Monitoring and modelling of gas dynamics in multi-level longwall top coal caving of ultra-thick coal seams, part I: Borehole measurements and a conceptual model for gas emission zones

• The in situ pressure regimes and gas composition at different mining levels of an ultra-thick coal seam were monitored.
• Gas pressure and composition response to face advance of the coal seam around a LTCC extraction have been evaluated.
• A conceptual gas emission model for a longwall top coal caving panel was developed.

The application of multi-level longwall top coal caving mining method in ultra-thick coal seams generally yields a much higher productivity and is more efficient in comparison to a mechanised single-slice longwall panel. However, the greater productivity achieved by this mining method may further exacerbate the gas emission problems often faced in longwall mining. In order to establish a thorough understanding of gas pressure regimes, and gas emission patterns around a producing multi-level longwall top coal caving face, a suite of in-situ measurements on seam gas pressure, gas composition, and ventilation environment was conducted at Coal Mine Velenje in Slovenia. This paper focuses on the analysis of these field observations which helped develop a conceptual gas emission model for multi-level longwall top coal caving mining of ultra-thick coal seams. It has been found that, at Coal Mine Velenje, the coal zone within 40 m ahead of the face can significantly contribute to the overall district gas emission. In addition, floor coal and roof goaf may both play a major role towards the total gas emitted during mining.