Effects of geo-stress on the dynamic response of multi-physical field parameters during coal and gas outbursts under true triaxial stress

Abstract

With the increase of the mining depth in coal mining operations, more coal and gas outburst (CGO) disasters are likely occur due to the increase in geo-stress. The limitations of conventional experimental methods prevent the observation of multi-physics parameters and dynamic effects during CGO. In this work, a customized coal mine dynamic disaster test system was used to analyze the evolution of multi-physics parameters such as gas pressure, temperature, and geo-stress during CGO. The influences of geo-stress on the energy sources of CGO were discussed and the response characteristics of the coal-gas flow in the roadway during the CGO were analyzed. Results show that during the CGO process, an increase in the geo-stress will decrease the gas pressure and rate of the pressure drop. The rate of geo-stress change gradually increases with an increase in the initial stress, and the peak impact force of the coal-gas flow increases with increasing geo-stress. The elastic strain energy released during CGO also increases with increasing geo-stress, however, it is less valuable than gas expansion energy. The contribution of geo-stress to the CGO depends on its influence on the gas expansion energy. Coal seam temperature variations are mainly manifested in the stress relief and abutment stress zones, and the flow velocity of CGO coal demonstrates alternating deceleration and acceleration cycles. Additionally, the obtained distribution characteristics of CGO coal exhibit log-normal patterns. These findings can help further understand the CGO mechanism and provide a reference for passive disaster reduction measures after outbursts.