Controlling effect of tectonic stress field on coal and gas outburst

Abstract

To investigate the controlling effect of tectonic stress field on coal and gas outburst, the gas geology, tectonophysics and rock mechanics methods were applied to analyze the influences of tectonic stress field on tectonic coal, in-situ stress and coal seam gas. Based on the case of coal and gas outburst, the effect of tectonic stress field on the distribution, type and strength of coal and gas outburst was studied. The mechanism and action forms of coal and gas outburst controlled by tectonic stress field were revealed. Results show that the tectonic stress field controls the characteristics of coal body structure distribution, coal body structure type and coal body strength. The compressive tectonic stress field is the main form of stress action for the tectonic coal formation, and the compresso-shear fault zone and interlayer-gliding fracture zone of fold form the development area of tectonic coal. The larger the tectonic stress field intensity is, the higher the fracturing degree of the coal body is, and the lower the coal body intensity is. The tectonic stress field controls the type, level and direction of the in-situ stress field. The region dominated by the intensive tectonic stress field belongs to the dynamic stress field and is at the high in-situ stress environment, and the direction of the tectonic stress field is the direction of the maximum horizontal principal stress of in-situ stress. The tectonic stress field affects the coal seam gas enrichment degree. Under the action of the strong tectonic stress field, the coal seam permeability is lower, the gas content and gas pressure are higher, and the compresso-shear structure zone forms the gas enrichment area. Under the action of the multistage tectonic stress filed, the distribution of tectonic coal, in-situ stress and gas of coal seam has the regional characteristic, which controls the partitioning and zonal distribution of coal and gas outburst. The horizontal compressional stress caused by the tectonic stress field controls the coal and gas outburst type dominated by coal and gas press-out. With the increase of the angle between the direction of the maximum horizontal principal stress and the axial direction of the roadway, the stress concentration factor increases and the coal and gas outburst intensity increases gradually. With the increase of maximum horizontal principal stress, the elastic deformation energy of coal and rock mass and gas expansion energy increase and the coal and gas outburst intensity increases. The research results provide a theoretical basis for predicting and preventing coal and gas outburst.

Keywords

• tectonic stress field
• coal and gas outburst
• tectonophysics
• outburst pattern
• outburst mechanism