Diyafram duvarlı iksa perdelerinde meydana gelen deplasmanlar ile ilgili parametrik bir çalışma
A parametric study on displacements occurring at shoring with diaphragm walls
Yazar: DİDEM DEMİR
Danışman: YRD. DOÇ. DR. BERRAK TEYMÜR
İstanbul Teknik Üniversitesi / Fen Bilimleri Enstitüsü / İnşaat Mühendisliği Ana Bilim Dalı / Zemin Mekaniği ve Geoteknik Mühendisliği Bilim Dalı
Derece: Yüksek Lisans, 2015
Konu: İnşaat Mühendisliği = Civil Engineering

Özet:
20. yüzyılda sanayileşme ve ekonominin gelişmesine bağlı olarak kentleşme büyük
bir hızla artış göstererek, büyük kentler meydana gelmeye başlamıştır. Kentleşmenin
önlenemez artışı sonucu yaşanan arsa krizleri, küçük alanlarda çok katlı binaların
yapılmasına ve otopark gibi alanların yeraltına taşınmasına neden olmuştur.
Böylelikle günümüzde sıkça kullanılmakta olan derin kazıların yapılması konusu
mühendislik çalışmaları açısından önemli bir noktaya gelmiştir.
Bu çalışma, derin kazı destek sistemlerinden biri olan diyafram duvarlı iksa
perdelerinde meydana gelen deplasmanlar ile sahada ölçülen deplasmanların
karşılaştırılması ve değişen zemin parametrelerinin deplasmanlar üzerindeki
etkilerinin incelenmesi amacıyla hazırlanmıştır.
Yapılan çalışmada, öncelikle derin kazı destek yöntemleri ana hatları ile
açıklanmıştır. Daha sonra diyafram duvarlı iksa perdelerinden detaylı biçimde
bahsedilmiştir. Destekli kazıların gözlemlenmesi amacıyla kullanılan yöntemler
ile ilgili genel bilgeler verilmiştir. Özellikle inklinometreler ile iksa 
sisteminde meydanagelen deplasmanların gözlemlenmesi üzerinde durulmuştur.
Tez kapsamında, incelenen iksa projesi ile ilgili bilgiler (kazı planı, zemin
profili ve kesitler) verilmiştir. Sonlu elemanlar yöntemi ve Plaxis programından
genel olarakbahsedilmiştir. Ardından Plaxis analizlerinden elde edilen deplasmanlar
gösterilmiştir. Sahada ölçülen deplasmanlar verilerek, hesaplanan deplasmanlar ile
karşılaştırılmıştır. Belirlenen ve ölçülen deplasman değerlerinin kesitlerin çoğunda
birbirine yakın olduğu, birkaç kesitte ise Plaxis analizlerinden elde edilen
deplasmanların ölçülenlere oranla daha fazla olduğu gözlenmiştir.
Çalışmanın son kısmında tasarım aşamasında belirlenen zemin parametrelerini (içsel
sürtünme açısı, elastisite modülü ve kohezyon) belirli oranlarda arttırarak parametrik
bir çalışma yapılmıştır. Arttırılan zemin parametrelerine göre yeniden yapılan
analizlerde, farklı deplasmanlar elde edilmiştir. Buna göre, zemin parametrelerinin
değişiminin deplasmanlar üzerindeki etkileri değerlendirilmiştir. Deplasmanlar
dışında zemin parametrelerinin değişimi sonucunda diyafram duvarda meydana
gelen moment ve kesme kuvvetleri de incelenmiştir. Bu değerler dizayn aşamasında
elde edilen moment ve kesme kuvvetleri ile karşılaştırılmış ve meydana gelen
değişim gözlenmiştir.

Abstract:
Urbanization is a phenomenon dating back to the early stages of humanity.
Depending on the development of industrialization and urbanization, the economy
has improved, so that large cities have occurred. In the first quarter of the 
twentyfirst century, urbanization move ahead of industrialization in Turkey. 
Uncontrolledurbanization has brought, with it increasing population growth, the 
need for land;land values have increased dramatically in order to meet the demand 
with the supply.Land crisis was able to take a breath as a result of construction
of multi-storeybuildings in small areas and construction of under ground structures
via deepexcavations. Therefore deep excavation has become one of the focal points 
of thegeotechnical engineering.
In order to perform deep excavations, shoring system is needed. Today, deep
excavation can be made with different shoring systems. Most preferred ones are mini
piles, bored piles, secant piles and diaphragm walls. Mentioned systems are vertical
supports and as bearing system they are cantilever and can also be supported by
prestressed anchors or struts.
Taking into account the soil profile in the excavation region, groundwater level,
depth of the excavation, neighboring structures and environmental factors, most
accurate shoring system should be preferred to be safe and economical. Otherwise,
the stress increase in the ground and settlements in neighboring buildings due to
long-term draining of groundwater may occur. To design safe and economical
shoring system, selected parameters and assumptions made should be close to reality.
In result of the excavation of the multi-storey buildings with multiple basement, very
high stresses occur. In this case, the diaphragm walls are one of the most safe system
that can be preferred. Diaphragm walls are more rigid compared to the pile system
and also allows observation of displacements that occurs during excavation. These
displacement can be determined with inclinometers. Shoring system should be kept
under control by comparing horizontal and vertical displacements obtained by
instrumental observations made with inclinometers and the displacements specified
during project.
This study has been prepared to compare displacements that were calculated in
shoring system with diaphragm walls, a type of deep excavation support system, with
the displacements measured in the field; and to investigate the effect of changing soil
parameters on the displacements. In this study, deep excavation support methods are
outlined first. Then the support system used in this thesis which is diaphragm walls
are discussed in detail.
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General information about the methods used to observe the excavations has been
given. In particular, the information focuses on monitoring the displacements that
occurs in shoring systems via inclinometers.
An example of a shoring application is analyzed by a finite element software
program namely Plaxis. At this stage, general information about the project is given.
The soil profile, the excavation depth and sectional properties are presented.
In the thesis, the finite element method and Plaxis program are explained briefly.
Then displacements obtained from Plaxis analysis are shown in different sections.
Then displacements measured in the field are compared with the calculated
displacements. In most of the sections, measured and calculated displacements are
close to each other, in several sections, displacement results from Plaxis analysis are
greater compared to the displacements measured in field.
In the last part of the study, a parametric study conducted by proportionally inreasing
the soil parameters (internal friction angle, elasticity modulus and cohesion)
determined in the design phase. Different displacements were obtained according to
the analysis with increased soil parameters. The effect of changes on soil parameters
on displacements were investigated.
Besides displacements, moments and shear forces occurred in diaphragm wall as a
result of change of soil parameters are also investigated. These values are compared
with the moments and shear forces calculated at the design stage and changes in the
results are observed.
During design process, idealized soil profile and determined soil parameters (internal
friction angle, elasticity modulus and cohesion) and evaluation of the results obtained
with great care is one of the most important factors of modeling close to reality.
Otherwise over designed projects can be done and they can be uneconomical. Also
under designed projects may result with hazardous situation threatening life and
property.
According to the analysis carried out within this thesis, it is observed that the
calculated displacements and measured displacement were close to each other. But in
some sections (Section 1, Section 2 and Section 4) displacements calculated by
Plaxis program seem to be slightly higher compared to the measured displacements.
In order to see the impact of changes of soil parameters on diplacements, internal
friction angle, modulus of elasticity and cohesion values increased by 5% 15% 25%
and new analysis for all sections were made.
The results of the analysis can be summarised as follows;
- Increasing the angle of internal friction in the fill has caused decrease in the
calculated displacements.
- Increasing the modulus of elasticity of the fill did not cause a significant difference
in the calculated displacements.
- Increasing the angle of internal friction in rock did not cause a significant
difference in the calculated displacements.
- Increasing the elasticity modulus of the rock has caused decrease in the calculated
displacements.
- Increasing the cohesion of the rock did not cause a significant difference in the
calculated displacements.
xxiii
With respect to the analysis on sections, for fill, internal friction angle, for rock, the
modulus of elasticity can be effective on displacements. On the other hand the
displacements obtained from parameters specified in the design phase and the
displacement measured in field are close values. In some sections, it seems that the
displacements measured in the field are smaller. Accordingly, it is seen that the
system is generally formed in an economical and safe way.
In addition, the effect of changes in soil parameters on shear forces and moments
were investigated.
According to the analysis;
- Increasing the angle of internal friction in the fill has led to a reduction in moment
and shear forces in Section 1, Section 4 and Section 4a.
- Increasing the modulus of elasticity in the fill has cause a decrease in moment, but
no change in shear forces in Section 2, Section 3 and Section 5.
- Increasing the angle of internal friction in rock did not cause a significant
difference in shear forces and moments.
- Increasing the elasticity modulus of the rock does not lead to a noticeable
difference in the shear forces and moments.
- Increasing cohesion in rock did not cause a significant difference in shear forces
and moments.
Increase in the cohesion of rock did not cause a significant diffence in shear forces
and moments. During execution of deep excavations, occurring displacements should
be observed with instruments to provide safety and to be able to project against any
potential risks. Any loss of life or property can be avoided by taking precautions for
risk factors as result of observations.
In conclusion, the selection of the correct soil parameters at design state is essentially
important for design to be realistic, safe and economical. Because in civil
engineering applications soil conditions are known to have significant effect on
engineering designs and construction methods.
In order to determine the correct soil parameters, detailed soil surveys should be
made primarily. Then, obtained data should be analyzed correctly and should be
interpreted accordingly. Selection of the correct soil parameters is one the most
important factors in the design state. Otherwise, the design would be devoid of the
reality.