In order to investigate the effect of cracking orientation on the stability of tunnel surrounding rocks

experimental and numerical studies were implemented. In the experiment

cement mortar models with different cracking orientations were made and loaded after cured room temperature for 30 days. In the numerical simulation

the concrete damaged plasticity was adopted. The stresses at the points around the tunnel and the stress intensity factor of crack tips were calculated; the results were in good agreement with the experimental results. The results show that cracks in the spandrel can reduce the stability and strength of tunnels

and induce a great stress concentration at the crack tip and the sidewall of tunnels; but this phenomenon exist in differences due to the angle between cracks and sidewalls. When =60° and =130?

cracks produce the most serious effect on the stability and strength of tunnels; and the peak of damage stress are only 40.9% and 41.8% of that of tunnels without cracks.