## 3 Analysis of Results and Discussion
### Analysis of the Influence of the Gas Baffle on Gas Leakage Monitoring
#### 3.1.1 Leak Response Time Effect Analysis
In other words, under normal ventilation conditions, if the gas baffle is set close to the monitor, there is a possibility of weakening the monitoring effect. Figure 4: CH\({}_{4}\) concentration at detection points versus time under unventilated conditions. (3) Effect of the baffles at different heights of the gas baffle  
According to the requirements of the relevant standards and specifications for the installation of obstructions and air intake and exhaust in the tunnel cabin, and taking into account the usual operation and maintenance and personnel activities, [PERSON] et al. provided a range of 0.4, 0.5, and 0.6 m for the height of the air baffle. In order to investigate whether the height of the air baffle has an effect on the monitoring effect, the height of the air baffle was adjusted to 0.3 m, 0.5 m, and 0.7 m in order to simulate and analyse the situation with a ventilation wind speed of 0 m/s and a leakage velocity of 50 m/s. The variation of CH\({}_{4}\) concentration at the monitoring point with time for different baffle heights was obtained, as shown in Figure 6.  
As can be seen from Figure 6, the height of the gas baffle is adjusted from 0.3 m to 0.7 m, and the curve shows a slight difference as the height of the gas baffle increases, with no significant change in alarm response time or peak CH4 concentration. Combined with the height requirement of the top obstacle in the Zhengzhou Xuwei gas chamber (\(\leq\)0.5 m) and the simulation calculation results, it can be seen that after the height of the gas baffle reaches 0.5 m, continuing to increase the height does not improve the effect significantly,  
Figure 5: CH\({}_{4}\) concentration versus time at monitoring points under normal ventilation conditions. Figure 6: Effect of air baffles at different heights. but will increase the cost, so it is recommended that the height of the gas baffle should be set no greater than 0.5 m.  
(4) Effect of the baffles at different leak locations  
The location of the leakage source can always be considered to be between two monitors. Therefore, different leakage positions can be regarded as different spacings between the leakage hole and monitoring points. In order to study the different spacings between the leakage hole and the monitor and increase the influence of the baffle plate on the monitoring effect, the horizontal distance between the leakage hole and the downstream monitor was set as 5.0 m, 7.5 m, and 10.0 m successively. A ventilation wind speed of 0 m/s, leakage speed of 50 m/s, and baffle height of 0.5 m were selected for the calculation analysis. At different leakage locations, the concentration of CH\({}_{4}\) at the monitoring point before and after adding a gas baffle varies with time, as shown in Figure 7.  
As can be seen from Figure 7, in the section formed by two monitors without ventilation, the greater the horizontal distance between the leakage hole and the downstream monitor, the more obvious the monitoring effect improvement. Combined with the actual engineering, the monitor with the closest horizontal distance is usually the first to alarm under the condition of ensuring the normal operation of the monitor. [PERSON] et al. suggested that combustible gas detectors should be set on both sides of each baffle, and the spacing between two adjacent baffle plates should be set as 50 m. In accordance with the usual practice of setting an interval of about 15 m for combustible gas monitors in the gas compartment of the integrated corridor, at least 13 monitors will be arranged in the corridor section with a length of 200 m. By adopting the new layout scheme, the number of monitors can be reduced by 38%, thus reducing the project cost.