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|Title:||Diyafram Duvarlı İksa Perdelerinde Meydana Gelen deplasmanlar İle İlgili Parametrik Bir Çalışma|
|Other Titles:||A Parametric Study On Displacements Occurring At shoring With Diaphragm Walls|
İlhan Demir, Didem
|Publisher:||Fen Bilimleri Enstitüsü|
Institute of Science and Technology
|Abstract:||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 meydana gelen 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 olarak bahsedilmiştir. 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.|
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. Uncontrolled urbanization 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-storey buildings in small areas and construction of under ground structures via deep excavations. Therefore deep excavation has become one of the focal points of the geotechnical 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. xxii 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.
|Description:||Tez (Yüksek Lisans) -- İstanbul Teknik Üniversitesi, Fen Bilimleri Enstitüsü, 2015|
Thesis (M.Sc.) -- İstanbul Technical University, Instıtute of Science and Technology, 2015
|Appears in Collections:||İnşaat Mühendisliği Lisansüstü Programı - Yüksek Lisans|
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