Water Inrush Risk Assessment of Coal Floor After CBM Development Based on the Fractal-AHP-Vulnerlability Index Method

Abstract

The water inrush risk assessment of coal floor after coalbed methane (CBM) development is very important in the theoretical and practical study of safe coal mining. In this study, Chengzhuang coal mine is used as an example to evaluate the water inrush risk of the Ordovician aquifer in coal seam No.15 after the CBM development using the fractal-AHP-vulnerability index (VI) method. Using rock mechanics and geomechanics, a theoretical analysis of water inrush from the coal floor after CBM development is conducted, and two main control factors are added: minimum horizontal principal stress and rock fracture pressure of the hydrologic barrier. By fractal theory, instead of density, length, width and fault distance, the fractal dimension is used to quantify fault. Using the AHP-VI method, the water inrush risk of coal floor after CBM development is analyzed. The results show that there are 8 types of discrimination conditions and 6 main control factors for floor water inrush after CBM development. The fractal-AHP-VI method is more accurate than the traditional AHP-VI method. This method has reference value for the water inrush risk assessment of coal floor after CBM development.