Tünel açma işlemleri,karşılaşılan sorunlar ve uygulanan çözüm yolları

Abstract

Bu çalışmanın içeriği, tünel açma faaliyetlerine bağlı olarak, oluşabilecek sorunların belirlenerek bunların çözümüne olanak sağlayacak olan işlemleri kapsamaktadır. Çalışmada sorunlar öncesinde dünya üzerinde başlangıcından günümüze değin tünelciliğin tarihçesi ve gelişimi sunulmaktadır. Tarihsel sıraya göre tünel açma çalışmalarının kimler tarafından yapıldıkları belirtilmiştir. Daha sonra tünel makinelerinin icad edilmesinden, günümüze kadar olan evrimine genel bir bakış yapılmıştır ve geleceğin makinelerinden bahsedilmiştir. İnceleme, ilkel tünel makinelerinden günümüz modern tünel makinelerine (TBM, Roadheader, Mobil miner, Darbeli çekiç) doğru yapılmıştır. Ayrıca son model tünel makinelerinin teknik özellikleri ve performansları hakkında detay bilgiler verilmiştir. Dünyada ve Türkiye'de tünelciliğin gelişimine paralel olarak açılan tünel uzunlukları tablolar halinde verilmiştir. Tünel açma maliyetlerine kısaca değinilmektedir. Tünel açma işlemlerinde ağırlıklı olarak kullanılan NATM yöntemi ilkeleriyle açıklanmıştır. Değişik zeminlerde en uygun iksa tipinin ve aralıklarının saptanmasında kullanılan metodlar açıklanmaktadır. Tüm açıklamaların nihayetinde kazı sırasında oluşan sorunlar ele alınmaktadır. Karşılaşılan sorunlar oldukça fazladır. Tünelin açıldığı formasyonun özelliklerine bağlı olarak sorunlar farklılıklar göstermektedir. Fakat genel bir bakış açısı altında, değişik yerlerde yapılan çalışmaların incelenmesi sonucunda sorunların belli kalıplarda benzerlikler gösterdiği anlaşılmaktadır. Dünyada gerçekleştirilmiş tünel açma faaliyetlerinin birçoğu incelenerek değerlendirmesi yapılmıştır. Kazı işlemine bağlı olarak makinenin sebep olduğu aksaklıklar, delme-patlatma işlemine bağlı sorunlar, istihkakla alakalı sorunlar şeklinde ortaya çıkabilmektedir. Karşılaşılan en önemli sorunlar kaya boşalmaları(göçük), tahkimat, taban kabarması, yüzey tasmanları, su geliri, aşın sökülme, gaz çıkışı, kesici uçlara ve makineye bağlı sorunlar, yatay-düşey deformasyonlar, vibrasyon gibi ortaya çıkmaktadır. Bahsedilen sorunların tümü incelenerek bunların ne gibi önlemlerle bertaraf edileceği anlatılmaktadır. Sorunların ve çözümlerin birarada incelenilmesiyle somut sonuçlara ulaşıldığı görülmektedir. Tünel kazısında, ortam şartlarına bağlı olarak gereken ne ise yapıldığı taktirde sorunların büyümeden yokedilebileceği görülmektedir.

The main purpose of this research, is to observe the development of tunneling and tunnel machines all over the world, to analyze the problems that occurs during the tunnel excavations and to perform the solutions for those problems. Firstly, the historical development of tunneling has been mentioned. The earliest utility tunnels were constructed more than 3000 years ago by the Babylonians, Aztecs and Incas in the search for precious metals and by the peoples of India, Persia and Egypt. Until about the nineteenth century tunnels in hard rock were excavated by fire at the face, then spraying water on the hot surface. Progress amounted to about 1 m. per week. In the early days the drill steel was driven by sledge hammer and penetration rates of about 1 m/h. were the best that could be achieved. Improved drill bits led to much more efficient drilling and blasting, and opened the door for invention of the rockbolt. Technology improved dramatically from the mid 1900's. Jacklegs were replaced by Jumbos with as many as six booms. Heavier and more powerful equipment allowed drilling of larger (35 and 45 mm.) blastholes. Pneumatic ANFO loading equipment was mounted on the Jumbo, reducing by about twenty percent the time required to charge the blastholes of a tunnel round and cutting the cost of explosives to about one-half. Hydraulic drill introduced in the mid 1970's nearly doubled the drilling rate and reduced the noise and mist levels dramatically. The observation of the big tunnel excavation activities was developed with rail roads. The first most important rail road tunnel is Mont Cenis tunnel. This tunnel has been excavated with hand but after it has been used pneumatic equipment system. After years Washington Metro, Galata-Pera tunnels, Simplon-1 tunnel, Chicago, Philadelphia, Hamburg, Buenos Aires, Madrid, Barcelona Metros were opened. The biggest one project that was developed with Europe is the Manş tunnel. And this project was completed at 1993. In 1993, the pieces of metro network system that was cause to work is approximately 150 all over the world. In our country, İstanbul and Ankara Metro construction works continues for the their future underground network system. -X- After, TBM, roadheader, mobile miner and impact hammer were mentioned. In variety rock conditions, TBM properties is different. There is a special model machine in every rock condition. And this point is very important. Because, if you can select appropriate machine for rock conditions, you can obtain the good cost and this is the real success. For this reason, the parameters that will be effect at TBM selection were explained. In the use of TBM's most advantage and disadvantage are available. During the TBM selection, tunnel length and rock conditions are most important. Roadheaders work short tunnels with small costs. This is the big advantage for tunnel excavations. And it works different tunnel diameters. This is another big advantage. Roadheader machines that excavate only part of the face at any one time are much more maneuverable. Although not capable of penetrating massive or high-strength rock (uniaxial compressive strength should be less than about 60 MPa, and the abrasivity should be low), they can be introduced easily in to the tunnel for limited lengths of driveage at locations where the rocks are suitable, and can be withdrawn to a safe distance to allow blasting. The modern machines that are being produce by means of Alpine Westfalia were explained with all technical datas. From other side mobile miner and impact hammer were explained with all technical properties, excavations costs and performances. In part three, the tunnels length that were driven by Karayolları Genel Müdürlüğü and Devlet Su İşleri were explained. On the other hand, the tunnels length that were driven by the machines that were produced between the years of 1967-1980 were explained. Shortly, total tunnel lengths in the world were explained. Besides, tunnel costs were researched. In part four, tunnel excavation process and supporting were clarified. In tunnels, excavation makes with either drill-blast method or any kind of excavate machines. Beside, the observations that were made in İstanbul Metro were explained. Boring is less disruptive than blasting and produces a more stable that tunnel requiring less support. İn our days full face boring machines can cut economically through most types of ground. However, they are expensive to buy and to transport. Blasting is usually cheaper than boring if ground conditions change often along the route. Unexpectedly hard or soft rock, or higher than expected levels of ground stress, can delay the work and damage the machine. There are three major reasons for ground support: to maintain stable conditions above and around the tunnel, to provide safe working conditions and steady progress during construction, and to provide a liner with long- term performance characteristics of water tightness and stability, the purpose of primary support, installed by the contractor as required, is to ensure safety during construction and stability above the tunnel. Secondary support, installed at the discretion of the tunnel engineer, consists of extra materials to augment safety or to improve hydraulic characteristics. Ground support that lasts only for the period of construction is provided by the shield of a boring machine or by an independently mounted shield. Rockbolts are used alone when the rock consists of large, durable blocks, but are better -XI- used in combination with shotcrete, wire mesh and steel ribs, straps.or crown plates when the rock is weak or broken. The NATM uses reinforcement and coating materials in proportions that are adjusted to suit the ground. Professor L.V. Robcewicz coined the name New Austrian Tunneling Method (NATM), in contrast to the old Austrian method which employed mainly timber. Close monitoring of convergences and liner pressures, an essential part of the NATM, allows support to be added progressively when and where needed. The and result is an economical (although slow to install) system that minimizes both ground displacements and support quantities and gives excellent control in badly crushed, squeezing and swelling rock, or even soil. The best rock (strength more than 4 times the ground stress) needs either no support, or rock bolts in the crown only. Progressively deteriorating conditions require an initial "first aid" coating of shotcrete, 20 to 40 mm. Thick, that helps the rock arch and support itself, followed if necessary by bolting and additional layers of shotcrete with wire mesh between each layer, (now often replaced by steel fiber reinforcement). Near faults and zones of potential ground squeeze, the shotcrete layers are further reinforced by flexible light weight steel ribs with a U-shopped cross section. These may be constructed from overlapping telescopic segments to accommodate rock squeeze without becoming over stressed, and are pulled tight against the rock surface by rock bolts. They are widely spaced when only nominal support is needed, but are as close as 0,5 to 1,0 m. where extremes of ground squeeze are expected. Steel ribs are nowadays often replaced by lattice girders fabricated from reinforcing steel. These are lighter in weight and easier to at attach to the rock. When shotcreted, they form a reinforced concrete beam. The NATM was introduced in Austria, France, Germany, Switzerland, and Italy and its use rapidly spread worldwide. One of the earliest applications was in the Frankfurt underground railway tunnel, which was driven in 1969 through interlaminated clay marl, chalk and sandstone. Cover amounted to only 6,2 m. where the line passed the historic Roemer building. The support used in the NATM is flexible in two senses. It is mechanically flexible and can deform to accommodate rock squeeze while continuing to act as a coherent membrane. It is versatile in that it can be adjusted to match support requirements that vary from place to place. The more traditional alternative of installing a single support system throughout a tunnel requires a design to resist to worst, not just the average, anticipated ground conditions. The single system alternative is simple and requires less skill, control, inspection, monitoring and testing. It is usually best for short tunnels of small diameter when ground conditions are well known and uniform. The NATM is nearly always best for longer and longer tunnels in conditions of lesser known and variable ground. Precast liners are, however, much quicker to install, and are ideal for rapid tunneling through uniform ground. Crown plates can be a very effective means of support in bored -xu- tunnels. Reinforced shotcrete is strong, resilient, and durable. During recent years, additives such as microsilica and steel fiber reinforcement and steel fiber reinforcement have made possible high strength of shotcrete to replace the older, more labor intensive method of shotcrete reinforced by welded wire mech. Wet mix shotcrete now appears superior to the dry mix process. Besides empirical and semiempirical methods were explained shortly. Purely empirical methods are those that predict tunnel support requirements from a knowledge of ground conditions, using a preestablished correlation. Semiempirical methods predict rock loads empirically as an intermediate step, and then go from rock loads to support requirements via a simple theoretical model of support behavior. Empirical Methods; - Deere's Method - RSR System - RMR System - Size-Strength System - Q System Semiempirical Methods; - Rock Load Method - Terzaghi's Method A1, A2, A3 type of supportation methods were explained with details. If the subsidence occurs, injection process application. There are a lot of injection process. These are touch injection, consolidation injection i.e. Drainage process is also a stabilization process. Leakage of water can be hazardous particularly when under pressure. High capacity pumping equipment is needed to prevent flooding when inflows are substantial, such as in karstic limestone. Hot water at depth can be more of a problem than cold water. Besides, natural gases are found in pockets in some rock formations. Gases such as methane, when they seep into a tunnel, present a serious hazard because of their toxicity and particularly their explosion potential. Tunnels can be observe regularly by means of inclinometers, convergence measurements, crack gauges, multiple extensometers, vibrating wire strain gauges, pressure cells, load cells, piezometers, settlement gauges and leveling monuments. If you observe the problems right time, it can be solves shortest time and minimum damage and cost. Tunnel engineering can examine in four parts. These are; -Economical part, -Administrative part, -Theoretical part, -Practical part. All of these parts are important during the tunneling process. Economical part is connected directly with the finance. In administrative part, all persons -XU1- who works for the tunneling process must be professional on their areas. Every person is a unit that forms a successful team. In tunneling process, theoretical approaches must make a great care. This part of process is more important for future project. Practical part is a application of theory, but in practical applications, it has been observed many problems during the work. Different problems being formed during project applications are different each other. Some problems are depends on the excavation, some of machines, some of stabilizations, some of ventilation, some of drilling- blasting. All problems should examine with care. If you make right work in right time, with right machines and persons, problems decreases directly.