The physical model test of a tunnel is made on the triaxial model-test machine. The whole failure process is observed by applying full inner-spy photograph technology; with it the deformation and crack extension of key parts are studied. By using the strain measure technology

the strains of key parts of the surrounding rock are measured; according to this

the variability of the stresses of surrounding rock is studied. The measured values of the main physical and mechanical indices of the model material are closed to the theoretical values. Based on the mechanical property of the model material

the Mohr-Coulomb criterion with tension cut-off strain-softening model is established. The numerical simulation are worked with the same boundary condition as the model test; according to this

the plastic zone and the stress field of the surrounding rock are studied. We compare the failure process and the variation of stress of the surrounding rock of the model test with the numerical simulation and draw the conclusion that the two processes coincide with each other.