EFFECT OF TWIN TUNNEL GEOMETRY ON LINING PERFORMANCE AND GROUND SETTLEMENT: A CASE STUDY

Abstract

The increasing need for urbanization has led to the construction of numerous tunnels in urban areas to meet growing transportation demands. A distinctive feature of urban traffic tunnels is the construction of two parallel tunnels located in close proximity to one another. Investigating the mechanical interaction between these twin tunnels during the design phase is crucial. This study employs the finite element method to investigate the mechanical interaction between twin tunnels, extending the study of the deflection angles between the two tunnels at the B-B section of Metro Line No. 1 in Ho Chi Minh City, Vietnam. The key findings are as follows: The normal forces in the lining of the upper tunnel reach their maximum when the offset tunnel configuration has an angular relative position of α = 30°. For piggyback tunnel geometries, increasing depth results in the highest magnitude of normal forces in the lining of the lower tunnel. Due to tunnel interaction, the maximum bending moments in both the upper and lower tunnel linings occur in the offset tunnel configuration with α = 45°. The maximum ground surface settlement caused by twin tunnel construction is greater than that of a single tunnel in greenfield conditions. The side-by-side tunnel configuration results in the smallest ground settlement, while the offset arrangement with α = 60° results in the largest ground settlement. These findings provide valuable insights for the design and construction of twin tunnels in urban environments, emphasizing the importance of understanding tunnel interaction under different configurations.