Re-design of a railway tunnel intersected by surface rupture of the Erkenek fault segment during the 6 February 2023 Pazarcik (Mw 7.7) Earthquake (Türkiye)

Abstract The T3 Tunnel on the Malatya-Narlı Conventional Railway Route was intersected by the surface rupture during the February 6, 2023 Pazarcık Earthquake (Mw 7.7), and a part of the tunnel was damaged completely. In this study, the investigation results, and re-design of the tunnel, are presented. The T3 Tunnel, which was built in 1933 with interlocking stone masonry lining, was cut by the Erkenek fault, one of the segments of the East Anatolian Fault Zone (EAFZ), and a landslide was triggered around the tunnel portal. Under the influence of these two factors, collapse, and various deformations occurred in the tunnel. To understand the character of the failure, detailed geological, geophysical, and geotechnical studies were carried out in addition to in-situ observations. Subsequently, the tunnel was re-designed and repaired to open the railway to service. For this purpose, a re-design project was developed that included 2-stage engineering solutions including on-tunnel and in-tunnel construction efforts. In the first stage, the portal landslide was rehabilitated using support systems, and in the second stage, tunnel consolidation injection, redesign of the portal structure, and reconstruction of the tunnel support system were carried out. The obtained data and scientific evaluations are presented together with analyses. It is of vital importance that transportation structures continue to function during and after earthquakes. Therefore, the case presented in the study is one of the rare and interesting cases in terms of tunneling literature. The construction efforts in the T3 Tunnel were completed without any problems 6 months after the earthquakes, while more than 30,000 aftershocks continued.