Comparison of Mohr-Coulomb and Hardening Soil Models’ Numerical Estimation of Ground Surface Settlement Caused by Tunneling

Year 2017, Volume: 7 Issue: 4, 95 - 102, 31.12.2017

Semet Çelik

Abstract

Due to in depth tunnel excavation, tensions in the soil are eased, causing elastic and plastic

deformations in the area of tunnel and leading to surface settlement at the ground level. Currently, along with

the use of numerical methods in analysis and design of engineering projects, it is known that this method has

used extensively in the analysis of problems related to geotechnical engineering and tunneling. Selection of the

appropriate parameters and soil model can have a significant impact on the results of numerical analysis. The

Mohr-Coulomb elastic-plastic model (MC) is one of the most widely used models, used in cases evaluating the

hardness of materials, independent of the surface tension. If the Mohr-Coulomb used for numerical modeling

of tunnel where in-depth tunneling excavation is involved and where an increase in maximum ground surface

settlement and decrease in the reliability of stability of tunnels can be seen, which may not be appropriate in some

conditions. The more appropriate model should be used to solve this problem, one that can model the hardness of

materials based on changes in the level of stress. In this study, the maximum ground surface settlement due to tunnel

excavation, obtained from Mohr- Coulomb model was compared with those of Hardening Soil (HS) Model results.

Therefore, the ground surface settlement because of an assumption tunnel in different depths was analyzed with

Mohr-Coulomb and Hardening Soil models by using PLAXIS 2D. As a result of the analyzes, it is observed that as

the depth of the tunnel increases, the settlements on the ground surface decrease according to Mohr-Coulomb and

approach the real values.

Keywords

Finite element method, material models, plaxis, surface settlement, tunneling

Tünel Kazısından Dolayı Zemin Yüzeyindeki Oturmaların Mohr- Coulomb ve Pekleşen Zemin Modelleriyle Nümerik Tahminlerinin Karşılaştırılması

Abstract

Zemin içinde yapılan tünel kazısı nedeniyle, zemindeki gerilmeler boşalarak kazı alanında elastik ve plastik

deformasyonlara yol açmakta ve zemin yüzeyinde oturmalar meydana gelmektedir. Günümüzde, mühendislik

projelerinin tasarım ve analizinde sayısal yöntemlerin kullanımı ile birlikte, Geoteknik mühendisliği ve tünel ile ilgili

problemlerin çözümünde bu yöntemin yaygın bir şekilde kullanıldığına tanıklık etmekteyiz. Uygun parametrelerin

ve zemin modelinin seçilmesi, nümerik analiz sonuçlarını üzerinde önemli etkiye sahiptir. Mohr-Coulomb (MC)

elasto-plastik model malzemelerin sertliğinin yüzey gerilmelerden bağımsız olarak tanımlandığı durumlarda

kullanılan en yaygın zemin davranış modellerinden biridir. Tünel modellemelerinde Mohr-Coulomb kullanılması

halinde, kazı derinliği arttıkça zemin yüzeyindeki oturmaların gerçek değerlerden fazla çıktığı ve güvenilirliğin

azaldığı görülmektedir. Bu problemin çözümü için, gerilme düzeyindeki değişikliklere bağlı olarak malzemelerin

sertliğini modelleyebilen daha uygun bir davranış modeli kullanılmalıdır. Bu çalışmada, tünel kazısından dolayı

Mohr-Coulomb modelinden elde edilen maksimum zemin yüzey oturmaları Pekleşen Zemin modeli (HS) ile

karşılaştırılmıştır. Bu nedenle, varsayılan farklı derinliklerdeki bir tünelden dolayı zemin yüzeyinde oluşacak

oturmalar PLAXIS kullanılarak Mohr-Coulomb ve Pekleşen Zemin malzeme modelleriyle analiz edilmiştir.

Yapılan analizler sonucunda, Pekleşen Zemin modelinde tünelin derinliği arttıkça zemin yüzeyindeki oturmaların

Mohr-Coulomb’a göre azaldığı ve gerçek değerlere daha yaklaştığı görülmektedir.

Keywords

Sonlu elemanlar metodu, malzeme modelleri, plaxıs, yüzey oturması, tünel

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