Abstract
To analyze the effect of small faults in the working face on coal and gas outbursts, the coal and gas outburst accident in the 21431 working face was studied with the 3DEC numerical simulation method, and the main research contents were the change laws of both stresses at the small fault and the overburden strata movement rate in the small fault zone of which the drop height and the strike were designed into different groups. The results show that the risk of small fault slip increases with the advancing working face. In addition, there is a positive correlation between the risk and the small fault throw. The movement rate of overburden strata in the small fault zone increases along with the rising of the small fault throw, which increases the energy transferred to the coal seam from the surrounding rock under the effect of the small fault. Hence, the effect of small faults on the working face on coal and gas outbursts was positively correlated with the small fault throw. Under the influence of a small fault strike, the closer it is to the small fault along the dip distance at the same working face, the greater the risk will be of a coal and gas outburst. And the bigger the small fault strike is, the greater is the stress concentration degree in front of the working face and the more the elastic energy is stored and the greater is the possibility of an outburst. The paper analyzes the influence of small faults on coal and gas outbursts in the working face, which has reference significance for the prediction and prevention of coal and gas outburst disaster in the working face.
Highlights
In the production process of coal mines, the small fault is one of the major geological problems that have troubled mine production for a very long time
Nearly 80% of coal and gas outburst accidents are caused by small faults [5, 6], and these outburst accidents mostly occurred at coal roadway heading faces, followed by open-off cut, raise and dip, uncovering coal seam in the crosscut, mining face, and rock roadway heading face [7, 8]
Liu et al [19] established a mechanical analysis model of the expansion and evolution of the plastic zone in front of the driving face by numerical simulation method, analyzed the characteristics of the expansion and evolution of the plastic zone in front of the driving face, and discussed the physical and mechanical process and basic conditions of the development of coal and gas explosion caused by the evolution of the plastic zone
Summary
In the production process of coal mines, the small fault is one of the major geological problems that have troubled mine production for a very long time. Considering the difficulty in accurately identifying small faults [39, 40] (faults with a drop less than 5 meters) and the low gas content of coal seams in the mining area after gas drainage, it is difficult to let the coal and gas outburst accidents happen in the mining face [41]. The 3DEC three-dimensional discrete element numerical simulation method is used to analyze the control effect of different drops and different trends on the coal and gas outburst in the mining face during the coal seam mining process, in order to improve the effectiveness and pertinence of the mining face antiburst measures under the influence of small faults
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