Based on a visco-elastoplastic model considering the feature of water degradation effect of rock

its finite difference scheme is presented. Through program development for the model by C++ language

the FLAC3D dynamic link library file is obtained. To test the model effectiveness

it is shown that the model program can better simulate the instantaneous elastic deformation

attenuation creep

creep constant

water degradation and plastic deformation characteristics of rock. With the numerical calculation for an on-site tunnel geological model by the visco-elastoplastic model program

it is shown that the vault settlement

convergence and uplift deformation increase with the growth of moisture content

and the time that surrounding rock remains stable is shortened. Uplift displacement in saturated state is twice of that in natural moisture state; and the time that surrounding rock remains stable in saturated state is less than that in natural moisture state for about 40 days; so reasonable construction time for the second supporting is also greatly shortened. The calculation results are consistent with the measuring results in the tunnel site

which can explain the generation mechanism of large deformation disaster effectively. Both stability of rock-support system and reasonable time for the second supporting can be well predicted by the visco-elastoplastic model program presented above.