<p>The impact of tunnel shape on the soil arching effect warrants further investigation. In this study, numerical trapdoor models with different tunnel shapes were simulated via the discrete element method, calibrated against previous experimental data.&#xa0;The results showed that for the shadowing effect above tunnels, the rectangular tunnel induced the most substantial shadowing zone, while the circular tunnel produced the smallest. Additionally, the circular tunnel model exhibited the highest minimum soil arching ratio, whereas the rectangular tunnel model had the lowest, indicating a more pronounced soil arching effect in rectangular tunnels. The rectangular tunnel model showed the lowest ultimate soil arching ratio and load recovery index, indicating the greatest potential for maintaining the soil arching effect. In Part-L1, the stress ratio sharply decreased with small trapdoor displacements before stabilizing. In contrast, Part-L2 and Part-L3 both exhibited increasing trends, with Part-L2 showing a more pronounced rise than Part-L3. The Horseshoe1 tunnel exhibited minimal distribution of weak force chains and limited variation in strong force chains, whereas the rectangular tunnel displayed the most extensive dispersion of weak force chains and higher fluctuation in strong force chains. The increase in trapdoor displacement not only amplified anisotropy but also triggered instability in the principal anisotropy directions.</p>