Numerical simulation research on fire risk in a super long river-crossing subway tunnel

In recent years, with the gradually increasing number of river-crossing tunnels, the risk of tunnel fire continues to rise, so it is necessary to research the control effect of fire smoke for different kinds of tunnel structure and the ventilation and smoke exhaustion system. The FDS software was used to simulate the scene of fire at different slope segment of Nanjing Metro Line 10 in the case of single-way and two-way structure, and the variation of the temperature, concentration of CO, visibility and the height of smoke layer were analyzed [1]. Research results show that: in terms of the temperature, concentration of CO and visibility in the -7.5 tunnel, single-way tunnel structure has a certain advantage, however, for the +8.9 tunnel, the two-way tunnel is lower than single-way tunnel in connection with the risk parameter values. And in general, fire risk in the positive (+8.9) slope segment is less than that in the negative (-7.5) slope segment. By combining the structure of the two tunnels, in the actual design and application process, the choice of two-way scheme is better. impact and economic loss. In view of the different tunnel structures, the impact of the traditional ventilation mode on the tunnel temperature was studied by Vladimir Maslak [2]. The effect of the exhaust duct size and the position of the fire source in tunnels was studied by R. Harish [3]. This paper mainly uses FDS software to carry out a series of research on ventilation and smoke exhaust system of Nanjing Metro Line 10, and through the comparison of different subway tunnels, finally determine the suitable design structure. Nanjing Metro Line 10 tunnel across the river is from the Riverside Road station to Jiangxinzhou station, full length of 3850m, is a super long interval, divided into 1130m, 740m, 1030m, 950m four gradient tunnel, corresponding slope is -28, -7.5, +8.9, +28 [4], marking A, B, C, D. This article considers -7.5 and +8.9 two high-risk tunnels, schematic diagram is shown in Fig. 1. According to existing subway tunnel structure, this paper’s main structure of tunnel was divided into two types: single-hole double-line (two-way) and single-hole single-track (single-way) structure.