Risk Assessment Of Water Inrush From Coal Seam Floor Under Pressure Based On Multiple Methods

Water inrush from coal floor is one of the urgent problems to be solved in coal mining.In order to study the danger of water inrush from coal floor in No.2,No.10 and No.12 mines of Pingdingshan Coalfield,the fractal theory is used to quantify the complexity of faults.The water pressure of the confined aquifer,the water richness of the aquifer,the thickness of the coal seam,the thickness of the aquifer and the complexity of the fault together constitute evaluation factors.According to the variable weight theory,the variable weight of each evaluation index in the study area is calculated.The matter-element extension model,fuzzy variable set,catastrophe theory and fuzzy comprehensive evaluation model are constructed respectively to evaluate the risk of water inrush from the coal seam floor of No.2 mine,No.10 mine and No.12 mine.The following research results have been achieved:(1)According to the fractal theory,the No.2,No.10 and No.12 mines are divided into 500 m * 500 m blocks,the fractal dimension values of the faults of No.2 mine,No.10 mine and No.12 mine are obtained respectively.According to the fractal dimensions,the fault complexity can be divided into four parts.The results show that the fault complexity of No.2,No.10 and No.12 mines is simple to simpler.(2)The water pressure of confined aquifer,the water richness of the aquifer,thickness of coal seam,thickness of aquiclude and complexity of fault are selected as evaluation factors.Through the gray correlation analysis method and the three-scale analytic hierarchy process,the subjective and objective weights of the evaluation factors are respectively obtained,and the combined weighting method is used to compound the subjective and objective weights,that is,the constant weight.According to the variable weight theory,the constant weight and state variable weight vectors are combined to calculate the variable weight of No.2 mine,No.10 mine and No.12 mine respectively.(3)Based on the hydrogeological data of No.2 mine,No.10 mine and No.12 mine in Pingdingshan coalfield,five evaluation models are constructed,including matter-element extension model,fuzzy variable set,catastrophe theory,fuzzy comprehensive evaluation and water inrush coefficient method.The risk of water inrush from the floor of No.2 mine,No.10 mine and No.12 mine is evaluated respectively.The geometric distance between the evaluation results of each model and the mean value of the evaluation results of the five models is calculated.The distance between the fuzzy variable set and the catastrophe theory is the smallest,and the priority of the four models is: fuzzy variable set< water inrush coefficient method<matter element extension model< fuzzy comprehensive evaluation< catastrophe theory.(4)Combined with variable weight theory and fuzzy variable set,the risk of water inrush from coal seam floor of No.2 mine,No.10 mine and No.12 mine is evaluated respectively.Based on the level characteristic value,the risk of water inrush from coal seam floor is divided into four levels.The level characteristic value is between 0-1.5,which is basically a safe area;the level characteristic value is between1.5-2.5,which belongs to the low threat area,the level characteristic value is between2.5-3.5,which belongs to the high threat area,and the level characteristic value is between 3.5-4.5,which is a dangerous area.