Yeni bir inşaat malzemesi olarak geotekstiller
Geotextiles as a new construction material
- Tez No: 66644
- Danışmanlar: PROF. DR. REMZİ ÜLKER
- Tez Türü: Yüksek Lisans
- Konular: İnşaat Mühendisliği, Civil Engineering
- Anahtar Kelimeler: Belirtilmemiş.
- Yıl: 1997
- Dil: Türkçe
- Üniversite: İstanbul Teknik Üniversitesi
- Enstitü: Fen Bilimleri Enstitüsü
- Ana Bilim Dalı: Geoteknik Mühendisliği Ana Bilim Dalı
- Bilim Dalı: Belirtilmemiş.
- Sayfa Sayısı: 130
Özet
ÖZET Geotekstiller, sağladıkları teknik olarak avantajlı, maliyet olarak düşük olan çözümlerle inşaat mühendisliği konulan içerisinde önemli bir yer tutmuşlardır. Yüzyılımızın ortalarında tekstil sektöründe pazar daralması ve tekstil üreticilerinin yeni pazar imkanları arayışıyla, geotekstüler inşaat mühendisliği sahasında yaygınlaşmaya başladıysa da daha sonra geleneksel inşaat malzemelerine ve uygulamalarına alternatif olmuşlardır. Büyük gelişme ise sentetik fiberlerin keşfiyle olmuştur. Başlangıçta sınırlı sayıda olan uygulama sahaları günümüzde çok artarak özel uygulama sahaları oluşmuştur. Geotekstiller teknik ve tasarım yönünden baş döndürücü bir hızla çeşitlenirken, bu gelişmelerin son noktasının insanın hayal gücüyle ancak sınırlı olduğunu söylersek abartmış sayılmayız. Geotekstillerin uygulama sahalarının ve üretim tiplerinin tüm Dünya 'da büyük bir hızla artıyor olması beraberinde bazı sorunlarda getirmektedir. İlk akla gelenleri şunlardır: - İletişimin, geotekstillerdeki yeniliklere paralel olarak gelişememesi gerek uygulayıcılar gerekse tasarımcılar tarafından yetersiz bilgilenmeyi beraberinde getirmektedir. - Ülkeler arasında ortak standartlar oluşturulamamakta, ülkeden ülkeye hatta bazen aynı ülke içinde dahi aynı tip uygulamalar için farklı standartlar olabilmektedir. Deney yöntemlerindeki farklılıklar sonuçların değerlendirilmesini güçleştirmektedir. - Çok fazla miktarda geotekstillerle ilgili terim yada isim oluşmaktadır. Birbirinden bağımsız olarak üretilen ürünler için üreticiler farklı isimler kullanmaktadır. Bu da bilgilenmeyi yavaşlatmaktadır. Ülkemiz açısından konuyu ele aldığımızda geotekstillerle ilgili terimlerin pek çoğunun henüz Türkçe karşılıkları bulunmamaktadır. Geotekstillerlerin davranışlarım açıklayabilmek için üç tür çalışma yapmaktayız : l)Gözlemler; geotekstilin belirli şantiye koşullarında uygulanarak değişikliklerin kaydedilerek değerlendirilmesidir. Ancak bu çalışmalar uzun zaman ve yüksek maliyet alabilmektedir. 2)İndeks Deneyleri; laboratuvarlarda izole edilmiş koşullarda yapılan, genellikle geotekstillerin kendi aralarında özelliklerinin mukayese edilmelerini sağlayan deneylerdir. 3)Performans Deneyleri; laboratuvar deneylerinin izole koşullarıyla arazi gözlemlerini dengeleyerek kullanan deneylerdir. Bu deneylerden elde edilen sonuçlar tasarımda kullanılmaktadır. Sonraki bölümde geotekstille tasarımda dikkat edilmesi gerekilen noktalar anlatılarak farklı tasarım yöntemleri mukayese edilmiştir. Tezimiz kapsamında ele aldığımız diğer bir konu da geotekstillerin filtrasyon maksadıyla kullanılmalarıdır. Bu amaçla geotekstil filtrelerin çalışma mekanizmaları incelenmiş, mineral filtrelerle geotekstil filtreler teorik ve pratik olarak karşılaştırılmış ve geotekstil filtrelerin bazı kullanım sahaları incelenmiştir. VI
Özet (Çeviri)
GEOTEXTILES AS A NEW CONSTRUCTION MATERIAL After thell.World War, as a result of the decreasing demand and competition, western textile producers started to search for the new markets including civil engineering sector. At the very begjning, although fabrics entered to the area of civil engineering, later geotextiles became alternatives to the traditional construction materials. After that, geotextiles for special aims were started to be developed and they became world wide common civil engineering material. Geosynthetics term states geotextiles, geomembranes and related materials used in civil engineering. However, there are also unsynthetic geotextiles. Geoproduct term maybe a more inclusive term. As a result of high speed in production technologies and different techniques, these products can have many different names. Therefore, although there are not the common Turkish correspondences of their names, Yetimoğlu's [2] studies made for this reason. Geotextiles are used for four main reasons in civil engineering, 1) filtration, 2) drainage, 3) separation, 4) reinforcement. But in a situations, one of these functions becomes primary while other functions are supportive. Another out of the high developments in geotextiles industry is the lack of the standards. While many of the geotextiles standards came through textiles industry, there are not international standards. In every country, even in the different entities of the countries chose the alternative of making their own standards. The first study to internationalize the different standard was made by ISO in 1985. Although geotextiles usage is getting increased day by day, there is still a point of view seeing the usage of geotextiles as an additional cost. If this point of view was true, it would not possible to usage. Geotextiles industry is not just related to civil engineering but also environment, chemistry and plastic industries. The aim of this study is to widely define especially the nonwoven geotextiles which became more and more common in Turkish civil engineering sector, to point out the factors which need to be taken into consideration, to enlighten the desings which would be made by using geotextiles, to explain especially the filtration function which has a common usage by paying attention to hydraulic specialties of geotextiles. XfflThe first serious development in geotextiles realized by the production of synthetic fiber with raw materials. The usage of geotextiles in the“Delta Project”developed to prevent very serious float disasters in the southwest Holland in 1950's is another step in usage of geotextiles with new techniques. The materials used in foreign constructions firms' projects until the last years in Turkey are also placed widely in the Turkish engineer and contractors projects lately. Geotextiles find application areas in almost all construction projects and demand for these multi functional materials is getting increased by time. The utilities of geotextiles were realized easily by engineers, designers and contractors. For example, granular filters were replaced with geotextiles for the reasons of filtration. Their properties to show strength to tensile stress, to be easily applicable, difficulty of the construction of granular filters, to be homogeneous and controllable easily because of fabrication provide important advantages. Moreover instead of carrying tons of granules and earth works, it provides saving to carry a few rolls of geotextiles. The application easiness, increased construction life, easiness of quality control are the very satisfactory factors provided by geotextiles usage. Besides this, not factors like enough communication among geotechnical engineers, getting inadequate in formation and not enough spread of standards, in design and application, a half century summation is existent. Fiber or flaments, which form the structure of geotextile, are produced off 4 main polymer raw materials: Polypropylene ( % 65 ) Polyester ( % 32 ) Polyamide (%2 ) Polyethylene ( %1 ) Among geopolymers, the most commonly used ones are polypropylene with %65 usage and polyester with %32 usage. Chemical properties of polymer raw materials are different from each other. Properties of raw materials have a major effect on geotextile. Polyester has high modules and greatly resistant to creep. It keeps its mechanical properties in high temperatures and shows resistance to sea- water, acids, microorganisms and sun rays. Polyamide, is resistant to erosion and burning. While is sensitive to liquid environments. Porypropylen and polyethylene show great resistance to chemicals that are at low and medium concentrations. These are sensitive to creep and burning. Geotextiles can classified according to formation techniques, polymer bonding, its weight and engineering functions. There are two main ways in classifying according to formation technique : 1) Woven Geotextiles 2) Nonwoven Geotextiles These can also be grouped according to fiber types. While woven types can be grouped as with monofilament, multifilaments, split film etc. non woven types can xrvbe grouped as melt-bonded, resin-bonded or needle punched in a certain environment or in random organization. There are two main factors effecting the quality of nonwoven geotextile 1) Type of the raw material (type of the fiber) 2) Production technique The most commonly used method, that is needle punched which is the most commonly used method is slow, it allows us to have strong and high gramage forms. During production of geotextiles, we can add certain chemicals that are convenient to its structure so that we can make the deceived properties better. In our country, nonwoven geotextile can be produced 6.5m width joint with is important in usage of adding width. Approximately 50 cm width joint must be made in addition point. Woven geotextiles, are produced in traditional multiyarns, split films Generally, both in two methods, they display high tensile stress and low strain. Woven textiles may have different knitting techniques. Besides these knitted geotextiles are formed by a series of knits being linked to each other. Combination geotextiles are being made off methods like gaps of woven geotextiles being filled by nonwoven types. In chapter 3, properties of geotextiles are being examined. These are, 1) Physical properties of geotextiles 2) Mechanical properties 3) Hydraulic properties 4) Degradation properties In determine these properties, experiments and observations, Which will form the base to comparison of geotextiles to each other and designs are being explained. Experiments that are made in determining properties of geotextiles are made up two groups : 1) Index experiments 2) Performance experiments Index tests are tests representing not the geotextile' s site conditions but its conditions under artificial environment conditions. All index tests are isolated from soil conditions. Tests in this group represent the special attitude of geotextiles in ground or basic conditions with other elements in the system. These elements are represented not by through environment conditions in the ground but by increase degrees in long run and safety limit in short run. The choice of the geotextiles which is wanted to be learned. The reasons of the failure are important to choose the right tests. Index tests can be controlled and calibrated by field tests. Limits are determined by these tests. But the changes in field conditions include many different possibilities. Although observation and experiences are not clear perfectly, their costs XVare high and they give information about the environment in short run. However they can be necessary for some applications. Performance tests fill in the blanks between index test performed in field conditions and field applications. The conditions in these tests are as similar as the conditions in the field. A difference of performance tests from index test is that they can be used without any modification. Physical characteristics of geotextiles could be stated as length, width, height, weight and unit volume weight. Geotextiles can be produced on a limited width but at any length. Their weights change in a range of 135 to 680 gr./m2 The tests that are used to determine their physical characteristics are available in the standards. Samples are observed in different soil and weather conditions and like differences in color, structure, physical degradation (tear, puncture...), chemical activity, clogging in filter usage are recorded. There differences can be observed more easily by electron microscope. As a degradation factor, degraded and undegraded some kind areas can be compared according to the percentage of holes or size of holes. But it is difficult to determine what affected degradation and undegradation and to determine in which ratio limit value is obtained. Therefore qualitative dates can be obtained more then qualitative dates by using observation. Creeping and stress release could be stated as their main characteristics. It is known that, polymers change their forms depending upon the time passed under forces of pulling and compression. Although the testing methods have not been standardized yet.We have enough information about the geotextiles behavior under load in a specific time upon. There are various studies about the creeping behavior in the literature but the same is not valid for stress release behavior. Nevertheless there is a complex relationship among these two behaviors. Although the test results are product-bounded, changeable by heat, produced under isolated conditions, they could be modified to the design. The creeping behavior of the geotextiles under soil, requires raw studies. Under conditions where the geotextiles are placed near the surface of the soil thermal resources or chemical and biological effects especially strengthening applications a high attention should be given. Another important condition which requires high attention is where especially nonwoven geotextue is pressed loads placed perpendicular to its surface. Compression decreases the liquid ttansmission along the surface of the Nonwoven geotextiles which are produced by chemical or mechanical methods.. Tension strength determines either the primary function of strengthening or the secondary function of drainage, separation and filtration. All of the types of tension strength tests give information on index or performance specifications. There is information on tension strength in every geotextiles producers catalogs and standards. From the tension strength tests ; 1) Maximum tension stress 2) Maximum deformation 3) Strength 4) Material modules, could be obtained. XVIGeotextiles with it is mass-production measures could not be suitable. In such cases the ends of large rolls of geotextiles have to be joined together at the factory or site. The most common method by sewing. However sewn seams must be tests for their load-transfer capability. Nevertheless there is not get a standard for this purpose. Burst, tear, puncture, impact strength tests are the effects on geotextiles ( for applications ) at, site conditions. Sharp riprap stones, concrete blocks, working machines or other stiff materials can cause impacts, puncture, tear or burst effects on surface of the geotextiles. One of the geotextiles hydraulic properties, porosity is explained the some as the explaining soil mechanics classical usage. Porosity is highly correlated to the liquid transfer capacity of geotextiles. However, because it is difficult to measure porosity alone, by means of the other features of the geotextiles, it is determined indirectly. Apparent opening size is a basic factor that determines the geotextiles filtration function and it is determined according to the values of 093 or O90. A.O.S is highly correlated to the permeability of soil geotextiles system. But the experimental techniques which determine A.O.S have insufficient sides. With the help of the latest developed tool, analysis with computer, it is determined not only 09J or O90 values of geotextiles but also all pore size spread. Permeability criterion is one of two criteria, determines basic functions of filtration in the calculation of permeability that is determines fluid flow perpendicular to the surface of the geotextile, we use Darcy's law. Permitivity will be determined to ignore thickness affect on the permeability in comparing different types of geotextiles. There is a load pressure at least due to self weight of the soil in site conditions. To represent this concept, geotextile is tested under the beams that is named permitivity test. Usually fluid ttansmission functions on the fluid surface, is utilized in the usage of geotextiles with purpose of drainage. Transmissivity, is the amount of fluid hydraulic gradient. Thick and nonwowen geotextiles is used to get more fluid transmission under the geotextile. Raw materials of geotextiles that are polymers are effected from high temperature differences, chemical substances, ultraviolet lights. For high temperatures, it should check degradation temperatures ; for low temperatures it should check brittle's in the lab, of raw material polymers. Geotextiles should be checked under the site conditions for the chemical or biological affects. Sunlight affects on the geotextile changes according to geographical locations so, geotextiles should test for geographical conditions. Polymer materials are effected by U.V lights, high radiation, ocsidation hydrolysis and chemical reactions. As for biological degradation, they can be prevented by high molecular weights. These affects can create more complex outcomes by means of heat, tension and mutual relationships. For example, it is known that heat increases the degree of all mentioned degradation types. The type of tension is important. Tensile, compressing, shear, torsion effects can create different results. The relationships between these affects need to be investigated. Although it is difficult to determine the degree of polymer degradation, it is known that xvndegradation cause the material to show britüeness and to decrease its flexibility feature. Chemical producers, raw material producers and geotextiles producers try to prevent polymer degradation. The developments in chemical resins are increasing the molecular weights of the polymeric materials. The limited polymer usage in geotextiles production cause the lack of the developments in production materials. Therefore quality control and production speed becomes more effective factors. Anti oxidation chemicals are used to prevent degradation in melting and extruding steps of geotextiles production and special chemicals are used to provide uniformity. It is difficult to forecast degradation times of the geotextiles which are formulated by special chemical methods, produced fabrication, placed and covered to the soil according to a special design. But it is known that this time is long enough to be accepted. Because of their high molecular weights, polymers used in geotextiles production shows expected durability to the degradation. Polymeric aging states lack of the engineering functions expected from this material According this point of view, half life of the geotextiles can be considered as the %50 decrease in the flexibility of the geotextiles. As can be seen, this approach is rather subjective and leaves the last decision to the designer engineer. It is stated that Arrhenius model is the best model to forecast polymer aging. In this study, filtration function of geotextiles is investigated in detail For this purpose, we studied more about clogging on the geotextile in long term flow. Especially, pores of nonwoven geotextiles can be clogged by means of the thin soil pieces carried from upstream side while flowing perpendicular to their surface. In the laboratory tests representing this situation gravel-geotextile-soil system is placed under flow with fixed or changing head of water. The change in the permeability coefficient is according to duration by the start of the flow or the flow rate of water recorded. At the experiments which used nonwoven geotextiles which was produced from polyester and needle punched bonded (weight of the geotextiles are 300gr/m2 and 150gr/m2) placed under the light brown clay with silt soil. The results of the experiments which last 15 days show the decreases in flow rate and permeability coefficient of the system. Because of the clogging in the pores of the geotextiles. Moreover it can be stated that the decrease in the flow rate quantity of 150gr/m2 weighted geotextiles more than 150 gr./m2 weighted geotextiles. In the fourth chapter, an approach of Koerner [12] is explained about design. One of the three approach is applied to evaluate different alternatives and decide the most suitable geotextile in a special geotextile application. 1) Design by specification 2) Design by cost and availability 3) Design by function Design by cost and availability is traditionally used but it is insufficient technically. While using design by specification, we compare the standards of various entities with the properties of the geotextiles we have. In this application, it must be taking into consideration that the values in standards are minimum values and therefore the minimum value of the possible geotextiles' s determined property must be compared. xvmDesign by function is more developed approach. According to this approach, a safety factor is provided by comparing the allowable property of the geotextile's for an application with the required property of the geotextile's. If the safety factor is more than 1 as wanted, it means that geotextile is suitable. Thus a technically suitable and economic choice is preferred. At the last chapter, fist of all theoretical explanation of the geotextile usage for the reason of filtration was made, and then different applications were mentioned. In the mechanism of the geotextile filter's, we face with a condition called bridging. Adjacent to the upstream side of geotextiles, big pieces come together and then while going away from geotextiles these pieces get smaller and the permeability of the soil decreases. Thus while a balance between the soil in upstream side and geotextile occurs, geotextile works only as catalyst which provides the occurrence of this system. Filtration is provided by soil filter in upstream side occurred itself. Later two steps of the theory used in geotextile filters design: 1) Retention Criteria 2) Permeability Criteria were explained with examples of geotextile filters usage behind retaining walls, Around under drains, beneath erosion control structures and silt fences etc.
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