GAS EVALUATION OF TONGLUO MOUNTAIN TUNNEL ON CHENGDU-DAZHOU-WANZHOU RAILWAY

The Tongluo Mountain tunnel of the Chengdu-Dazhou-Wanzhou Railway will pass through some areas with complex structures, and be going to suffer damage from coal seam gas and natural gas at the same time. For the simplicity, we call this kind of tunnel as the coal-and-gas tunnel. The methods which researchers often used to calculate the absolute gas emission rate, can no longer effectively evaluate the gas level of the coal-and-gas tunnel. We first used the experimental data of coal samples and the gas concentration data detected in the forecasting holes to calculate the absolute gas emission rate, and evaluated the gas level of the Tongluo Mountain tunnel by the conventional methods. Following that, we summarized the geological information and engineering data such as structure, lithology, and groundwater exposure of the tunnel site, etc., and used the fuzzy comprehensive evaluation method to evaluate the gas level of the tunnel again. By comparing with some of the existing similar tunnels in the area, we verified the effectiveness of the fuzzy comprehensive evaluation method. The results show that it is inadequate to evaluate the gas level of the coal-and-gas tunnel by calculating the absolute gas emission rate. The evaluation result of fuzzy comprehensive evaluation method is more reliable, because it can take the influence of a variety of comprehensive factors into consideration and evaluate the gas level of each section of the tunnel. The Tongluo Mountain tunnel is rated as a high-gas tunnel. Among the 9 sections of work area with gas, there are 3 high-gas sections and 2 low-gas sections. The research provides a new method to evaluate the gas level of coal-and-gas tunnels under the influence of multiple factors.