Tez özetleri Astronomi ve Uzay Bilimleri Anabilim Dalı

Possıble Geotechnıc Problems To Be Encountered At Bosphorous Straıt Tube Tunnel Project

One of the most important projects of the world, Marmaray Project, aims not changing the roads which have the properties of high capacity, not contaminating the environment by using electrical energy and reducing the dependence on individual transportation and highway into parking lots in order to offer a modern city life and urban transportation possibilities to the citizens and to preserve the natural historical properties of the city. This project, which is going to connect Halkalı district in European side and Gebze district in Asian side by means of a continuous, modern, high-capacity suburb railway system depends on improvement of suburb railway system in İstanbul.

Bosphorous immersed tunnel part of Marmaray Project is discussed in this project. This system has many examples worldwide but it will be used in Turkey for the first time. Most important property of Marmaray keeping it apart from its similar examples is that it is the deepest immersion tunnel in the world. The depth of the tunnel reaches 70 m by Bosphorous pass.

Geotechnical operations made on the tunnel route have also guided this project. Results of the tests (in-situ tests and laboratory tests) made showed us that ground of Bosphorous has inconveniences. Data used in this work combined under 3 groups. These are the studies caried out in years1986,2003 and 2004. These studies consist of labratory experiment results taken place at the same time with 18 number SPT, 22 numbers CPT and site experiments.

The liquefaction risk of Bosphorous sediments when a strong earthquake takes place is the leading problem. Work method using for liquefaction analysis; these are the analysıs that with respect to method of Seed et al. and of Ambraseys liquefaction analysis by using SPT data and labratory results, with respect to method of Robertson & Wride and of Juang liquefaction analysis according to CPT data and labaratory results. Liquefaction analysis methods using labratory data are Modified Chinesse Criteria and Grain Size Gradation. In accordance with these analysis there heve been made assesment of liquefaction along to İmmersed Tube Tunnel

Acording to analysis results Bosphorus Sediments have potential liquefaction risk on the eastern and the central part of Bosphorus.When we look at the results taken from the analysis the the values from the firs 15 m can be neglected because when İmmerese Tube Tunnels are being sunk, the ground excavated up to these deep.In general soil has a liquefaction risk between 15-20 meters and 25-30 meters.

When we comparing the analysis,the situation we faced; is same qu and fs values are in different values. Generally in method of Robertson and Wride againts to Juangs method in shallow grounds the liquefaction exist less in comparison in deeper grounds more liquefaction risk can be calculated.

In comparison of SPT and CPT methods, the advantegous of method using SPT results; because of common use of this experiment access to data is easy and value N(1,60)cs=30 is very close to limit and thats way can be made an assesment in the site close to real. Otherwise the disadvantegous of this method is the error percentage becomes higher because of human factor.

The advantageous of the liquefaction methods using CPT values ; by finding the Ic value the calsification of the soil can be made, experiment can be done without specimen, electronically achived values decrase the error factor. The disadvantageous is the less usage of CPT with respect to SPT and too much formulas in CPT method

For the safety of Immerse Tube Tunnel there must be ground improvement where there find out liquefaction risks.