Abstract: Background, aim, and scope In recent years, mining technology and technology level has been rapid development, the number of long working face and deep mining face is increasing, and the problem of water damage of floor in our country is increasing. This problem has been paid more and more attention by many experts and scholars in the industry. The Wu Qiang academician applied the vulnerability index method and GIS system to study the causes and prediction of the floor water damage, and put forward the "three graph double prediction" method, which has received great attention in the industry and site application effect has also been unanimously praised. Professor Jiang Zhenquan and Professor Wang Lianguo have also made some achievements in the research on the developmental characteristics and distribution of the failure zone in the floor, and put forward the method of judging the water inrush from the floor. Professor Shi Longqing and his team have made an in-depth study on the influencing factors of the depth of the failure of the floor, and established the prediction model of the depth of the failure zone of the floor according to the influence degree of each factor. This paper mainly studies the influence of coal seam dip angle on the depth of failure zone in floor. Materials and methodsThe stress distribution characteristics of the posterior floor of the inclined working face are analyzed by using the fracture mechanics, and the failure zone calculation model of the lower edge and the upper edge of the inclined working face is established based on the fracture mechanics model. Results From the above calculation model of the failure zone, the damage zone of the upper and lower edges is the same when the dip angle of the coal seam is 0 °, and the depth of the failure zone of the lower edge is larger than that of the upper edge when the dip angle of the coal seam is not 0 °. The depth of the failure zone at the upper edge of the working face decreases with the increase of the inclination angle of the working face, and the depth of the failure zone of the lower edge increases with the increase of the inclination angle. DiscussionFrom the case of water bursting in China's coal mine and the depth of the inclination working face can be seen: The location of the water burst occurs mostly at the lower edge of the inclination working face, and the depth of the failure zone of the bottom plate is increasing with the increase of the inclination angle of the coal seam. ConclusionsThe results of theoretical analysis and statistical data can be concluded that the dip angle of the coal seam has a significant effect on the depth of the failure zone of the floor. With the increase of the dip angle of the coal seam, the depth of the lower edge of the inclined working face becomes larger and the depth of the upper edge is smaller. Recommendations and perspectivesThe established failure zone depth calculation model was subjected to quality inspection. The model is used to calculate the depth of the failure zone under actual conditions, and compared with the observed failure zone depth. The average error between the calculated result and the measured result is 1.20m, which indicates that the model has high accuracy and meets the requirements in engineering application.
Keywords: failing zone of floor; depth of failing zone; dip angle of coal seam; inclined length of working face; compressive strength