Numerical Experiment for Support Effect of Umbrella Arch in Tunnel

Umbrella arch is often used as pre-support for shallow tunnel and poor surrounding rock. To evaluate the support effect quantitatively, 12 cases by numerical analysis were used to study the effect of cover depth and condition of surrounding rock on the support effect of umbrella arch. Load percentage of umbrella arch was proposed to evaluate the effectiveness of umbrella arch. The umbrella arch could not work when the percentage was less than 50%. When the surrounding rock was poor and the shallower the cover depth, the better the support effect.