Calculation of water storage space and changes in underground coal mine reservoirs

Abstract

In view of the limited limited water storage space and unstable structure in traditional caving mining, and the invisibility of goaf leads to the difficulty of accurate calculation of water storage space, this paper proposes a comprehensive technical method for the digitization of spatial form of coal mine goaf. Combined with goaf detection technology, a three-dimensional digital model of water storage space is constructed to reduce the difficulty of calculating water storage space in traditional caving mining, so as to accurately obtain the three-dimensional form, spatial position and actual boundary of goaf. Based on the geological conditions of the goaf in Halagou Coal Mine, the similar material simulation combined with Red-Green-Blue (RGB) digital image threshold segmentation method was used to quantitatively characterize the water storage space of the underground reservoir in the goaf. The grading loading compaction-seepage test of broken gangue was carried out to study the evolution law of loose coefficient and effective porosity. The results show that the water storage space of overlying strata experiences four continuous stages : fracture development, bed separation expansion, fracture closure and compaction stability. The effective porosity in the bed separation expansion stage reaches a maximum of about 30%, and stabilizes to about 20% after compaction, indicating that the effective water storage space accounts for about 20% of the mining space, which provides a quantitative basis for the estimation of water storage capacity of underground reservoirs in goaf.