Restorative Design of Underground Structures Damaged by Kahramanmaras (Turkey) Earthquakes on 6 February 2023: A Case Study on Erkenek Highway Tunnel

On 6 February 2023, two consecutive earthquakes, with magnitudes of 7.8 and 7.7 (Mw), struck Kahramanmaras Province in the Mediterranean region of Turkey. A thorough evaluation of post-seismic damage to underground structures is critically important for ensuring both structural safety and operational serviceability. Focusing on the Erkenek Tunnel, this study provides a systematic investigation to assess the impact of the devastating Kahramanmaras earthquakes on highway tunnels. The tunnel sustained significant damage, primarily concentrated in its inner lining structures, and as a result, its left tube was shut down for service. Based on the in situ observations, geological conditions, initial design documents and construction techniques, a numerical analysis was conducted to model critical tunnel sections and evaluate their structural stability. Considering both static loads and seismic forces, restoration design works, techniques and construction sequences are recommended for the damaged sections of the Erkenek Tunnel. As the earthquake damage sustained by underground structures is a rare case, the methodology and findings of this study regarding post-seismic tunnel inspections and rehabilitation designs shed light on the maintenance works of in-service tunnels in earthquake-prone zones.