Influence of Tunnel Geometry on Collapse Behaviour: A Numerical Study

Abstract

Tunnel collapse is a common concern in underground construction, especially when tunnels are driven through weak or jointed rock. Although ground conditions and support systems are often studied in detail, the effect of tunnel geometry on collapse behaviour is still not fully understood. This paper examines how different tunnel shapes influence collapse mechanisms using numerical modelling. Numerical analyses are carried out for circular, horseshoe, and D-shaped tunnels under varying overburden depths and rock mass quality conditions. Additional parametric studies are performed by changing joint orientation, groundwater pressure, and support conditions for each tunnel geometry. Collapse behaviour is evaluated by analysing stress distribution, development of plastic zones, deformation patterns, and failure modes obtained from the simulations. The results indicate that tunnel geometry has a noticeable influence on stress concentration and deformation, leading to different collapse patterns under similar ground conditions. A comparative assessment of tunnel shapes is presented to identify their relative stability. The study highlights the importance of considering tunnel geometry explicitly during design and provides useful insight for safer and more informed tunnel planning.