Study On The Pressure Behavior Of "Two Soft And One Hard" Top Coal Caving In Unstable Coal Seam Face And Control Technology

For the strata behavior problems of the big gateway pressure and severe rib spall occurring in "two-soft and one-hard" unstable coal seam in the YUNMei second mine, the paper analyzed and researched the problems by adopting synthetically the methods of laboratory testing of rock physical parameters, similar simulation experiment, field measurement, theoretical analysis and numerical simulation under the engineering background of NO.22202 fully mechanized top-coal caving face.Firstly, rock mechanical parameters of the roof and floor rock of the face were obtained by laboratory testing. On the basis of the parameters, the mechanism and influencing factors of rib spall were analyzed, and abutment pressure distribution model in front of fully mechanized top-coal caving face were established, and then the width of the plastic zone in front of coal wall were calculated based on the actual mining conditions of NO.22202 fully mechanized top-coal caving face. Secondly, trans-falling and migration law of overlying stratum of the working face, stress distribution law and the height of upper three zones were obtained by laboratory similar simulation experiment. Thirdly, on the basis of the field measurement, the roof weighing and the rib spall situations of the working face were analyzed, and supports operation status were evaluated, and the roof and floor on the basis of laboratory testing of rock physical parameters and field measurement were classified. Finally, rib spall mechanism and factors of the fully mechanized caving face were researched deeply by applying numerical simulation FLAC3D software, and the relationship between the coal seam thicKNess, advance distance face, support resistance and plastic zone surrounding rock face, ahead of the stress distribution, rib spall were obtained.The results of the paper can be applied to guide the follow-up production of the working face to ensure the safety and high production and high efficiency production of the working face. At the same time, they provided the theoretical guidance for safe production of other fully mechanized top-coal caving face with similar geological conditions.