Jeosentetikler ve karayollarında kullanımı
Başlık çevirisi mevcut değil.
- Tez No: 75287
- Danışmanlar: PROF. DR. EMİNE AĞAR
- Tez Türü: Yüksek Lisans
- Konular: İnşaat Mühendisliği, Civil Engineering
- Anahtar Kelimeler: Belirtilmemiş.
- Yıl: 1998
- Dil: Türkçe
- Üniversite: İstanbul Teknik Üniversitesi
- Enstitü: Fen Bilimleri Enstitüsü
- Ana Bilim Dalı: İnşaat Mühendisliği Ana Bilim Dalı
- Bilim Dalı: Ulaştırma Mühendisliği Bilim Dalı
- Sayfa Sayısı: 176
Özet
ÖZET Taşıma gücü düşük zeminler üzerine inşa edilen yollarda inşaat süresince ve kullanım sırasında oluşan deformasyonlar büyük problem olmaktadır. Bu problemleri çözebilmek için yeni malzemelerin ve yapım tekniklerinin geliştirilmesi amacıyla yoğun çalışmalar yapılmıştır. Yapılan çalışmalar sonucunda gelinen son aşama sentetik kumaşlar yani jeosentetiklerdir. Bu çalışmanın amacı, ülkemizde yeterince bilinmeyen jeosentetikleri daha iyi tanıtmak, kullanım alanları özellikle de karayollarındaki kullanımı hakkında bilgi vermektir. Çalışmada, jeosentetikler yedi bölüm halinde incelenmiştir. Birinci bölümde jeosentetiklerin ortaya çıkışı ve gelişimi anlatılmıştır. İkinci bölümde jeosentetik üretiminde kullanılan hammaddeler, bunların özellikleri ve temel iplik çeşitleri hakkında bilgi verilmiş, konuyla ilgili tanımlar yapılmıştır. Üçüncü bölümde ise, jeotekstil, jeomembran, jeogrid ve ve jeonet gibi malzemelerin üretim teknikleri, özellikleri ve satış miktarları verilmiştir. Jeosentetiklerin hidrolik ve mekanik özelliklerinin belirlenmesi amacıyla yapılan deneyler dördüncü bölümde anlatılmıştır. Jeosentetikler zeminin desteklenmesi için, filtrasyon, drenaj için, kıyıların ve deniz yataklarının korunmasında erozyon kontrolünde ve daha pek çok alanda başarıyla kullanılmaktadır. Beşinci bölümde kullanım alanları ana hatlarıyla özetlenmiştir. Altıncı bölüm jeosentetiklerin karayollarında kulanımını içermektedir. Karayollarında ayırma tabakası, filtre malzemesi üst yapıyı destekleyici ara tabaka olarak kullanılan jeosentetiklerin dolguların yapısal stabilitesini artırdığı ve yansıma çatlaklarım önlediği de bilinmektedir. Jeosentetik malzemenin davranışının zemin ve jeosentetikler arasındaki ilişkinin tam olarak anlaşılamaması bul malzemenin klasik projelendirme yöntemleri içerisine dahil edilmesini güçleştirmiştir. Bu bölümde Giroud ve Sellmeijer tarafından geliştirilen tasarım yöntemleri yer almaktadır. Giroud, tasarımda klasik zemin mekaniği kabul ve yöntemlerini kullanırken, Sellmeijer jeotekstilin işlevine uygun parametreleri kullanan tasarım yöntemleri geliştirmiştir. Bu bölümde ilgili parametreler de detaylı olarak verilmiştir. Yedinci ve son bölüm ise, sonuçlar ve önerilerden oluşmaktadır. Jeosentetik kullanılarak inşa edilen yolların ömrü ve performansmdaki artış, jeosentetiklerin malzemeden sağladığı kazanç ihmal edilemez boyutlardadır. Bu yüzden de kullanılan miktarlar her yıl büyük oranda artmaktadır. Buna rağmen ülkemizde bu konuda yapılmış detaylı bir çalışma yoktur. Bazı kuruluşlar yabancı ülkelerdeki şartnameleri inceleyerek sınırlı içeriğe sahip şartnameler hazırlamışlardır. Bunlar daha detaylı hale getirilmelidir. XIX
Özet (Çeviri)
SUMMARY GEOSYNTHETICS AND APPLICATIONS IN HIGHWAYS The development and utilization of geosynthetics in subsurface construction work has been widespread. These products have risen from a relatively minor and specialty-product status to a worldwide in last twenty-year period. No other spesific class of items in civil engineering and related construction activites has had such a dramatic increase in so short time span. The current stuation is both exciting, due to the newness and unknown challenges posed by the products, and dangerous, due to the obvious uncertainties involved. Engineers and contractors have tried to reinforce soft soils with dissimilar materials and then polymeric materials emerged. At first, plastic materials that have poor initial performance have been used in the 1950 s. Consisting almost entirely of people other than civil engineers have sensed the need for such a material, developed the products and have done so in an open and competitive mannner. The future of geosynthetic products seems very strong for continued growth merely by extending the present situation. If new concepts involving threads, spirals,tubes and other shapes come into being and are combined with themselves or with existing synthetic materials, an entirely new thrust will most likely occur. Compeletely new application areas might result as well as extending those that exist. The resulting impact could well be as dramatic as in the recent past. The future for geosynthetics is indeed a bright one. The reason for this rapid development of new products are numerous and include the following: - They can be installed rapidly. - They replace raw material resources. - They replace difficult designs using natural materials. - Their timing is very appropriate. - Their use is required by law in some cases. The professional groups most strongly influenced are geotechnical engineering, heavy construction, building construction, hydrogeology and environmental engineering although all soil-and rock-, and groundwater-related activites fall within the general scope of various applications. Geosynthetic materials perform five major functions; reinforcement, filtration, drainage and moisture barrier. The use of geosynetics has basically two aims: to do the job better (with no deterioration of material or excessive leakage) and to do the job more economically (either through lower initial cost or through greater durabilitiy and longer life, reducing maintenance cost). The spesific families of geosyntetics are follows : Geotextiles Geogrids Geonets XX- Geomembranes - Geocomposites Geotextiles form the largest group of geosynthetics. They are indeed textiles in the traditional sense but consist of synthetic fibers, rather than natural ones. These synthetic fibers are made into a flexible porous fabric by standart weaving machinery or are matted together in a random, or nonwoven manner. Some are also knit. There are at least 80 spesific application areas for geotextiles that have been developed, however, the fabric always performs at least one of five discret functions: - Separation - Reinforcement - Filtration - Drainage Moisture barrier. Geogrids represent a small but rapidly growing segment of the geosynthetics area. Rather than being a woven, non woven or knit textile fabric, geogrids are plastics formed in to a very open gridlike configuration. They have large apertures. Usually, they are streched in one ore two directions for improved physical properties. By themselves, there are a lot of application areas and they function in two ways: separation and reinforcement. Geonets constitue another specialized segment of the geosynthetics area. They are usually formed by a constinuous extrusion of polymeric ribs at acute angles to one another. When the ribs are opened, relatively large apertures are formed in a netlike configuration. Their desing function is completely within the drainage area where they have been used to convey fluids of all types. Geomembranes represent the second largest group of geosynthetics. The materials themselves are“impervious”thin sheets of rubber or plastic material used primarily for linings and covers of liquid-or solid-storage facilities. Thus the primary function is always as a liquid or vapor barrier. Geocomposites consist of a combination of geotextile and geogrid; or geogrid and geomembrane; or geotextile, geogrid, and geomembrane; or any one of these three materials with another material. This area brings out the best creative efforts of the engineer, manufacturer and contractor. The scope of this study at first, to explain where or how geosynthetics are used, and second the use of geosynthetics in unpaved or paved roads.Development of synthetic materials is given in Chapter 1 and also primarily applications of these materials for different purposes are summarized in this chapter. In Chapter 2, the information about the raw materials used in production of geosynthetics, is given. Polyamide, polyester, polyethylene, polyproplene, polyvinly chloride, ethenecopolymer bitumen and chlorinated polyethylene are used for production of those materials. Some information about the yarn manifacture are also given in Chapter 2. Types and production technologies of geosynthetics is given in Chapter 3. High technology an experience is necessary for production of these synthetic fabrics. The geosynthetics, properties reguired stem from the function it must be fulfil. Since the geosynthetics can have a variety of functions-reinforcement, filter, draining, separation layer-the primary functional reguirements are diverse. For Reinforcement, the emphasis is on mechanical properties such as E modulus and strenght for filters it is on hydraulic properties such as water permeability and soil xxitightness. Geosynthetics must also fulfil secondary functional requirements related to the execution of the work, e.g. a certain amount of UV resistance is needed, or it must have resistance to mechanical wear and tear when construction equipment is to be expected to drive over the fabric. The suitability of a geosynthetic should be checked againts these functional requirements during the design of a civil engineering construction. In principle, performance or qualification tests need only be executed once, unless there is an essential change in the mater of the geosynthetics or its production process. The tests for geosynthetics is detailed in Chapter 5. If necessitated by the functional requirements these tests can be relatively complicated and the testing time relatively long. The quality of the test is essential, particularly in its relationship to required properties under site conditions. In order to be sure of the constant quality of a geosynthetics it is necessary to subject it to guality control tests reqularly, they so- called index tests. Sometimes performance tests are too expensive and time- consuming to be used for quality control testing. Another object of these tests can be to identify the elements of fabric or the fabric itself. The properties of a geosynthetic are depedent on the properties of the fibres, being the elementary structure elements, and of the fabric construction referred to as the structure of the geosynthetic. So, when considering the properties of a geosynthetics, it is important to consider the properties of the materials from which the fabric is built up. Standard methods of testing are needed for determining the various geosynthetic properties and a large number of test methods have been standardized in certain countries. A number of international organizations have laid down standards for some methods of testing (EDANA, DIN, ASTM...) Different applications of geosynthetics are outlined in chapter 5. Geosynthetics are used in roads and highways for different purposes. Those purposes and design methods for these purposes are given in Chapter 6.“Desing by function”appears to be accented bv manv designers.“Design bv function”is a concept whereby aWhen selecting a geotextile for a particular application, consideration should first be given to the aplication itself. The selection procedure adopted for a particular application is schematically, as follows : 1. Analysis of the construction in the light of existing technical criteria. 2. Description of the geotextile functions required and the related properties. 3. Quantification of the geotextile properties using desing methods. 4. Specification of the geotextile. 5. Selection of the geotextile. In this chapter design methods for different application developed by Sellmeijer, Noiray and Giroud is explained. Sellmeijer has used some parameters related to the function of synthetic fabrics mentioned above. Giroud and Noiray have developed design charts. They have used standart axle pass and CBR value of the soil. They have calculated subgrade thickness with or without geotextile. The difference between these values gives the saving that geotextile causes. In this chapter some information about the geosynthetic interlayers in asphalt overlays is given. Crack formation in the lower part of the asphalt is mostly induced by thermal stresses or traffic loads combined with already existing shrinkage cracks in the cement treated base layers of the structure or with abrubt transitions between different types of founddations. Cracks can initiate at the surface as well in the case of rapid cooling down of the top layer creating a serious temperature gradient over the thickness of the structure. When the constructive contribution of the asphalt layer to the stiffness of the total construction decreases, this results in to an increase in the loading of the underlying base and sub-base. This can lead to a local failure of the base construction. This can finally lead to a complete rupture of the asphalt layer. The process will be accelerated by the ingress of water causing a softening of the base and sub-base and causing pumping. The only sufficient solution in such a case is to remove all elements and replace them by materials which sufficient bearing capacity. Overlays on a completely ruptured construction will soon lead to vertical movements and reflective cracking due to stress concentrations at the location of the cracks. A possible method to limit the continuaton of crack in new asphalt overlays can be the application of geosynthetic interlayers between old and new asphalt. Possible functions of these interlayers are : - To relase or absorb the stresses in the asphalt via a slip layer. - To increase the structural strenght of the asphalt overlay by reinforcement. - To act as a water barrier, protecting the old asphalt or concrete and base layers against the ingress of water via newly appeared crack overlay. Various types of interlayers, different by function, material, appereance and performance, are available. Flexible materials may allow a better bond between old and new asphalt than rigid in the case of uneven old asphalt surfaces. Open materials ( grids and nets) allow interlocking and therefore better bonds between old and new asphalt. Conclusions are given in Chapter 7. In this chapter the savings that geosynthetic causes, production and use of this material in our country is explained. The specifications that T.C.K. uses are also critized in this chapter. Today this materials XXU1are used sucessfully in abot of area. This study consists of some basic information about these materials and their applications. XXIV
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