Limitations in Tunnel Portal Design: An Evaluation Using Numerical Models and Line Surveys

Year 2024, Volume: 48 Issue: 1, 1 - 18, 26.06.2024

Ozgur Satıcı

https://doi.org/10.24232/jmd.1385219

Abstract

In this study, the engineering geology and the geotechnical design studies of the Aslankayası Tunnel Project are explained. Owing to the low overburden thickness, the tunnel in question, which is located near a slope face, will be exposed to asymmetrical loading after commencement of excavation. The asymmetrical loadings will especially affect the right tube, in the direction of increasing kilometer markings. Furthermore, the thickness between the right tube’s right wall and the slope face in this section has decreased down to 6 m. Moreover, as the tunnel is passing under a 1st degree protected archeological area. Some of the site investigation studies, such as geotechnical drilling and site laboratory works, could not be performed. The excavation support system of the tunnel was determined using empirical studies and numerical models with the help of line surveys, local sampling, and internationally accepted rock mass classification studies (RMR, Q, GSI). These studies were performed on rock mass outcrops. Rock mass engineering properties were determined through the utilization of empirical equations that incorporate data derived from site investigation studies and laboratory test results as input. By using geotechnical properties obtained from line surveys and engineering geology studies, a numerical model was generated. The numerical model results corroborated the asymmetrical loading predictions obtained from line surveys and engineering geology studies. The main aim of this study is to emphasize the importance of interpretation of the geological units and their post excavation behaviors on the excavation stability.

Keywords

Line surveys, Numerical modeling, Rock mass classifications, Slope tunnel design

Tünel Portal Tasarımında Kısıtlar: Sayısal Model ve Hat Etütleri Kullanarak Bir Değerlendirme

Abstract

Bu çalışmada Aslankayası tünel projesine ait mühendislik jeolojisi ve jeoteknik tasarım çalışmalarını anlatmaktadır. Düşük örtü kalınlığı nedeni ile şev yüzeyine yakın olan yamaç tüneli, özellikle kazı işlemine başladıktan sonra asimetrik yüklemeye maruz kalacaktır. Asimetrik yükleme, proje artış kilometresi yönünde özellikle sağ tüpte etkili olacaktır. Ayrıca, bu bölgedeki sağ tüp sağ duvarı ile yamaç yüzeyi arasındaki et kalınlığı 6 m seviyesine kadar düşmektedir. Ayrıca, tünelin 1. derece arkeolojik koruma alanı altından geçiyor olması nedeniyle, tünel ekseni üzerinde yapılması gerekli olan bazı saha araştırma çalışmaları, örneğin jeoteknik sondaj çalışmaları ve ilgili saha deneyleri yapılamamıştır. Tünelin kazı destek sistemi; hat etütleri, yerinden örnek alma ve uluslararası kabul görmüş kaya sınıflama sistemleri kullanılarak (RMR, Q, GSI) ampirik çalışmalar ve nümerik modellemeler aracılığı ile belirlenmiştir. Bu çalışmalar için sahada yüzlek veren kaya kütlesi kesimleri kullanılmıştır. Saha çalışmalarından ve laboratuvar testlerinden elde edilen sonuçlar girdi olarak kullanılarak ampirik eşitlikler yardımı ile kaya kütlesi mühendislik parametreleri hesaplanmıştır. Hat etütleri ve mühendislik jeolojisi çalışmalarından elde edilen veriler ile nümerik modeller oluşturulmuştur. Nümerik modellerden elde edilen sonuçlar, mühendislik jeolojisi aşamasında asimetrik yükleme koşullar için yapılan tahminleri doğrulamıştır. Bu çalışmanın esas amacı da jeolojik birimlerin ve onların kazı sonrası davranışlarının doğru yorumlanmasının tünel kazı stabilitesi üzerindeki önemini göstermektir.

Keywords

Hat etütleri, Sayısal modelleme, Kaya kütle sınıflamaları, Yamaç tünel dizaynı

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