Risk Assessment Of Roof Sandstone Water Irruption Under Complicated Mining Condition

Sandstone fractured aquifer is common in coal-bearing strata and the direct water inrush source of mining. With the increase of mining depth and the increasingly complicated mining conditions, frequency and water inflow of roof sandstone water hazard increasing. It has already became the main type of mine water disaster. Roof sandstone water hazard frequent occurrence and serious impact on mine production safety in yangzhuang coal mine which is one of seven extremely complicated Mines in Anhui.Coal-bearing strata sanstone aquifer’s water abundance is very uneven, basically with poor water abundance and mainly static reserve. But there are more fracture in core of fold structure or the connector location of core and the limb of fold structure, thus the water abundance is good. Roof sandstone water inrush relative to not only sandstone water abundance, but also relative to rock structure and development rules of water flowing fractured zone. There were many water inrush accidents happened during5th coal mining, and were7water inrush accidents were in WIII5110working face. The maximum water inrush value reached100m3/h. Take5th coal roof sandstone water hazard as the research background. Through surface drilling, geophysical prospecting of working face, hydrogeological tests and rock mechanics test. Comparative analysis hydrogeology conditions, engineering geological conditions, characteristics of structural geology and mining conditions between water-bust face and none water-bust face. Comprehensive consideration water inrush factors of5th coal roof sandstone, such as roof sandstone water inrush factors, mining practice of5th coal and characteristics of roof sandstone water inrush. Determined water bundance of sandstone, characteristics of overlyling rock structure, characteristics of strata sehaviors, roof abscission layer water and structural geology conditions are the main factors of roof sandstone water inrush.Established analytic hierarchy structure, construct and compute the judgment matrix based on relation between factors, expert estimation system and Matlab tool box. Determined weighting of factors and Established assessing scale set. Taken characteristics of overlying rock structure, hydrogeology conditions and characteristics of strata behaviors as subordinated target layer. Taken thickness of roof sanstone, height of caving zone and fractured zone, distribution of magmatic rock, water abundance of roof sandstone, development of sandstone fracture, haracteristics of water control structure, water abundance abnormal area of roof sandstone, roof mine pressure, pressure step and range of mine pressure as rule hierarchy. Computed and analysed evaluation result of water-bust face and none water-bust face, realized training and optimization of model. Evaluated the NⅡ529working face based on dangerous degree of roof sandstone water inrush model. Evaluation result is0.4117, shows the overall safety of NⅡ529working face is good, possibility of roof sandstone water inrush is small.