCl concentrations of 1500 and 3000 mg/L and at initial pHs of 2.52 and 3.8. EC performed at initial pH of 3.8 yielded better fluoride abatements and aluminum reductions than EC run at original pH of 2.52.While an increase in electrolyte (NaCl) concentration from 1500 to 3000 mg/L slightly enhanced removal efficiencies at the beginning of EC operation, almost the same fluoride abatements as well as COD and aluminum reductions were obtained at the end of 180 minute EC operation. In the present study, the electrocoagulation using aluminum electrodes proved to be a promising treatment method for fluoride removal as well as aluminum and organic matter reductions from an aluminum surface treatment effluent bearing high amount of fluoride and aluminum. Keywords: Aluminum, aluminum surface process, aluminum electrode, electrocoagulation, fluoride.Bu çalışmada, yüksek florür içeriğine sahip atıksuları temsil etmek üzere, alüminyum yüzey işleme endüstrisinden alınan numuneler üzerinde, elektrokoagülasyon (E.K.) prosesi ile florür ve diğer kirleticilerin giderimi ile ilgili deneysel çalışmalar yürütülmüştür. Alüminyum yüzey işleme endüstrisi proseslerinden alüminyum yüzey temizleme ve durulama banyosundan alınan atıksu numuneleri hacimsel olarak 1:1 oranında homojen bir şekilde karıştırılarak kompozit numuneler hazırlanmıştır. Alüminyum yüzey temizleme banyosunda sırasıyla %19, %8.5 oranında hidroflorik asit ve fosforik asit ile birlikte tensit (noniyonik) kullanımından dolayı, pH’sı düşük, florür, alüminyum ve KOİ konsantrasyonu yüksek atıksular meydana gelmektedir. Bu atıksuların arıtımı gerek florür gerekse alüminyum ve KOİ değerlerinin alıcı ortam deşarj standartlarını sağlayabilmesi açısından önem kazanmaktadır. Deneysel çalışmalarda E.K. uygulamalarında işletme parametrelerinin proses performansı üzerine etkileri incelenmiştir. İşletme parametreleri olarak, akım yoğunluğu, elektrolit olarak kullanılan NaCl konsantrasyonu ve pH ele alınmıştır. Ham kompozit numuneler üzerinde uygulanan E.K. denemelerinde artan akım yoğunluğu ve zamana bağlı olarak florür için yaklaşık %97 giderim verimi elde edildiği, artan akım yoğunluğu ve NaCl konsantrasyonuna bağlı olarak alüminyum gideriminde yüksek giderim verimlerine ulaşılabildiği ancak organik maddeyi temsil eden KOİ gideriminin ise %40 civarında kaldığı tespit edilmiştir. Deneysel çalışmaların sonucu olarak ham numunelerin E.K. prosesi ile gideriminde florür, alüminyum ve KOİ parametreleri için alıcı ortam deşarj standartlarının sağlanamadığı tespit edilmiştir. Anahtar Kelimeler: Alüminyum, alüminyum yüzey işleme, alüminyum elektrod, elektrokoagülasyon florür
Karma bir balast suyu arıtım sistemi ve elektrokimyasal teknoloji
Full text linkThe transportation of exotic species in ballast tanks is one of the most important environmental problems of the ship industry at the global levels. The technologies that will be adapted to both existing and new built ships should be developed immediately to minimize problems caused by the ballast water and sediment. There are a number of techniques taken into consideration to eliminate the organisms in ballast water. However, it is generally agreed that a single treatment method would not be sufficient to prevent the translocation these organisms. Consequently various projects which focus on the hybrid systems were initiated. These systems generally include one primary treatment and one or more secondary treatment techniques. Primary treatment is achieved by mechanical treatment such as filters. Secondary treatment may consist several physical and chemical options. Chlorine disinfection is one of the most applied techniques. The main subjects of concern about employing chlorine disinfection for ballast water organisms is the safety risk during handling and onboard storage of chlorine gas or HOCl solutions. On the other hand, electrochemically generation of disinfectants, especially oxidants as HOCl, is an emerging technique. Electrochemical generation of active chlorine on board would eliminate those unfavorable features of chlorine disinfection. This work has been prepared from the doctoral thesis which is titled as "Electrochemical Cell Application for Ballast Water Treatment" and submitted to Institute of Science and Technology of Istanbul Technical University. This study has been conducted within the project "BaWaPla - Sustainable Ballast Water Management Plant", funded by the European Union under contract number 031529, which is started at 15/11/2006 and finalized at 15/05/2010. A new hybrid ballast water treatment system has been developed within the project. This self-controlled system consists of filter systems, UV and electrochemical technologies. The electrochemical component of BaWaPla produces active substances onboard through electrolysis of seawater and eliminates the require-ment to carry or store hazardous and corrosive chemicals. A laboratory system has been prepared by Project partner LVPG GmbH, Germany and provided to Istanbul Technical University. This system is used for test assumptions and proposals for the best and optimal cell design. Employing electrolysis techniques to produce disinfectants, saline water/seawater is introduced into an electrochemical cell in the heart of the test system. Electrochemical reaction within the cell results in the production of highly effective "Hypochlorous acid rich" disinfectant. Disinfectant fluid can be affected by the design of the fluid path within the electrochemical cell, the selection of material used to produce the permeable membrane that separates the fluid paths or to direct solution past the anode and cathode (electrodes) as well as the electrical current applied to the electrodes. The choice of materials used for coating the relevant electrodes must also be considered. In this study five different electrochemical cells are assessed for BaWaPla system. The cells are supplied from FumaTech GmbH, Germany. The cells are referred as "standard cell, FTEC 100, FTEC 500, EC 100 Nr. 201, EC 100Nr. 240". The changing parameters of the cell designs are the geometry of electrodes, the dimensions of electrodes and the materials used for electrodes and their coatings. The results show that, the enlargement of electrode surface results in more chlorine figures in di-sinfectant. On the other hand, suitable electrode and coating material are essential for "reverse polarity" operation to avoid scaling of Ca2+ and Mg2+ on electrodes and clogging the membrane. Taken into consideration of these results of laboratory works, FumaTech GmbH produced new cells for BaWaPla. These cells have the electrode dimensions as FTEC 500 and the material used for electrodes and their coatings is the same as EC 100 Nr. 201. The cells have capacity of 500 L/h disinfectant production and they have the ability to be run reverse polarity so that a self cleaning process takes place. Six of these cells are employed within the land based pilot BaWaPla system at Blyth-England on August 2009. The pilot system achieved IMO (International Maritime Organi-zation) standards and it is ready for IMO approval. Keywords: Ballast water treatment, electrochemical cell, chlorine generation.Balast tanklarında taşınan yabancı türler dünya gemi inşa endüstrisinin küresel boyuttaki en önemli çevresel problemlerinden birisidir. Bu problemin çözümüne yönelik olarak son 10-15 yılda birçok çalışma tamamlanmıştır. Bununla birlikte bu çalışmalar, kullanılan yönteme ve balast suyunda yer alan organizmalara bağlı olarak farklı sonuçlar vermektedir. Bu nedenle günümüzde gemi üzerinde balast suyu arıtımı konusunda yapılan çalışmaların çoğu birden fazla yöntemin bir arada kullanıldığı karma sistemler üzerinde yoğunlaşmaktadır. Klor gerek içme suyu dezenfeksiyonunda kullanılan en eski ve en genel yöntem olması, gerekse büyük hacimlerdeki sularda istenmeyen organizmaları gidermede de kullanılabilmesi nedeniyle balast suyu dezenfeksiyonu için önemli bir alternatif oluşturmaktadır. Ancak başta klor olmak üzere, dezenfektanların gemi üzerinde depolanması ve kullanılması gemi ve mürettebat güvenliği açısından riskler içermektedir. Diğer taraftan Cl2 gazı HOCl olmak üzere çeşitli dezenfektanların elektrokimyasal olarak üretimi gün geçtikçe önem kazanmakta ve balast suyu arıtımı için de alternatif haline gelmektedir. Bu çalışma Avrupa Birliği 6. Çerçeve Programı tarafından desteklenen 031529 kontrat numaralı araştırma projesi BaWaPla (Sustainable Ballast Water Management Plant) sonunda hayata geçirilen filtre, UV ve elektrokimyasal teknolojilerin bir arada kullanıldığı karma sistem için elektrokimyasal hücrelerin geliştirilme ve optimizasyon aşamasındaki laboratuvar çalışmalarının bir kısmını içermektedir. 3.5 yıllık Proje süresinin iki yıllık dönemde birbirinden farklı şekilde tasarlanmış 5 elektroliz hücresi farklı çalışma koşullarında test edilmiştir. Laboratuvar çalışmalarının sonuçları dikkate alınarak yeni bir hücre tasarımı gerçekleştirilmiş ve işletim parametreleri belirlenmiştir. Geliştirilen hücreler, Ağustos ve Eylül 2009’da Blyth-İngiltere’de kurulan büyük ölçekli pilot sistemde de kullanılarak test edilmiştir. Gerçekleştirilen testlerde IMO (International Maritime Organization-Uluslararası Denizcilik Örgütü) tarafından imzaya açılan “Gemilerin Balast Suları ve Sedimanının Kontrolü ve Yönetimi” sözleşmesinde yer alan deşarj standartları sağlamıştır. BaWaPla sistemi, IMO onayına hazır durumdadır. Anahtar Kelimeler: Balast suyu arıtımı, elektrokimyasal hücre, klor üretimi
Mikrobiyel yakıt hücresinde Shewanella putrefaciens tarafından organik atıklardan elektrik üretimi
Full text linkA microbial fuel cell (MFC) is a bioreactor that converts chemical energy in the chemical bonds in organic compounds to electrical energy through catalytic reactions of microorganisms under anaerobic conditions. Typical two chambered MFC systems are consist of conductive anode (such as carbon cloth or carbon paper) and cathode material (with platinum), proton exchange membrane (PEM), anolyte and catholyte, external conductive wire, and digital multimeter system and computer. In a MFC, power can be generated from the oxidation of organic matter by bacteria at the anode, with reduction of oxygen at the cathode. Anodic and cathodic chambers partitioned by a PEM. A bacterium in the anode compartment transfers electrons obtained from an electron donor (e.g. glucose, acetate) to the anode electrode. This occurs either through direct contact (nanowires) or mobile electron shuttles. During electron production protons are also produced in excess. These protons migrate through the PEM into the cathode chamber. Electrons can be also transferred to the anode by electron chemical mediator. But the toxicity and instability of synthetic mediators limit their applications in MFCs. Shewanella putrefaciens is bioelectrochemically active and can form a biofilm on the anode surface and transfer electrons directly (without mediator) by conductance through the membrane. When they are used, the anode acts as the final electron acceptor in the dissimilatory respiratory chain of the microbes in the biofilm. S. putrefacience was grown on LB broth. For aerobic growth, cultures were shaken continuously on a cooling rotary shaker-incubator at 160 rpm at 25°C. For anaerobic growth, approximately 1.25 liter of anaerobically prepare (in the athmosphere controlled chamber) LB broth in glass bottle was inoculated with 12.5 mL of an aerobically grown overnight culture and incubated without agitation. After 96 h of growth, the cells will be harvested under anaerobic conditions by a continuous centrifugation system at 4800 rpm at 4°C. The cell paste will be washed three times in 50mM sodium phosphate buffer containing 0.1 M NaCl . The washed cells was re-suspended in the buffer and transferred to 100 mL capacity anode compartment of the MFC on anaerobic conditions. The two chambered microbial fuel cells (TCMFC) were constructed using two glass bottles. Each bottle's volumes were 100 mL. Each cell compartment had three ports at the top, for electrode wire, addition and sampling of solutions, and gassing. Two compartments were separated by a PEM. The anode compartment was loaded with freshly prepared bacterial suspension (suspended in 50 mM Na-phosphate buffer (pH 7.0) containing 0.1 M NaCl, vitamin, mineral solution and substrate (acetate, ethanol and propionic acid). The cathode compartment was loaded with 50 mM Na-phosphate buffer (pH 7.0) containing 0.1 M NaCl. Nitrogen and air were continuously purged through anode and cathode compartments to maintain anoxic and aerobic conditions, respectively (flow rate of nitrogen gas was approximately 15 mL per min). The microbial fuel cell was immersed in a water bath to maintain temperature (25°C). Cooler was used to supply for summer conditions and heater was used to supply for winter conditions. The air conditioner was also used to supply constant temperature. Voltage (V, volt) or current (I, amper) was measured using a multimeter with a data acquisition system. Power density (mW/m2) was calculated according to P=Current*Voltage /projected area of the anode (P= IV/A.) When the anode compartment of the microbial fuel cells were loaded with freshly prepared S. putrefaciens, potential development was measured under open circuit conditions. Before the fuel (carbon source) was added, open circuit voltage (OCV) approximately 100-200 mV were observed from the microbial fuel cell containing suspensions of S. Putrefaciens. The addition of substrate as the fuel to the cell containing S. Putrefaciens resulted in a rapid rise in OCV up to 780-840 mV. Maximum OCV observed 832 mV, 777 mV and 810 mV for 10 mM glucose centrifuged from anaerobic growth of 1250 mL, 2500 mL and 800 mL from pure culture, respectively. The addition of ethanol was OCV up to 670 mV and addition of propionic acid was OCV up to 803 mV. A membrane MFC inoculated with S.putrefaciens and the circuit was completed with a fixed load of 5000 W were used to determine the power generation as function of load. 10 mM glucose produced 4 µA current. Power density was 0.8 mW/m2. Keywords: Microbial fuel cell, electricity production, Shewanella putrefaciens, voltage, power density. Mikrobiyal yakıt hücreleri (MYH) oksijensiz ortamda elektrojen mikroorganizmaları biyokatalizör olarak kullanarak organik maddelerden elde edilen kimyasal enerjiyi doğrudan elektrik enerjisine çeviren sistemlerdir.Tipik bir MYH’si anot, katot, proton geçirgen membran ve voltaj yada akım değerlerini ölçen veri toplama cihazından oluşur.Elektrojen bakteri oksijensiz ortamda anot üzerinde biyofilm tabakası oluşturarak organik maddeleri, karbondioksit, elektron ve protona çevirir. Bu çalışmada, iki hazneli MYH ve saf kültür Shewanella putrefaciens kullanılmıştır. Bu saf kültür bakterisinin seçilmesindeki amaç, dış membran enzimlerini doğal olarak kullanma yeteneğinde olduğundan elektronlarını iletken bir anota verme kabiliyetine sahip olmasıdır. Böylece bakteri tarafından üretilen elektronları anot elektroduna iletecek dışarıdan kimyasal bir medyatör kullanma gerekliliği ortadan kalkmıştır. Bu çalışmada, MYH’de farklı organik maddelerden ve farklı miktarlarda çoğaltılan saf kültür S. putrefaciens kullanılarak açık devre voltajları ölçülmüştür. 10 mM glikoz kullanılarak 1250 mL besi maddesi içinde çoğaltılan saf kültürün santrifüjünden elde edilen devre voltajı 832 mV iken, 2500 mL saf kültür için 777 mV, 800 mL saf kültür için ise 810 mV olarak ölçülmüştür.10 mM etanol kullanılarak 1250 mL saf kültürden 670 mV, 10 mM propiyonik asit kullanılarak 1250 mL saf kültür için ise açık devre voltajı 803mV bulunmuştur. Besi maddesi olarak 10 mM glikoz kullanıldığında 5000 Ω dış direnç ile çalıştırıldığında amper değeri 4 µA ölçülmüştür. Güç yoğunluğu olarak 0.8 mA/m2bulunmuştur. Anahtar Kelimeler: Mikrobiyal yakıt hücresi,elektrik üretimi, Shewanella putrefaciens, voltaj, güç yoğunluğu
Kuzey Anadolu Fay Sistemi Güney Kolunun Geyve-Gemlik arasındaki kesiminin tektonostratigrafik evrimi
Full text linkStrands of the North Anatolian Fault System (NAFS) in the Marmara Region were re-named within the content of this Ph. D. thesis. This fault system has been defined as horse-tail splitting into three strands as the Northern Strand of the North Anatolian Fault System (NAFSNS), Southern Strand of the North Anatolian Fault System (NAFSSS) and Southern-a Strand of the North Anatolian Fault System (NAFSSS-a). Lithostratigraphy, morphotectonic features, structural geology, basin models and historical earthquakes of the region were studied by this study for the Geyve-Pamukova and İznik basins located between Geyve (Sakarya), Mekece (Sakarya), İznik (Bursa) and Gemlik (Bursa) on the NAFSSS and bordered by the Armutlu-Ovacık Zone in north and the Sakarya Zone in south. Six main faults (Sarıgazi, Mekece, Dırazali, Gürle, Orhangazi, Umurbey) and three fault zones developed by the secondary segments related to the six main faults were mapped as the NAFSSS in the region. The Sarıgazi main fault in the east of the study area and in the Geyve-Pamukova basin and the Geyve Fault Zone (GFZ) were created by the secondary segments. Deposits of the Geyve-Pamukova basin were mapped based on the lithostratigraphic facies. The units from the bottom to the top of the basin were classified into four formations as Geyve (Qg), Pınarlı (Qp), Çardak (Qc) and Hocaköy (Qh). The Geyve formation was divided into Kollu pebblestone (Qgk) and Beylik clastic (Qgb) members and Çardak formation was sub-divided into Ayvalık (Qga) and Yanıkorman (Qcy) clastic members. The Kollu pebblestone member deposited at the base of the Geyve-Pamukova basin is a debris-flow deposit. The source for this member is Sakarya River and its small tributaries.Beylik clastic member of the Kollu pebblestone defines channel and set-point enviroments of the same river. The present deposition of these units in the southern edge of the basin is directly related to the deformation caused by the right lateral displacements by the Sarıgazi fault in Sakarya River. Alluvial fan Hocaköy formation overlies these basal units with uplifting of southern block by the Sarıgazi fault. The southern edge of the basin is formed by the right lateral fault. However, flood-plain sediments of the Pınarlı formation are deposited on the northern edge, where the deformation effect is less. The youngest unit is the Çardak formation located in the middle of the basin. This formation resembles to the Geyve formation. Architecture of the Iznik Basin along the NAFSSS developed when the step-over of the northwesterly striking Dirazali fault to Gurle fault triggered westerly step-over of the Gurle fault to east-westerly striking Umurbey fault due to simple dextral shear kinematics and north-nortwesterly, south-southwesterly transtensional deformation. This basin architecture was also supported by the southerly dipping, dextral oblique Orhangazi fault that is identified at the northern edge of the Iznik fault. The vertical displacement of southern edge of the basin by the right lateral faulting caused disconnections to the sea level. As a result, the İznik formation was deposited in a brackish water environment. After the sedimentation phase in the basin, the dominant right lateral oblique movement of the Gurle fault located between the Umurbey and Dırazali faults elevated the İznik formation approximately 60 m from the basin surface. Additionally, the Orhangazi fault which has the same charter as the Gurle fault controlled the İznik and Hocaköy formations located in the western section of northern edge of the basin. The slickenlines pointing out a right lateral oblique normal faulting indicate a rotation with simple shearing and transtension for the right lateral fault system. The basin was formed as lazy S shaped pull-apart basin that was created by the right lateral faulting and NNE-SSW dilatation. This neo-tectonics shows that the İznik basin is a pull-apart basin developed with a transtensional right lateral faulting. Almost all of the structural features of the right lateral simple shearing strain elipsoid were developed during the all stages of the basin opening. Keywords: Southern Strand of the North Anatolian Fault System, Tectonostratigraphy, Lazy S shaped pull-apart basin.Kuzey Anadolu Fay Sistemi güney kolu üzerinde neotektonik dönemde oluşan düzlük alanlar birbirine Mekece-İznik koridoru ile bağlanan Geyve-Pamukova ve İznik Havza’larıdır. Geyve-Pamukova Havza’sının litostratigrafisi alttan üste doğru; yanal geçişli Geyve-Pınarlı, Hocaköy ve Çardak formasyonlarını içerir. Hocaköy formasyonu güney bloktan gelen drenajın, Geyve formasyonu ise Sakarya Nehri’nin desteği ile oluşmuştur. Bunun yanında Sakarya Nehri’nin havza açılımından günümüze değin uğradığı sağ yanal atımlı deformasyon Geyve formasyonunun gelişmesinde birincil etkendir. İznik Havza’sında ise Erken Khazarian’dan günümüze alttan üste doğru İznik, Hocaköy ve Solöz formasyonları çökelmiştir. Geyve-Pamukova Havzası güney kenarındaki KD-GB doğrultulu sağ yanal atımlı Sarıgazi Fayının açılmalı dönmesi sonucunda gelişmiş gevşek S biçimli çek-ayır havza şeklinde oluşmuştur. İznik Havzası ise güney kenarındaki KD-GB doğrultulu sağ yanal atımlı Dırazali fayının, BKB-DGD doğrultulu sağ yanal oblik bir normal fay olan Gürle fayına sıçraması ile birlikte oluşmaya başlamıştır. Havzanın kuzey kenarındaki KB-GD doğrultulu sağ yanal oblik normal fay karakterli Orhangazi fayı ise havzanın Geyve-Pamukova Havzasına göre daha simetrik açılmasına destek olmuştur. İnceleme alanının bütününe hakim olan sağ yanal basit makaslamalı sistem İznik Havza’sının ise daha geniş ölçekli çek-ayır havza şeklinde açılmasını sağlamıştır. Anahtar Kelimeler: Kuzey Anadolu Fay Sistemi Güney Kolu, Tektonostratigrafi, Gevşek S biçimli çek-ayır havza. 
Data sources:
Access Repository Dashboard
Do you manage itüdergisi (E-Journals - İstanbul Teknik Üniversitesi, Istanbul Teknik Uniersity., İTÜ)? Access insider analytics, issue reports and manage access to outputs from your repository in the CORE Repository Dashboard!