Şev güvenliğinin belirlenmesine yönelik zemin etütleri, zemin modelleme ve depremli durum şev stabilitesi analizleri içeren bir vaka analizi
A case study including soil investigation, geotechnical modelling and seismic slope stability analyses for determination of the safety of a slope
Yazar: CANDENİZ DOLU
Danışman: PROF. DR. HÜSEYİN YILDIRIM
İstanbul Teknik Üniversitesi / Fen Bilimleri Enstitüsü / İnşaat Mühendisliği Ana Bilim Dalı / Zemin Mekaniği ve Geoteknik Mühendisliği Bilim Dalı
Derece: Yüksek Lisans, 2019
Konu: İnşaat Mühendisliği = Civil Engineering

Özet:
Tarihe bakıldığında insanlık gerek ekonomik gerek sosyal yaşantılarını iyileştirme adına çevresini kendi amaçları doğrultusunda değiştirmiştir. 1900'lü yıllardan sonra insan nüfusunda yaşanan yüksek artışla beraber günümüzde milyonlarca insanın yaşadığı büyük şehirler kurulmuştur. Ayrıca bu şehirler zaman içerisinde gelişen imkânlar ile sürekli bir değişim ve gelişim içerisindedirler. İstanbul Türkiye'nin tarih, ekonomi, nüfus vs. açısından en önemli şehridir. Bunun yanında konumu itibariyle yüksek deprem riski olan bir bölgede yer almaktadır. Deprem mühendisliği, son 50 yıl içerisinde çok önemli gelişmelerin olduğu bir alandır. Teknolojinin kazandırdığı imkânlar ile geçmişte inşa edilen yapıların güncel durumlarının tespiti ve yeni bulgular doğrultusunda değerlendirilmesi bir ihtiyaçtır. Bu çalışma kapsamında şev stabilitesi ve değerlendirilmesi konusunda bir araştırma yapılmış ve literatürde kabul gören analiz yöntemleri hakkında bilgi verilmiştir. Sonrasında ise İstanbul Eminönü semtinde, Haliç kıyısında dolma zeminler üzerine zemin iyileştirmeleri yapılarak inşa edilen bir yapıya yönelik incelemeler yapılmıştır. Bu incelemelerde zemin etütleri yapılmış ve eski dokümanlar incelenerek saha zemini modeli oluşturulmuş, limit denge ve sonlu elemanlar yöntemleri kullanılarak statik ve sismik durumda stabilite analizleri yapılmış, elde edilen bulgular yorumlanmıştır.

Abstract:
Humanity has changed the environment for its own purposes in order to improve its economic and social lives throughout the history. After 1900s, big cities where millions of people live have built with high increase in human population. Additionally, the cities are continuously evolving and growing by means of developments in potential. İstanbul is the most important city of Turkey in terms of history, economy, population etc. Besides, İstanbul is located high-risk earthquake zone. Earthquake engineering is a discipline that has many important findings in last 50 years. Utilizing the technology is a requirement for the determination of status of old applications and the evaluation on the existing structures. In the scope of this study, a research on slope stability and its evaluation topics is made and accepted methods on analysis in the literature are conveyed.  Afterwards, investigations are executed for a building that has been constructed on improved fill units at the coastal line of Golden Horn, Eminönü, İstanbul. In the scope of these investigations, geotechnical soil model is created as using the results of performed soil investigations and reviewed old documents. Stability analyzes are performed as using limit equilibrium and finite element methods for both static and seismic cases and interpreted results are presented.
In the first part of this study, it is duscussed why slope stability is a need for our lives. Determination of the current situation and developments in the field are conveyed. It is mentioned how utilizing the computing technology in engineering calculations and increasing investigation alternatives provide unprecedented advantages to professionals. 
In the second part, a literature research study about slope stability is conveyed. At the beginning of this part, concept of slope stability is explained. It is showed that the cost of the slope failures in our lives with true stories. Disasters which are caused by slope stability problems and great losses are mentioned. The effects which causes slope problems are discussed. Relationship between slope stability problems and earthquakes is discussed and developments in the field of earthquake engineering in Turkey are conveyed. Then, mentioned that the studies on the classification of slope failure types such as sliding, lateral spreading, falling etc. After an explanation of  general approach, slope failure types are explained in detail one by one. 
In the third part of the study, evaluations to determinate the stability condition of slopes are mentioned. What the stability of a slope depends on are discussed. Circumstantial evidences of a slope failure are mentioned such as tension cracks, tilted trees and piles etc. Observation techniques and alternatives are discussed. Those techniques are wide variety and multidisciplinary. Instrumentation and monitoring methods are quite advanced and usefull for observation of  a slope nowadays. Additionally, utilizing the photogrammetric methods and geophysical methods are mentioned as usefull for this purpose. After the observation part, in-situ and laboratory testing for slope stability evaluations are touched upon. Following the data collection part, approaches for the numerical analysis of the slope stability problems are explained under two main parts limit equilibrium analyses and stress-deformation analyses.
At the beginning of the limit equilibrium analyses, concept of factor of safety is explained and different approaches to obtain factor of safety are conveyed. Assumpsions and the limits of the method are talked over. Several methods, which are proposed by important engineers and researchers, to calculate the factor of safety of a slope are also conveyed under this section.
After the section of limit equilibrium analyses, section of the stress-deformation analyses was  started. In the first part of this section, fundamentals of the concept are conveyed. Advantages and disadvantages of the stress-deformation analyses over limit equilibrium analyses are discussed. Because of the widespread usage of finite element method in stress-deformation analyses, finite element method is touched upon in this section.
Following explanation of the analysis fundamentals, getting more specific, seismic slope stability analyses are mentioned. In the beginning, reasons of the earthquake induced slope failures are discussed. It is mentioned that seismic slope failures can be examined under two main concept. One of them is inertia forces induced failure, and other one is failure due to reduction in strenght under cyclic loading condition. Those approaches are explained under this section of the thesis.
In the fourth part, a case study, that consists of a desk study on old articles, geotechnical soil investigations, seismicity of the study area, geotechnical modelling of a slope,  numerical analyses, is conveyed. 
Desk study was about an article which was written by Hamdi Peynircioğlu. In the article, soil improvement works, that were performed during and after the construction of the building in the study area, are mentioned. 
Afterward, performed soil investigation works are conveyed. In the scope of the soil investigations, ten boreholes are drilled (four of them on the Golden Horn and six of them on land). Standard penetration tests, pressuremeter tests are performed in the boreholes. Under the scope of the laboratory tests, various soil mechanics experiments are performed. Additionally, three different geophysical measurement method (ground penetration radar, MASW, PS-logging) are applied. As using the soil investigation data, a consistent geotechnical model of the study area is created.
In the final part of the case study, numerical analyses are performed as using the created geotechnical model of the slope. In order to conduct analyses, several limit equilibrium methods and finite elemnent method are used in both seismic and static cases. Fellenius Method, Simplified Bishop Method , Janbu Method,  Spencer Method are used for the limit equilibrium analyses in SLIDE software. PLAXIS 2D software is used for the finite element method based analyses.
As a result of the analyses, it is determined that there is no slope problem in static case. On the other hand, both limit equilibrium analyses and finite element analyses showed that there would be a slope stability problem in the case of earthquake. In the seismic case, factor of safeties were aproximately 0.5 in limit equilibrium analyses, and the deformations on the slope surface are calculated between 1.69m and 3.29m in finite element analyses. 
In this thesis, it is tried to be created numerical soil models consistent with each others as using data coming from many different sources. And those models are analyzed. As a result of the analyses, it is seen that could be possible to occur serious deformations at the study area in case of earthquake.