Evolution Analysis Of Floor Failure Characteristics Driven By Coal Mining In Yangdong Mine

The Fengfeng mining area is one of the main coals producing areas in China.There have been experienced many floor water inrush accidents,which have a very adverse impact on the safety production of coal mines.With the gradual exhaustion of shallow resources,the mines that have been put into production have been or will be transferred to deep mining.In the face of complex deep environment,once the floor water inrush accident occurs,it is often accompanied by the characteristics of large energy,unclear mechanism and difficult to get effective control,resulting in greater economic losses,etc.In all kinds of floor water inrush accidents,the research shows that the floor water inrush is mainly due to the floor damage,which reduces the thickness of the effective aquiclude and increases the invasion ability of the floor aquifer.Consequently,studying the evolution law of floor failure characteristics is meaningful to us in the process of coal mining.Taking Yangdong mine,one of the main coal producing areas in Fengfeng mining area,this paper takes the actual situation of its 8469 working face as the research object.Based on the theoretical research,combined with the field water injection test and numerical simulation,the failure characteristics of the floor in the process of mining are studied.At the same time,from the two angles of coal seam buried depth and coal seam dip angle,respectively,to explore its impact on the floor damage.The results show that the stress on the surrounding coal and rock mass is divided into different stress zones due to mining disturbance,and the distribution is"saddle-shaped".Under the action of inclined shear stress component,the floor mining failure zone will slide downward,and the failure shape is"spoon-shaped".In the numerical simulation,it can be seen that the failure range of the floor changes linearly with the increase of the excavation distance.When the excavation distance is certain,the plastic failure range only expands along the advancing direction,and the failure depth reaches the maximum.The smaller the principal stress ratio(?₃/?₁)is,the easier the rock is to yield,and the more cracks are produced,according to the characterization parameters of principal stress.In the field test,with the change of water injection quantity in different positions,it is concluded that the fracture development degree is proportional to the water injection quantity,and the disturbance influence degree gradually decreases with the increase of depth.The results of the above methods for the maximum failure depth of the floor are relatively close,that is 25 m?29.2 m.As for analysis of different influencing factors,it is found that the variation of floor stress and failure range are positively correlated with the burial depth and dip angle of coal seam.Among them,when the burial depth is the same,the larger the dip angle is,the easier the floor rock damage is to shift to the lower part of the working face,and the more obvious the"spoon"shape is.The maximum failure depth of the floor is linearly increasing with the change of the dip angle when the dip angle of the coal seam is less than 30°;As the dip angle is greater than 30°,the maximum failure depth of the floor gradually decreases,indicating that the rock seam of the floor is most affected by the stress disturbance in the range of 30°?40°,causing more rock strata to be destroyed.