(1. Institute of Mining Technology，Taiyuan University of Technology，Taiyuan，Shanxi 030024，China； 2. Institute of Sciences，Taiyuan University of Technology，Taiyuan，Shanxi 030024，China)
Abstract：In accordance with upward mining for left-over coal owing to some historical reasons or complex geological conditions，the key technology in upward mining was proposed to control the strata，and its breakthrough point was to determine key position in rocks between strata. Because key strata structure among coal seams in upward mining has evolved to face-contacted block structure，appropriate parameter matrix was established based on block theory and its discrimination matrix is figured out in view of which the block in face-contacted block structure had high intensity and stiffness. The friction face among blocks was similar to a plane，and the structural face run through the block，and structural instability was caused by the shear slip of the block along contact faces. Vector analysis method was employed to determine the mobile block in key strata structure between coal seams in upward mining. Furthermore，the specific determination method for key position in rocks of strata controlling between coal seams for upward mining was explored by means of virtual tangential net slipping force，which provides a solid foundation for further exploration of strata structure between coal seams and technology system of upward mining .
