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Abstract As coal mining depth increases, there is a corresponding increase in both ground stress and gas pressure, leading to a higher incidence of coal and gas outburst accidents. To investigate the stress distribution law and gas release degree of the adjacent coal body within the goaf of the outburst coal seam, and to acquire an understanding of the impact range of the large mining face goaf on the stress of the coal seam, this study employed theoretical analysis and numerical simulation to analyze the impact and scope of the goaf on the adjacent coal body, and measured the gas content of the coal seam. The findings indicated that following the completion of mining on the working face, there was a redistribution of stress in the coal and rock layers within 40 m of the goaf, with the stress concentration phenomenon observed at a distance of 2.6 m from the goaf. Affected by the stress relief effect of mining, the stress, gas content, and other related factors have been studied in detail by researchers. Affected by the stress relief effect of mining, the stress, gas content, and gas pressure of the surrounding rock near the goaf in the coal seam are significantly reduced. The research results verify that tunneling along the goaf is an effective method to prevent coal and gas outbursts and improve stoping efficiency.

As coal mining depth increases, there is a corresponding increase in both ground stress and gas pressure, leading to a higher incidence of coal and gas outburst accidents. To investigate the stress distribution law and gas release degree of the adjacent coal body within the goaf of the outburst coal seam, and to acquire an understanding of the impact range of the large mining face goaf on the stress of the coal seam, this study employed theoretical analysis and numerical simulation to analyze the impact and scope of the goaf on the adjacent coal body, and measured the gas content of the coal seam. The findings indicated that following the completion of mining on the working face, there was a redistribution of stress in the coal and rock layers within 40 m of the goaf, with the stress concentration phenomenon observed at a distance of 2.6 m from the goaf. Affected by the stress relief effect of mining, the stress, gas content, and other related factors have been studied in detail by researchers. Affected by the stress relief effect of mining, the stress, gas content, and gas pressure of the surrounding rock near the goaf in the coal seam are significantly reduced. The research results verify that tunneling along the goaf is an effective method to prevent coal and gas outbursts and improve stoping efficiency. [ABSTRACT FROM AUTHOR]

Abstract Compared with the traditional “dynamic‐static” load rockburst induced by working face mining, a new typical disaster with concealment characteristics has appeared in deep thick coal seam roadways, namely, static creep rockburst, the occurrence mechanism of which remains unclear. Through the method of combining theory with practice, this paper elucidated the mechanical mechanism of static creep rockburst of deep thick coal seam roadways, along with the CT inversion of its rockburst risk. Next, by establishing the creep model and three‐dimensional creep formula under static conditions, it was observed that the main conditions for the unstable creep of deep thick coal seam roadway were high stress and thick coal seam. In addition, by analyzing the unstable creep failure process of surrounding rock in static roadways, it was found that the weakening of surrounding rock strength and stress relief were the reasons for starting rockburst and reducing impedance. The mechanical conditions of creep rockburst caused by stress superposition in weak areas of the roadway under static conditions were proposed, and the criterion of rockburst possibility was given. Finally, according to the characteristics of spontaneity and time delay of such a rockburst disaster, the static creep rockburst evaluation of thick coal seam roadway before mining was achieved by CT inversion, and the research conclusions were thoroughly verified.

Compared with the traditional "dynamic‐static" load rockburst induced by working face mining, a new typical disaster with concealment characteristics has appeared in deep thick coal seam roadways, namely, static creep rockburst, the occurrence mechanism of which remains unclear. Through the method of combining theory with practice, this paper elucidated the mechanical mechanism of static creep rockburst of deep thick coal seam roadways, along with the CT inversion of its rockburst risk. Next, by establishing the creep model and three‐dimensional creep formula under static conditions, it was observed that the main conditions for the unstable creep of deep thick coal seam roadway were high stress and thick coal seam. In addition, by analyzing the unstable creep failure process of surrounding rock in static roadways, it was found that the weakening of surrounding rock strength and stress relief were the reasons for starting rockburst and reducing impedance. The mechanical conditions of creep rockburst caused by stress superposition in weak areas of the roadway under static conditions were proposed, and the criterion of rockburst possibility was given. Finally, according to the characteristics of spontaneity and time delay of such a rockburst disaster, the static creep rockburst evaluation of thick coal seam roadway before mining was achieved by CT inversion, and the research conclusions were thoroughly verified. [ABSTRACT FROM AUTHOR]

Abstract Coal and gas outburst disasters are prone to occur within rock cross‐cut coal uncovering in deep underground coal mines. To reduce the risk of coal and gas burst under rock cross‐cut coal uncovering, a technique of permeability enhancement using hydraulic fracturing sand‐carrying is proposed. Field test was conducted using HF sand‐carrying approach, and the effect of permeability enhancement was investigated. The results show that the evolution of cracks has been subjected three stages: energy slowly increasing and crack initiation, damage localization of coal seam and gradually failure, and crack instability expansion and formation of a complex fracture network system. In addition, it is found that “water‐sand” type injection of high‐pressure fluid carried sand into HF cracks, which creates a support force on crack surface and prevents crack closure. A fully developed fracture network system with high flow conductivity capacity is created and thus increases gas permeability largely. Furthermore, a clearly increasing trend associated with the HF sand‐carrying is found for the treated coal seam area. The permeability coefficient is about 21.5‐30.5 times higher than that from the raw coal seam. A good prevention effect of coal and gas outburst is achieved using HF sand‐carrying method.

Coal and gas outburst disasters are prone to occur within rock cross‐cut coal uncovering in deep underground coal mines. To reduce the risk of coal and gas burst under rock cross‐cut coal uncovering, a technique of permeability enhancement using hydraulic fracturing sand‐carrying is proposed. Field test was conducted using HF sand‐carrying approach, and the effect of permeability enhancement was investigated. The results show that the evolution of cracks has been subjected three stages: energy slowly increasing and crack initiation, damage localization of coal seam and gradually failure, and crack instability expansion and formation of a complex fracture network system. In addition, it is found that "water‐sand" type injection of high‐pressure fluid carried sand into HF cracks, which creates a support force on crack surface and prevents crack closure. A fully developed fracture network system with high flow conductivity capacity is created and thus increases gas permeability largely. Furthermore, a clearly increasing trend associated with the HF sand‐carrying is found for the treated coal seam area. The permeability coefficient is about 21.5‐30.5 times higher than that from the raw coal seam. A good prevention effect of coal and gas outburst is achieved using HF sand‐carrying method. [ABSTRACT FROM AUTHOR]