Evaluation of collapse mechanism and portal interaction of a High-Speed Railway Tunnel (T29 Tunnel, Turkey)

Abstract

Within the scope of the Ankara-Istanbul High Speed Train Project, the T29 tunnel was opened to traffic after completing excavation and support implementation. The tunnel was excavated in weak to very weak graphitic schists causing severe face stability problems and deformations on the tunnel supports during excavation stage. In the progress of the excavation stage, a serious face failure occurred at Km: 225 + 784, and the effects of this face failure were observed on the surface. Since the cover thickness is approximately 35 m in this section of the tunnel, it was decided to pass this zone with a cut and cover structure. The portal excavation was carried out from the failure zone, and it was planned to provide stability with the closure of the surface by constructing a cut-and-cover structure immediately afterwards. However, slope failures occurred during the portal excavations. This section was reworked, and it was decided to support this area with a pile system. Consequently, in this study, the reasons for the face failure and slope failures are investigated, and the construction stages are explained and discussed.

Şehir İçerisinde Açılan Tünellerde Portal Şev Stabilitesi ile Tünel Kazı İlişkisine Bir Örnek (T7 Tüneli, Ankara-Sivas Yüksek Hızlı Tren Projesi (Kayaş-Elmadağ Kesimi))

“…Portal şevlerinde karşılaşılan sorunlar incelendiğinde genelde uzun dönemde portal şevlerinin stabilitesini yitirmesi sonucu meydana gelen yenilmeler ile tünel kazısı sırasında meydana gelen deformasyonların sonucu portal şevlerini olumsuz etkilemesidir ( [4], [5], [6], [7], [8], [9]). Zira kısa dönemde portal şevleri stabilitesi sağlansa da tünel uzunluğuna bağlı olarak değişen inşaat süreleri dikkate alındığında uzun dönemde yenilmelerin meydana gelmesi kaçınılmazdır.…”