Investigation of the Effect of Tunnel Geometry on Deformations in Shallow and Stratified Rock Formation

Year 2022, Volume: 27 Issue: 3, 548 - 556, 25.12.2022

Kübra Nur Adlım Sinem Bozatlı Yavuz Abut

https://doi.org/10.53433/yyufbed.1090576

Abstract

Deformations in the tunnel occur as a result of surcharge load from the structures on the surface, overloading, internal stresses in the rock or soil, and other factors. In-tunnel deformation measurement is important to determine the magnitude of plastic deformation in the tunnel and is an important step in monitoring tunnel safety. In this study, three-dimensional and non-linear behavior of tunnels designed as horseshoe or egg shape in a groundwater environment in a four-layered rock formation and gradually excavated with NATM (New Austrian Tunneling Method) principle were analyzed using the finite element method. The tunnel crown and wall, which were exposed to different loading conditions according to the excavation steps, were examined in detail in terms of permanent deformations. In addition, thanks to the deformation curves, the permanent deformations occurring along the critical sections of the tunnel during all excavation stages were compared relatively for both tunnel geometries. It has been determined that it is more advantageous to choose the tunnel geometry as egg-shaped rather than horseshoe type for reducing the settlement and the convergence in the shallow and layered rock environment.

Keywords

Convergence, Deformation, Settlemet, Tunnel design

Tünel Geometrisinin Deformasyonlar Üzerindeki Etkisinin Sığ ve Tabakalı Kaya Ortamında İncelenmesi

Abstract

Tünel içindeki deformasyonlar, üst yapıdan gelen sürşarj yükü, aşırı yükleme, kayaç veya zemin biriminde oluşan içsel gerilmeler ile diğer faktörlerin bir sonucu olarak ortaya çıkar. Tünel içi deformasyon ölçümü, tüneldeki plastik şekil değiştirmenin büyüklüğünü belirleyebilmek için önemlidir ve tünel güvenliğinin izlenmesinde önemli bir safhayı oluşturur. Bu çalışmada, dört tabakalı bir kaya formasyonunda ve yeraltı suyu etkisinde bulunan, at nalı veya yumurta şeklinde tasarlanan, NATM (Yeni Avusturya Tünel Açma Metodu) tekniği ile kademeli olarak açılacak olan tünellerin üç boyutlu ve doğrusal olmayan davranışları sonlu elemanlar yöntemi ile analiz edilmiştir. Kazı adımlarına göre farklı yükleme koşullarına maruz kalan taç ve tünel çevresinde meydana gelen kalıcı deformasyonlar ayrıntılı olarak incelenmiştir. Ayrıca her iki tünel geometrisinde, bütün kazı aşamalarında tünelin kritik kesitleri boyunca oluşacak olan kalıcı şekil değiştirmeler, deformasyon eğrileri sayesinde göreli olarak karşılaştırılmıştır. Sığ ve tabakalı kaya ortamında tasman ve konverjans miktarının azaltılmasında, tünel geometrisinin at nalı tipi yerine yumurta şeklinde seçilmesinin daha avantajlı olduğu tespit edilmiştir.

Keywords

Deformasyon, Konverjans, Tasman, Tünel tasarımı

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