Abstract Carbonaceous phyllite is a kind of metamorphic rock widely distributed in Southwestern China. Multiple abnormal gas emission accidents have occurred in the tunnel excavatrion through the carbonaceous phyllite stratum,seriously threatening the safety of construction personnel and causing a sharp increase in construction cost. Based on the Zhegushan Tunnel on the Wenchuan-Maerkang Expressway, the carbonaceous phyllite stratum is tested and analyzed in respect of the gas composition, carbon isotope test, rock mass maturity and adsorption capacity, and gas pressure. The results show that the carbonaceous phyllite is in the mature-highly mature stage and has the ability to generate organic hydrocarbons. The maximum gas adsorption capacity of the rock mass is 0.59-0.73 mmol/g, with low gas adsorption amount and underdeveloped migration channels. The safety risk caused by gas desorption is not high. In areas with complex geological structures, the gas distribution in the carbonaceous phyllite stratum is uneven, and a large amount of pressurized gas accumulates locally, resulting in a high hazard degree. During construction, the measures shall be taken to mainly prevent gas outburst accidents caused by gases in the areas with complex geological structures and air bags formed by high-pressure enclosed rock mass.
Abstract：
Carbonaceous phyllite is a kind of metamorphic rock widely distributed in Southwestern China. Multiple abnormal gas emission accidents have occurred in the tunnel excavatrion through the carbonaceous phyllite stratum,seriously threatening the safety of construction personnel and causing a sharp increase in construction cost. Based on the Zhegushan Tunnel on the Wenchuan-Maerkang Expressway, the carbonaceous phyllite stratum is tested and analyzed in respect of the gas composition, carbon isotope test, rock mass maturity and adsorption capacity, and gas pressure. The results show that the carbonaceous phyllite is in the mature-highly mature stage and has the ability to generate organic hydrocarbons. The maximum gas adsorption capacity of the rock mass is 0.59-0.73 mmol/g, with low gas adsorption amount and underdeveloped migration channels. The safety risk caused by gas desorption is not high. In areas with complex geological structures, the gas distribution in the carbonaceous phyllite stratum is uneven, and a large amount of pressurized gas accumulates locally, resulting in a high hazard degree. During construction, the measures shall be taken to mainly prevent gas outburst accidents caused by gases in the areas with complex geological structures and air bags formed by high-pressure enclosed rock mass.
LIU Jiamin1 YANG Feng2 LI Xiaohong2 MA Hongsheng2
.Study on Occurrence Characteristics and Risk Prevention Measures of Gas in Non-coal Strata in Zhegushan Tunnel on Wenchuan-Maerkang Expressway[J] MODERN TUNNELLING TECHNOLOGY, 2023,V60(4): 172-177
2023, Vol. 60 