Investigation of the Effects of Tunnel Cross-Section Geometry on the Performance of the Lining Structure Subjected to External Blast Loading

In this study, the effects of tunnel cross-section geometry and relative position of the explosives on the performance of the lining structure subjected to external blast loading have been investigated using finite difference method. The crosssection geometry of the modeled tunnels considered as rectangular, horseshoe and semicircle and designed based on the regulation proposed in the Iranian code No. 161(Geometric Design of Roads). To evaluate the effect of the explosive relative distance, the blast center on the ground surface was assumed at different distances relative to the center of tunnel crown. The results indicated that under the surface blast, the performance of the horseshoe crosssection tunnels was more suitable than the others. Furthermore, for the all cross-section types, the increase of blast center distance relative to the center of tunnel crown resulted in a reduction in the maximum vertical displacement of the center of tunnel crown. This was observed together with an initial increase and then reduction in the maximum values of axial force, bending moment and normal stress in the lining of tunnels.