Estimation of surface displacements due to tunnel construction

Tunnels have been preferred from past to present for various purposes such as reducing traffic congestion in highly populated areas, facilitating passage through rugged terrains, enabling the transit of various infrastructure lines, and preserving natural areas. Due to their significant interaction with the ground, tunnels are distinct from other engineering structures in terms of seismic, geological, and geotechnical engineering. Parameters such as ground formation, excavation method, and support model directly impact the tunnel. It is common to encounter some deformations in the rock and ground surface during construction. While these deformations may dissipate over time in some cases, in others, they may exceed the plastic limit and cause permanent damage. To predict potential risks and take necessary precautions, geotechnical investigations must be conducted meticulously. In this study, the tunnel project under construction on the Kırkdilim route in Laçin District of Çorum Province by the General Directorate of Highways was examined. Numerical calculations were performed considering the ground structure, construction method, and support elements used in the project. Due to its spiral structure and sharp curves, the Kırkdilim route is prone to frequent traffic accidents; hence, a twin-tube tunnel is being constructed using the New Austrian Tunneling Method (NATM). Deformation analysis was conducted using the Finite Element Method (FEM) in the PLAXIS 2D program, and the calculated values were compared with field deformation measurements. It was found that the differences between the two sets of values were negligible and the analyses provided realistic results. The analyses facilitated the assessment of potential deformations that could occur before, during, and after the excavation, thereby allowing for the evaluation of necessary measures to prevent potential collapses and swelling.