Yeraltı raylı sistem inşaatlarındaki geoteknik uygulamalar: Halkalı- yeni havalimanı metro hattı örneği
Geotechnical applications in underground rail system construction: The case of Halkalı-Istanbul Airport subway line
Yazar: RABİA KELEŞ
Danışman: DOÇ. DR. İSA VURAL
Sakarya Uygulamalı Bilimler Üniversitesi / Lisansüstü Eğitim Enstitüsü / İnşaat Mühendisliği Ana Bilim Dalı
Derece: Yüksek Lisans, 2022
Konu: İnşaat Mühendisliği = Civil Engineering
Dizin: Raylı sistemler = Railway systems ; Tünel açma makineleri = Tunnel boring machinery ; Yeni Avusturya tünel inşa yöntemi = New Austrian tunneling method ; Yer altı yapıları = Underground structures

Özet:
Bu tez kapsamında örnek olarak Halkalı – Yeni Havalimanı hattının imalatı öncesinde yapılan jeolojik çalışmalar ve imalatı sırasındaki geoteknik uygulamalara ait detaylar paylaşılarak yeraltı raylı sistem imalatlarında karşılaşılan problem verileri incelenecektir.
Jeolojik incelemesi dört kısımda yapılan yaklaşık 30 km uzunluğundaki metro hattında toplam 9588,5 m uzunluğunda 198 adet karotlu araştırma sondaj yapılmıştır. Bu sondajlardan 1006 adet zemin, 1230 adet kaya numunesi elde edilerek üzerlerinde yapılan laboratuvar deneyleri ve sondajlar sırasında gerçekleştirilen arazin deneyleri sonuçlardan hareketle hattın jeolojik kesiti oluşturulmuştur. Oluşturulan jeolojik kesitin yeterli gelmediği fay zonlarının, karstik boşlukların bulunduğu problemli bölgelerde doğru veriler elde edebilmek amacıyla üç farklı konumda Çoklu Elektrotlu Elektrik Rezistivite Tomografi yöntemi kullanılarak yapılan jeofizik çalışmalar ile 2 boyutlu yeraltı özdirenç ters çözüm kesitleri elde edilmiştir. Bu kesitler ile sondaj logları ile elde edilen kesitler karşılaştırılmıştır.
Halkalı-Yeni Havalimanı metro hattı 31,3×2 km ana hat, 1,8×2 km depo bağlantı hattı olmak üzere toplam 66,2 km uzunluğundaki yeraltı tünellerinden oluşmaktadır. Hatta 7 adet metro istasyonu, 1 adet YHT (Yüksek Hızlı Tren) istasyonu, 11 adet makas yapısı, 8 adet servis istasyonu, 2 adet acil kaçış şaftı, 12 adet inşaat şaftı ve 106 adet ara geçiş (Cross-Passage) tüneli bulunmaktadır. Projedeki Tünel Açma Makinesi (TBM) kullanılan tünellerinin uzunluğu yaklaşık 55,7 km, Yeni Avusturya Tünel Açma Metodu (NATM) uygulanan tünellerin toplam uzunluğu ise yaklaşık 15,8 km'dir. Kazısı TBM ile açılacak tünellerin kesitleri tam dairesel, istasyon, makas, bağlantı ve ara geçiş gibi tüneller ile kazısı NATM ile planlanan diğer tünel kısımları ise genellikle at nalı şeklinde ancak değişik tip, çap ve kesitlere sahip olacaktır.

Abstract:
This thesis aims to provide a template for underground rail system manufacturing by sharing details of the geological work done prior to the construction of the Halkalı-İstanbul Airport and the geotechnical implications during its construction.
A total of 198 core research drillings with a total length of 9588.5 m were made on the approximately 30 km long metro line, whose geological investigation was carried out in four parts. The geological section of the line was formed based on the laboratory tests performed on 1006 soil and 1230 rock samples obtained from these drillings and the results obtained from the field tests carried out during the drillings. Two-dimensional subsurface resistivity inversion sections were obtained by geophysical studies using the Multiple Electrode Electrical Resistivity Tomography method in three different locations in order to obtain accurate data in problem areas where the fault zones and karst voids are not sufficient. These sections were compared with the sections obtained by drilling logs.
Halkalı-Yeni Havalimanı metro line consists of underground tunnels with a total length of 66.2 km, of which 31.3×2 km is the main line and 1.8×2 km is the warehouse connection line. In the line, there are 1 YHT (High Speed Train) station and 7 metro stations, 11 truss structures, 8 service stations, 2 emergency escape shafts, 12 construction shafts and 106 Cross-Passage tunnels. The length of the tunnels using the Tunnel Boring Machine (TBM) in the project is approximately 55.7 km, and the total length of the tunnels using the New Austrian Tunneling Method (NATM) is approximately 15.8 km. The sections of the tunnels to be excavated with TBM are fully circular and the cross-section of the station and switch and connection and intermediate tunnels, whose excavation is planned with NATM, will generally be horseshoe-shaped and will have different types and dimensions.
In the project, NATM is applied in many locations and sections with different usage purposes, such as truss tunnels, connection tunnels, stair tunnels, mezzanine tunnels, elevator tunnels, platform tunnels, approach tunnels, intermediate transition tunnels and electric-machine shaft tunnels.
In this project, the areas formed by the 7 stations (Arnavutköy 1, Arnavutköy 2, Fenertepe, Kayaşehir, Olympicköy, Halkalı Stadium, Halkalı) form the platform tunnels. At the stations, there are connection tunnels to provide the transition between the lines, elevator and stair tunnels to bring the passengers to the surface, intermediate tunnels that serve as a landing at the stations consisting of two floors, and electrical-machine shaft tunnels. Electric-machine shaft tunnels are located at stations outside the passenger area. Transition from shaft to line tunnels is provided by approach tunnels. Temporary fortifications in NATM tunnels consist of approximately 1 m long shoring. Shotcrete (C20 or C25), steel mesh (B500C), lattice
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beam (Reinforcement: B420C), 4 meters or 6 meters long rock bolts, the number of which differs according to the soil type, are used in the shoring. After the temporary support fabrication is completed in the tunnel, reflectors are placed on the shoring, 3 (The number increases in large sections such as platform and truss tunnels) in ring wool, at 10 meters intervals. The purpose of the reflectors is to follow the deformations in the tunnel at varying time intervals depending on the deformations until the permanent coating is done. Before the reinforced concrete permanent coating is applied, insulation is applied inside the tunnel. NATM tunnels are inverted anodes, curves and truss tunnels as 6-metre lanes and on the alignment, it is produced as 12-meter anodes. The concreting process of the slabs, where the piers are built and the reinforcements are placed, is carried out by means of 6 m or 12 m long steel molds specially manufactured for tunnel sections. In order to provide watertightness, waterstop tapes are used in the belt invert junction areas and the junction areas of the anodes.
The production of approximately 60 km long TBM tunnels will be carried out with 6 different TBMs, and the process is managed by dividing the line into four phases. TBM produces one ring and one excavation per hour in stable conditions. This means that the machine is fed hourly with the injection mortar required for a minimum of 6 segment stones and a ring. The length of this route, which feeds the TBM, where various productions continue on the line and a single vehicle can move forward or backward without any maneuvering space, is determined as a result of the optimization of the time and cost calculation of the disassembly and installation process of the TBM. The suitability of the location and areas of the TBM entrance-exit structures, the total length of the line, and the number of machines to be used can be counted among other factors. TBM carries out the excavation by means of cutting blades and cutting discs located in the cutter head. The excavated ground is transferred to the excavation area with the help of the cavities in the cutter head. The power of the advancement rollers is transferred to the excavated material (waste) through the pressure chamber, preventing uncontrolled leakage of the ground from the mirror to the excavation area EPB TBM (Earth Pressure Balance Tunnel Boring Machine) keeps the ground collapses and swellings under pressure by converting the space into a closed volume in order to control the water pressure. The purpose is for the rust to fill the cutter head chamber (excavation area) and support the entire surface. The lining of the tunnel consists of prefabricated concrete segments. In the shield area, under atmospheric pressure, behind the pressure wall, the segment erector is lifted by the vacuum system that can rotate 360º, and the segment is brought to the position where it will be mounted, and the assembly is carried out. The outer diameter of the segments used in the project is 6.3 m and the inner diameter is 5.7 m. The segments are 1.5 m long and 30 cm thick. A ring is composed of 6 segments in 5+1 shape. These segments are named A, B, C, D, E, and F. 'D' is the segment with the largest dimension and 'A' is the key segment. Thanks to the millimeter differences between the segments and the various combinations created with the segments, the TBM is guided using push rollers with a horizontal movement area of 1.80 m on the machine. The creation of a ring starts with the 'D' segment and the 'A' lock segment is placed last. The union of the two rings is provided with the help of pins, which have a total of 16 in the segments. With the TBM, there are support elements that progress from the entrance structure to the exit structure. These can be listed as 34 500 volt MV (Medium Voltage) cable, conveyor belt system that provides the transfer of rust from inside the tunnel, drainage line, machine cooling water and tunnel ventilation fan.
The cut-cover method was used in some of the switch structures, service stations, construction shafts and concourse areas forming the passenger entry-exit zones at the stations. This method has the principle of taking timbering measures before excavation in the area to be excavated. First, excavation is taken from the land surface to the top of the pile. The reinforcements prepared in the field are placed in the drilling well with the help of a tower crane, paying attention to the concrete cover. This can be done in one or several stages, depending on the pile size. Concreting of the piles is done by using pile-length tremie pipes in order to minimize manufacturing errors and to pour the concrete without free fall. After the production of the remaining piles is completed, it is ensured that the piles at the same level work together with the help of cap beams. Waler beams are produced with gradual excavation. Before proceeding to the next stage excavation, one of the strut or anchor applications is preferred in order to meet the lateral loads.