Tunnel construction ventilation scheme (design, calculation, etc.)
XXX tunnel is 8836m long, which is the longest tunnel of XX railway. The tunnel is located in Zhenxiong, Yunnan Province. The stratum where the tunnel crosses is mainly Permian, Silurian and Ordovician argillaceous limestone, limestone, sandstone shale with coal seam and dolomite, and gypsum and salt rock are contained locally. Unfavorable geology mainly includes karst, coal seam gas, dangerous rock fall, fault and fracture zone. The tunnel is located within the horizontal circulation zone of karst water. It is predicted that the water inflow of the tunnel in normal period is 34672m3/d, and the maximum water inflow in rainy period is 80935m3/d. The whole tunnel is a low gas tunnel, and the initial risk level of tunnel risk assessment is "height". This section is responsible for the construction of 3025m exit. The unfavorable geology of XXX tunnel mainly includes karst, water and mud inrush, landslide and harmful gas. The main risks of the tunnel are collapse and falling, water and mud gushing and harmful gas overflow. The entrance of XX Tunnel is near XX Township, and the exit is near the pass. The entrance mileage is D3K321+668, and the exit mileage is D3K326+509, with a total length of 4841m, including 810m of Grade II surrounding rock; Class III surrounding rock 505m; Class IV surrounding rock 2192m; Grade V surrounding rock is 1165m. Except the 32m flat slope at the entrance section, the rest sections are 16 ‰ downhill. The unfavorable geology of XX tunnel is mainly karst and high gas. The main risks of the tunnel are collapse and block falling, water and mud gushing and gas outburst. In order to meet the construction period, solve the problems of ventilation, construction drainage, mucking, drainage and disaster prevention and rescue during the operation of the coal seam gas karst tunnel, and combine the terrain and geological conditions, the tunnel is equipped with the configuration scheme of "1 horizontal tunnel". At D3K325+300, a transverse tunnel is set on the left side of the line in the forward direction. The intersection angle between the transverse tunnel and the plane of the line in the direction of large mileage is 50 °. The length of the transverse tunnel is 574m, and the gradient of the tunnel body is 0.3%. The tunnel is divided into three work areas: main tunnel inlet, main tunnel outlet and cross tunnel. Forced ventilation and trackless transportation are adopted in the tunnel entrance and exit work areas; The cross tunnel work area is a high gas work area, which adopts forced ventilation and rail transportation.