Study of Countermeasures and Abnormal Pressure Principle During Non Pressure Period Under Room and Pillar Goaf

To abnormal pressures problem during fully mechanized working face mining under room and pillar goaf of one coal mine in the western mining area，based on abnormal pressures characters and practical test and theory analysis， then abutment pressure distribution law of residual coal pillar upper and coal pillar stability were analyzed，it’s occurrence mechanism and countermeasures were studied. The results showed that residual coal pillar would failure as abutment pressure was larger，when the first breakdown appearedin the roof，residual coal pillar maintaining stability during the first breakdown，but the superposition abutment pressure that formed upper of the working face and overburden within two spans backward of working face was larger，then residual coal pillar would failure，dynamic loading would appeared in interlayers of rock stratum，which formed by coal pillar roof after coal pillar failure，residual coal pillar chain failure appeared in non pressures period，the number key stratum was only 0～1 between inter layers，then abnormal pressure would appeared, pressurizing of hydraulic support disaster would appeared as residual coal pillar chain failure appeared during pressuring period，the following countermeasures as coal pillar blasting，goaf filling and decrease advancing speed were put forward. Key words：room and pillar goaf；abnormal pressure；residual coal pillar；dynamic loading；countermeasures