Abstract The gas emission from non-coal measure strata such as metamorphic sand slate and phyllite has the characteristics of random and uneven distribution. Taking Miyaluo No.3 tunnel on Wenchuan-Maerkang highway as the engineering background, this paper analyzes the geological background, gas geological characteristics and measured gas data regarding the tunnel, studies the mechanism and prevention measures of gas outburst in this kind of stratum. The study shows that the carbonaceous component in the sand slate has a certain capacity of hydrocarbon generation; via long and through fissures and fault fracture zones the gas is led from deeper stratum to shallow stratum; the gas is stored in densely developed joint zones, secondary bend fold zones and secondary fault fracture zones, where it is distributed in lenticular and bead-like pockets. If construction uncovers the closed cover around the lenticular gas and water storage structure, the broken rock, water and gas within the structure would suddenly gush out under the effect of water pressure and gas pressure, forming an outburst disaster. This type of gas has complex causal mechanisms and is difficult to predict, so comprehensive measures such as advance discharge, dilution and monitoring should be taken.
Abstract：
The gas emission from non-coal measure strata such as metamorphic sand slate and phyllite has the characteristics of random and uneven distribution. Taking Miyaluo No.3 tunnel on Wenchuan-Maerkang highway as the engineering background, this paper analyzes the geological background, gas geological characteristics and measured gas data regarding the tunnel, studies the mechanism and prevention measures of gas outburst in this kind of stratum. The study shows that the carbonaceous component in the sand slate has a certain capacity of hydrocarbon generation; via long and through fissures and fault fracture zones the gas is led from deeper stratum to shallow stratum; the gas is stored in densely developed joint zones, secondary bend fold zones and secondary fault fracture zones, where it is distributed in lenticular and bead-like pockets. If construction uncovers the closed cover around the lenticular gas and water storage structure, the broken rock, water and gas within the structure would suddenly gush out under the effect of water pressure and gas pressure, forming an outburst disaster. This type of gas has complex causal mechanisms and is difficult to predict, so comprehensive measures such as advance discharge, dilution and monitoring should be taken.
DU Yi CHENG Qiang
.Study and Analysis of the Mechanism of Gas Emission (Outburst) in Miyaluo No.3 Tunnel on Wenchuan-Maerkang Highway[J] MODERN TUNNELLING TECHNOLOGY, 2021,V58(4): 203-209
2021, Vol. 58 