Özet:

Portal sections in tunnels have always been within critical engineering structures. The interaction of the portal and tunnels affects both the portal design and the tunnel design. Since the effect of a possible failure in the portal slopes directly affects the tunnels, it also negatively affects the progress in the tunnel and stops it sometimes. Considering that the excavation and support work in long tunnels may take years, the stability of the portal slopes gains great importance. The failures that will develop due to discontinuities in the tunnels excavated in the rock units and the failures that occur as a wholescale collapse in the portal slopes in weak soils should be evaluated according to the long term. In addition, a more critical situation occurs when there are residential areas around the portal. Within the scope of this study, this situation is investigated specifically for the T7 tunnel constructed within the scope of Ankara-Sivas High Speed Train Project, Kayaş-Elmadağ section. With the effect of the deformations that occurred during the tunnel excavation, the tunnel lost its stability and the tunnel excavation was stopped. The tunnel supports were renewed, negatively affecting the stability of the portal. In addition, the fact that there is a settlement in the tunnel entrance portal section has increased the importance of this situation. For this purpose, numerical analyzes were performed for the portal and tunnel supports, and the stability of the current situation was evaluated, and then a methodology was proposed for the portal section with new support systems.