Evaluation of the Risk of Water Gushing（Inrush）in Aquifer of Coal Seam Roof Based on "Three Diagram Method" – a Case Study in Hu Jiahe Coal Mine,china

Abstract Coal seam roof inrush phenomenon is common in Jurassic coalfield in China. In order to evaluate accurately the risk of coal seam roof water inrush (CSRWI) it needs to analyze the degree of water rich degree and crack height of strata aquifer. Based on the combined weight-TOPSIS theory, this paper intends to adopt the 8 factors of aquifer thickness, lithological structure index, core adoption rate and permeability coefficient, and TDS from the three aspects of aquifer lithology, hydrology and hydrochemical characteristics. As an evaluation index of the water richness of the aquifer in the Luohe Formation, By using the method of GI method and independent weight method subjective and objective weights influencing aquifer water rich control factors are determined and then weights are coupled by differential maximization theory.Based on GIS spatial analysis technology, an evaluation model of aquifer water rich in coal seam roof aquifer was established and verified by field measured hydrological pore data.Through empirical value calculation of coal seam roof crack height and further refinement of hydraulic fracture zone spread across aquifer floor and combined with aquifer degree of water enrichment and roof cracking degree to carry out comprehensive evaluation of the risk of CSRWI. The most important factors affecting the degree of water enrichment of aquifers are lithological structure index and permeability coefficient, followed by TDS. Compared with water-rich index method, the water-rich degree of aquifer can be effectively determined based on combination weight and TOPSIS method. Moreover, subdivision of roof crack degree indicates that the development height of hydraulic fracture zone in research area is disturbed by aquifer actual disturbance; Risk assessment results indicate that high risk of water inrush lies in southwest side of research area and prevention should be strengthened when mining. This study provides a new idea for evaluating risk zoning of coal seam roof gushing (inrush) water in coal mines of Binchang.