Water-richness evaluation of Luohe Formation aquifer above coal seam based on combination weighting method

Hetaoyu well field has large production capacity and stable distribution of coal seam, The thick sandstone aquifer of Luohe Formation in the roof of coal seam is the main water-filling aquifer which will result in coal seam roof water damage and threatening the safety of mine production with the deepening of mining degree when the water-conducting fissure zone leads to the water-rich area of the overlying aquife. It is necessary for the safety mining of coal mine to find out the law of water-rich distribution of aquifer, because water richness evaluation of coal seam roof aquifer is the basis of water hazard prevention and control. In order to evaluate the water richness of Luohe Formation aquifer in the first mining area of the Hetaoyu well field, six indexes including aquifer thickness, collecting rate of drill core, thickness ratio of brittle-plasticity, washing liquid consumption, permeability coefficient, unit water inflow were selected as evaluation factors by analyzing borehole data and other well field data in the study area. Combination Weighting Method is used to carry out the index weight comprehensively based on Analytic Hierarchy Process (AHP) and CRITIC method, and the comprehensive weights of each index were 0.1707, 0.2078, 0.0976, 0.1171, 0.1465 and 0.2603, respectively. Using the FDAHP-Independent weight coefficient method, the weights of the four main controlling factors, such as aquifer thickness, core extraction rate, thickness ratio of brittle plastic rock and wash fluid consumption, are 0.1675, 0.312, 0.2575 and 0.263, respectively. A method of aquifer water-richness evaluation index model based on the combination weighting method was proposed, and zonation of water-richness zoning was made for seam roof Luohe Formation aquifer. The results show that the water richness distribution of the Luohe Formation aquifer in the roof of coal seam in the first mining area of Hetaoyu is uneven, which is obviously different from the distribution of each single index. The relatively weak and relatively weak water-rich areas are located in the eastern part of the study area, the middle part has medium water-rich water, and the strong water-rich areas are located in the central and western parts of the study area respectively. There are large areas of relatively strong water-richness in the central and western areas. It is necessary to pay attention to the strong water-richness in the western areas and local strong water richness points and do well in water exploration and release in advance.