Effects of coal seam dip angle on the outburst in coal roadway excavation
Abstract The prevention and forecast of coal and gas outburst has always been one of the key issues in coal mining safety. By simulating the process of tunneling in coal seam with different dip angle through FLAC3D software, the dangerous zone in which outburst may occur and the probability of outburst near the working face were predicted through the distribution of stress, displacement and plastic zone. Then we discussed the size of unstable area in the surrounding rock through the distribution of stress and the variation curve of the displacement on the roadway wall. The results show that, with an increase of the coal seam dip angle, the risk of outburst in the working face rises gradually. And the dangerous areas in which may outburst occur moves to the upper part of coal seam. The size of unstable area in the surrounding rock increases with the increase of coal seam dip angle.
The relationship between economic development and environmental pollution has been widely studied in the context of the environmental Kuznets curve. This study applies the three-dimension framework of density, division, and distance proposed by the World Bank to identify the spatial heterogeneity of development and pollution in urban China. An inverted U relationship is detected between density and industrial SO2 emission, while a cubic relationship is found between density and industrial SO2/soot emission intensity. The statistical significance of division indicates that the pollution haven hypothesis holds in the western region and cities in the periphery. The environmental implication of distance is that the industrial pollution is largely concentrated in the national and regional cores.