Gezhenpu tunnel is the vital construction project in Liaoning Province

its geoligical condition is complex

and there is cataclastic section exists

the conventional method can not reflect the mechanical behavior. Aiming at above problem

according to without supporting

primary supporting and secondary supporting

geotechnical engineering software FLAC3D is adopted; and large scale numerical grid is constructed

the 3D numerical simulation for dynamic construction process is carried out with 4 meters each step and upper and lower steps. Through simulating and analyzing the stress field

displacement field and plastic zones

the complex mechanical behaviors of excavation and supporting are analyzed. Calculation result shows that the displacement is in accordance with monitoring data

the original secondary supporting scheme can guarantee the stability of surrounding rock.The result of numerical simulation has guiding meaning to the tunnel construction.