Metro Tünelleri Üstyapı Etkileşimleri

Abstract

Sunulan çalışmada, yapımı devam eden metro tünelleri inşaatının üstyapıya olan etkileri ve üstyapıda meydana gelebilecek olan hasarların hasar seviyeleri düzeylerinin incelenmesi amaçlanmıştır. Çalışmaya metro tünellerinin kazı aşamaları açıklanarak başlanmıştır. Metro tüneli kazı yöntemlerinin seçimi açıklanmıştır. Metro tünellerinin seçilen kazı yöntemlerine göre oluşturulan tünel tipleri açıklanmıştır, tünel tipleri için farklı zemin koşulları ve üstyapı koşulları altında hesaplar sonucu ortaya konan tünel kazı destek tipleri ayrıntılı anlatılmıştır. Metro tüneli kazı aşamaları kazı yöntemine göre sırasıyla açıklanmıştır. Metro tüneli yapımı nedeniyle zemin hareketleri, zemin-tünel, zemin-yapı, tünel-yapı etkileşimleri incelenmeye, arasındaki etkileşimler anlatılmaya çalışılmıştır.Metro tüneli-zemin etkileşimi teorik olarak anlatılmıştır. Zeminde ve bina temel tabanında meydana gelen düşey oturma nedenleri, düşey oturmaların nasıl oluştuğu açıklanmış, oturma metodolojisi ayrıntılı olarak anlatılmıştır. Metro tüneli-zemin ilişkisi zemin-üstyapı ilişkisi, genel olarak metro-tüneli üstyapı ilişkilerinde oluşabilecek olan deformasyon nedenleri anlatılmıştır. Yapılarda hasar tespiti açıklanmış, hasar tespiti tahminleri için kullanılan değerlendirmeler, metotlar ayrıntılı olarak açıklanmıştır. Metro-tüneli üstyapı etkileşiminde sonlu elemanlar yöntemi kullanıldığı belirtilmiş, analizlerin gerçekleştirilmiş olduğu sonlu elemanlar yöntemini kullanan Plaxis programı anlatılmıştır. Zemin, tünel ve temsili üstyapı modellemeleri Plaxis programı kullanılarak yapılmıştır. Modellerin oluşturulma aşamaları anlatılmış, programdan ara yüzler gösterilmiştir. Metro tüneli-üstyapı etkileşmini açıklamak için, farklı tünel tipleri, farklı zemin tabakaları ve farklı özellikteki binalar seçilmiştir. Her bir farklı durum için Plaxis programı ile analizler gerçekleştirilmiştir. Plaxis programı ile analizler sonucu kesit tesir diyagramları elde edilmiştir. Analizler sonucu yapıda ise açısal distorsiyon, yatay ve düşey deformasyon değerleri elde edilmiştir. Gerçekleştirilen analizlerdeki tünellerin dizaynının depreme dayanıklı olarak tasarlandıkları düşünülmüştür. Analizler sonucu yapılar için tahmin edilen deformasyon değerleri kullanılarak hasar seviyeleri tahmin edilmeye çalışılmıştır. Hasar seviyelerinin tahmini için geliştirilen üç aşamalı değerlendirme yöntemi kullanılmıştır. Üç Aşamalı Hasar Değerlendirme Yöntemi Mair tarafından geliştirilmiş bir metottur [1]. Üç Aşamalı Değerlendirme Yönteminde Plaxis programı ile yapılan analizler sonucu elde edilen deformasyon değerleri ile yapıda meydana gelebilecek hasar durumu aşama aşama değerlendirilerek tahmin edilir. İlk aşama değerlendirmede yapıdaki oturma değeri (düşey deformasyon) 10 mm’den küçük ve açısal distorsiyon 1/500 değerinden küçükse yapılardaki hasar seviyesi ihmal edilebilir olarak tahmin edilir ve ilk aşama değerlendirme tamamlanmış olur. Eğer yapıdaki oturma 10 mm’den büyükse ya da açısal distorsiyon 1/500 değerinden büyükse ikinci aşama değerlendirmeye geçilir ve hasar seviyesinin tahmini Mair tarafından belirlenen çizelgeye göre yapılmaya devam eder [1]. Yapılan analizlerin sonuçlarına göre binaların temel seviyesinde hesaplanan maksimum düşey deplasman değerleri ve maksimum açısal dönme değerleri izin verilen değerlerin altında olup olmadığı belirtilmiştir. Analizler sonucu üstyapıda beklenen düşey deplasman ve açısal dönme değerleri betonarme binalar için izin verilen değerleri 1/500, Bowles’a göre değerlendirilip hasar seviyeleri belirlenmiştir [2]. Böylelikle üstyapıda beklenen hasar durumları ortaya konmaya çalışılmıştır.

As the technology grew and became available to public for cheap, the traffic made its way to the top of the list of main urban problems in big cities. Especially in Istanbul where the city grew its boundaries too much and population grew over tens of millions. The traffic is huge problem, millions of people spend most of their time on the way so as to go their work or house. Transportation by subway became a faster solution. So the construction of subway tunnels rapidly became one of the top priorities of metropolitan cities. The purpose of this study is to investigate the effects of ongoing subway tunnel construction on superstructure and calculating the damage that will be done to the superstructure. Especially in İstanbul there are so many buildings that are made of masonry, concrete and timber exist. Most of the buildins are old and some of them have residual damage from prior earthquakes or poor material or engineering qualities. Some of the buildings do not have the adequate stability. This study starts by explaining the stages of tunnel excavation. The construction types of subway tunnel is explained. Also the process of choosing subway tunnel excavation method is explained. After explaining the construction types, the types of tunnel is explained. Tunnel types depending on the choosen excavation methods are listed and tunnel excavation support types, depending on the tunnel type, different soil conditions and superstructure conditions, are explained in detail. Not only tunnel types are explained, but also the support system of tunnels are explained. The types of support systems are explained in a detailed way with photos. The subject of this study is to investigate the effects of tunnel excavation to the superstructure. The effects are in relationship with soil type, tunnel geometry, superstructures and ground water. The relation starts with the excavation. The tunnel excavation method change with the tunnel type. Excavation stages of subway tunnels are stated according to excavation method. It is remarked that there are different excavation stages with the different types of tunnels. It changes according to the geometry of the tunnel. The interaction between soil-tunnel, soil-buildings and tunnel-buildings are investigated caused by construction of the tunnel. Before construction starts, all buildings which are near places in the line of the tunnel are investigated.The buildings are investigated so as to know their structural informations and damage situation. If there is building which has small damage, the building will be protected more than others. Not only building protection is important, but also it is important to make observations adequately. The observations are made in tunnel and at site, buildings. The main problem in subway tunnel-superstructure is that the ground loss. The ground loss defined like that the excavation area which is more than the tunnel area. The ground loss is explained by it parameters.When the excavation starts, there will be a ground loss. Ground loss changes by conditions. The tunnel depth, the soil type and the superstructure conditions. The ground loss is an important topic because it causes the settlement in soil. So, the settlements effect building badly. The settlements effect buildings footing. The settlement in soil causes the deformation in the building’s footings. The deformations that are caused by settlements are angular distorsion and vertical displacement. In this study different types of soil be modelled and the analyses have done. For different type of tunnel (different geometry), different types of soil and different buildings models are performed with Plaxis programme. The Plaxis programme is also explained in this study. Plaxis programme works with the finite element analyses method. In Plaxis programme different type of tunnel, soil and building analysed together with different combinations.The models have analysed in Plaxis programme. The stability of tunnel is controlled. Plaxis programme gives the deformation values, after the analyses. The programme give deformation values not only for the tunnel but also for the superstructures footing. So as to have these values, the geometry of superstructure and the mean value of one story distrubuted load (it is 20 kN /m² for this study) are needed.The informations are input datas and the output datas are the deformations value. Deformations on superstructure caused by different superstructure and different soil conditions are calculated and parametric studies are made. Damages and damage grades during construction stages are evaluated. The Mair’s Three Step Method is being used for predicting the damage level . The method consist of three steps. In the first step evaluation, if the angular distortion is less than 1/500 and the settlement is less than 10 mm, the building damage level is estimated like negligiable [1]. Analyses are made with the help of computer program Plaxis. Vertical displacement, lateral unit deformation and angular rotation amounts are calculated depending on the analysis results. In every analyse it is thought that the tunnel design is convenient for the earthquake situations. Lateral unit deformation and angular rotation amounts calculated are interpreted according to the graphic by Boscardin & Cording (1989) and damage grades are specified [3]. Results are interpreted according to the graphics. It is specified if the vertical displacement and maximum angular rotation values on the foundation level of the building calculated with the analysis are within allowed limits specified by (1/500, Bowles, 1988) [2]. With this, expected damage conditions on superstructure is calculated. Lateral unit deformation and angular rotation amounts calculated with Plaxis are effected on the model building on superstructure. Subway tunnel-superstructure interactions are studied extensively, possible deformations are determined and acceptable limits on concrete structures according to (1/500, Bowles, 1988) are evaluated and damage limits are determined [2]. The effects of subway tunnels to the superstructures is evaluated. Not only the calculations are important, but also it is important to continue taking field surveys. Field surveys can be done when the construction is going. The deformations can be observed by the targets which can be placed into tunnels and structures, so if there is any change it would be easy to observe when the construction is being made. The subway tunnel is one of the most important solutions for the traffic problem urban areas. The traffic is problem for working people. Working people spend most of their time by working. For this reason they do not want to lose their time by going to work and also going to their homes from work. For an example, İstanbul always has traffic in such places. Especially if it is the Friday night, the traffic is getting more and more. The trafic problem can change by days increasingly. For a different view; if the weather is rainy, the traffic becomes more crowded and consequently you will spend more time on the road. Therefore the subway transportation is one of the most convenient solution for the traffic problem. Transportation by subway has been used in the developed countries since the beginnig of the 1900’s. In our country, the subway transportation has been prefered in big cities so as to make better traffic conditions. The subway routes mostly through under the buildings. Though it is important to know about the buildings’ structural properties. Before the subway tunnel construction, an investigation must have done for the buildings, road, bridges and other structure’s properties. The Building Audit Companies make the investigation and prepare the report of the structures in the subway route area. The report consists of buildings’ material type, age, number of the stories, damage situation. It is important to know these informations before tunnel construction and to make provisions. Field surveys should be done before and during the tunnel construction, and the reports of deformation measurements must be prepared so as to track the changes. It is important to continue taking field surveys, when the construction is going. The deformations can be observed so if there is any change it would be easy to track changes, to control the deformations so as to take precautions.