İstanbul Gayrettepe- yeni havalimanı tünel tahkimat sisteminin sayısal yöntemlerle incelenmesi
Investigation of Istanbul Gayrettepe-new airport tunnel fortification system by numerical methods
Yazar: MUHAMMET SERHAT TOKTAŞ
Danışman: DOÇ. DR. HAKAN TUNÇDEMİR
İstanbul Teknik Üniversitesi / Lisansüstü Eğitim Enstitüsü / Maden Mühendisliği Ana Bilim Dalı / Maden Mühendisliği Bilim Dalı
Derece: Yüksek Lisans, 2021
Konu: Maden Mühendisliği ve Madencilik = Mining Engineering and Mining ; Mühendislik Bilimleri = Engineering Sciences

Özet:
Şehirleşmenin günden güne artması ile birlikte büyükşehirlerde trafik sıkışıklığı sorunu artmıştır. Bu gibi ulaşım sorunlarını çözmek amacıyla ülkemizde son yıllarda çok sayıda metro tüneli hattı açılmıştır. Nüfus yoğunluğu çok yoğun olan illerde hızlı toplu taşıma araçlarına ihtiyaç duyulması sebebiyle, yeraltı tünel uygulamaları vasıtasıyla ulaşım ağı sorunu çözülmeye çalışılmıştır. Bu amaçla açılan İstanbul Gayrettepe-Yeni Havalimanı metro hattının açılması ile İstanbul Havalimanı'na ulaşım sorunu büyük ölçüde çözülecektir. 
Yapılan geoteknik çalışmalarla tünelin geçiş güzergahı boyunca bulunan jeolojik formasyonların sırasıyla, Trakya, Kartal, Aydos ve Dolayoba formasyonları olduğu tespit edilmiştir. Bu formasyonlar geoteknik çalışma sıralamasına göre genel olarak zayıf ve orta kaya sınıfındadırlar. İstanbul Yeni Havalimanı metro tüneli, TBM (Tam Cephe Tünel Açma Makinesi) ve NATM (Yeni Avusturya Tünel Açma Yöntemi) kullanılarak kazılmıştır. NATM ile tünel kazısında ana destekleme sistemleri kafes iksalar, püskürtme beton ve bulonlardır. 
Bu çalışmanın amacı, NATM ile açılan metro yapım aşamalarının ve açıklık geometrisinin formasyonun jeomekanik özelliklerine göre incelenmesi ve destekleme sistemlerinin analitik ve sayısal yöntemlerle irdelenmesidir. Çalışmada tünelciliğin tarihsel gelişimi, kaya sınıflama sistemleri ve kullanılan diğer yöntemler de incelenmiştir. 
Tünelcilik çalışamalarında tünelin açılıcağı ortam şartlarının zorluğu ve formasyonlardan kaynaklanan beklenmeyen durumlar oluşmaktadır. Bunun yanı sıra özellikle şehir içi tünel yapımında şehir üst yapısının durumuda etkili bir parametredir. Bu nedenle tez çalışmasında tahkimat sistemi incelenirken ampirik ve sayısal modelleme teknikleri kullanılmıştır.
Tezde değerlendirilmesi yapılan 3 ayrı bölge bulunmaktadır, bu bölgeler NATM ile kazılmıştır. Aynı özellikleri gösterdiği düşünülen 3 homojen bölge RMR ve NATM'ye göre sınıflandırılmış ve bu bilgiler baz alınarak bir tahkimat sistemi oluşturulmuştur. Oluşturulan tahkimat sistemi RS2 2019 programı ile modellenmiştir. Yapılan analiz sonuçları değerlendirilerek yorumlanmıştır.

Abstract:
Increasing in urbanization day by day, the traffic jam problem has risen up in metropolitan cities. In order to solve these kind of transportation problems, many metro tunnel lines have been driven in our country recent years. Due to the necessity for fast public transportation in provinces with high population density, the problem of transportation network has been a solution with tunnel applications. Opening of the Istanbul-Gayrettepe New Airport metro line, problem of transportation to Istanbul Airport will be solved to a great extent. 
According to geotechnical analysis of the tunnel route, the geological formations on the tunnel zone are Trakya, Kartal, Aydos, and Dolayoba formations, respectively. These formations are considered as weak and medium strength rocks due to the geotechnical investigation. The excavation of the Istanbul New Airport metro tunnel was performed by TBM (Tunnel Boring Machine) and NATM (New Austrian Tunneling Method). Main supporting systems in tunnel excavation are truss beams, shotcrete, and bolts. 
In tunneling works, unexpected situations arise due to the difficulty of the environmental conditions in which tunnel will be opened and formations. In addition, state of the city superstructure is an effective parameter, especially in urban tunnel construction. For this reason, empirical and numerical modeling techniques were used while examining fortification system in the thesis.
In this study, primarily rock classification systems are explained and then failure criteria are introduced. Then, the geological-geotechnical studies carried out in the M2 tunnel located in the Km 4+231 region on the Gayrettepe - Istanbul New Airport Metro Line route, the M5 tunnel in the Km 21+405 region, and the M9 tunnel in the Km:33+937-34+117 range are given. . Rock structure on the Gayrettepe – Istanbul New Airport (GYH) metro line has been introduced.
Aim of this study is to examine subway construction stages and support systems of the opening geometry according to the engineering features of the formation with analytical and numerical methods. In this study, historical development of tunneling and other methods used in tunneling are examined in detail. There are 3 regions evaluated in the thesis. These regions were excavated by the New Austrian Tunneling Method. In this study, 3 homogeneous regions were classified according to RMR and NATM. A support system was created based on these rock classifications. The fortification system created was modeled with the RS2 2019 program. The results of the analyzes were evaluated and interpreted.
A fortification system was created by evaluating the scores made according to the RMR and NATM classification methods. The reinforcement elements in the M2 tunnel are steel mesh Q221, shotcrete and rock bolts. The reinforcement elements in the M5 tunnel are steel mesh Q221, shotcrete and rock bolts. The reinforcement elements in the M9 tunnel are shotcrete and steel mesh Q221. These fortification systems were introduced in the RS2 2019 program and numerical analysis and numerical analysis of the tunnels were made. 
RS2 (Formerly Phase 2) is a powerful 2D finite element program for soil and rock applications.  RS2 can be used for a wide variety of engineering projects, including excavation design, slope stability, groundwater seepage, probability analysis, consolidation and dynamic analysis capabilities. Complex, multi-stage models can be easily created and quickly analyzed in the RS2 program
M2 zone is entirely sandstone, siltstone, claystonewhich is formed of the Thrace formation. In the M2 region, there are 4 different formations: lightly fragmented new rock (W1-W2), high-medium fragmented Rock (W3-W4), fully fragmented rock (W5), artificial fill (Yd). While evaluating  numerical analysis in RS2 2019, with and without support, sigma 1 values, sigma 3 values, sigma z values and deformation values were examined separately while modeling.Formation of the geotechnical model of the M2 tunnel in the RS 2 program with support took place in 7 stages, and the formation of the geotechnical model without support took place in 4 stages. Observation reading points were created in order to numerically examine the maximum compressive stresses, displacement values and safety factor values of support system in the models operated. Visuals of the maximum sigma and displacement values at the observation reading points were given and interpreted after analysis.
There are two ground formations in the M5 region. These soils are hard sandy clay (Tda), hard clay intermediate sand-sandstone (Ct). While carrying out the support analysis of the M5 tunnel, sigma 1, sigma 3, sigma z and and displacement values were taken into account and interpreted according to the results in the tunnel section supported and tunnel section unsupported models established in the RS 2019 program. Formation of  geotechnical model of  M5 tunnel in RS 2 program took place in 7 stages, and formation of geotechnical model without support took place in 4 stages. In models established in RS 2 2019 program, maximum sigma and deformation values at observation reading points were analyzed and interpreted.
In region where M9 tunnel is located, there are two rock formations: very solid-hard clay layer (Tda) and hard clay-claystone (Tda). While evaluating the numerical analysis, sigma 1 values, sigma 3 values, sigma z values and deformation values with and without support were taken into consideration. In the RS2 2019 program, sigma and deformation values of the models installed in the M9 tunnel with and without support were analyzed and interpreted.
In this thesis,  critical sections of  M2, M5 and M9 tunnels, which were opened using  New Austrian Tunneling Method, were examined in the tunnel construction of Istanbul Gayrettepe New Airport. Considering formation excavated in tunnels, examination of stress and displacement relationship gives important information about stability of  tunnel before, during and after tunnel excavation.
In the numerical modeling studies performed, the points where the stress orientation and safety coefficient values are less than one were determined during the tunnel excavation. In this way, the areas that need special attention while excavating have been determined. The points found are in the classification of the region that is subjected to the most difficulty in the analysis in the RS2 2019 program. Since rock mass properties and stress conditions are frequently changing parameters in tunnel excavations, early attention should be paid to the support design of these points.
Studies in this thesis style should be considered as a preliminary project in underground project studies such as mines and tunnels. One of the basic principles of NATM, situations that will occur during the excavation phase should be examined on-site and necessary fortification changes should be made on site.