Determination of roof horizontal long drilling hole layout layer by dynamic porosity evolution law of coal and rock

Abstract

The key to the layout of the roof horizontal long drilling hole is to accurately locate the range of gas-conducting fracture zone. In this paper, the discrete element method (DEM) is firstly adopted to quantitatively simulate the porosity distribution in goaf from a microscopic perspective, with the 6306 working face of the Tangkou coal mine as an engineering example. Then, the three-dimensional porosity distribution data is extracted and converted into a two-dimensional array form, which was verified by the mathematical model established by previous work. After that, combining the DEM data and mathematical model result, user-defined function (UDF) codes are written and imported into computational fluid dynamics (CFD) software to simulate the gas distribution in the goaf before and after the drilling of the working face. The results show that the gas in goaf is mainly distributed in the upper position after drilling, and the proportion of gas in the bottom position is largely reduced. The boreholes arrangement in the gas-guiding fissure zone is reasonable effectively reducing the gas concentration in goaf.