English：

To explore the ventilation effect and gas migration characteristics in the process of blastingconstruction of a low⁃gas tunnel, based on the Tongjialiang Tunnel Project, the method of field monitoringand numerical simulation was used to systematically study the airflow organization form and gasconcentration spatial distribution law in the tunnel under the condition of forced ventilation. The resultsindicate that the gas concentration in the tunnel decreases rapidly with the increase in the distance fromthe tunnel face, then rises slightly, and finally tends to be stable. There are significant differences in gasconcentration at different spatial positions. The left corner area is the highest, followed by the tunnel axisposition, the right corner position, and the lowest concentration is in the central area of the ventilationpipe. The numerical simulation results indicate that under the condition of forced ventilation, the airflowstructure of the tunnel can be divided into three categories: jet zone, recirculation zone, and vortex zone.When the ventilation pipe is arranged on the upper right of the tunnel, the low concentration area of gasis mainly distributed near the air duct, while the high concentration area is concentrated in the left lowerarch waist area far away from the side of the air duct. The diameter of the air duct, the ventilation airvolume, and the distance between the outlet of the air duct and the face of the tunnel all have asignificant impact on the average gas concentration on the face of the tunnel. The degree of influence,from large to small, is the diameter of the air duct, the ventilation air volume, and the distance betweenthe outlet of the air duct and the face of the tunnel.