The Effect of Opening Shapes on the Stability of Underground Tunnels: A Finite Element Analysis

Tunnel construction and development has long been an important component of smart cities and modern sustainable development projects around the world. Despite major advances in tunneling technologies, tunneling in rocks remains one of the most mammoth tasks for a geotechnical engineer to complete. Nowadays, all new complex and significant structures are designed and analyzed through finite element techniques. In the present study, numerical simulations have been carried out using the finite element code ABAQUS. Around the tunnel, a specified region of rock mass has been discretized into about 34000 elements. The Continuum Three Dimensional Eight Nodded Reduced integrated (C3D8R) elements were used to model the Tunnel. The effect of the shape of tunnel opening has been studied in three dimensional models using the Elastic Approach Solution Technique. A circular, oval, horse-shoe and square opening of a tunnel have been analyzed. In the current investigation, the behavior of flat head tunnels was also taken into account for comparison purposes. The crown of a flat head and round tubes of equivalent dimensions have shown the most deformation. On the other side, the oval shape has been found to have the fewest deformations at the crown of the opening. Furthermore, the horse-shoe opening, which is the most commonly used tunnel opening shape, has somewhat higher distortion than the oval opening.