Abstract: The roof abscission of the coal seam and rock strata is the omen to the final loosing stability of the roadway with extra-thick coal seam (RETCS) during the excavation and mining activities. It is a basic research on the key influencing factors of the roof abscission as this study can effectively control the value and regeneration of the roof abscission and decrease the roof abscission occurrence ratio, which can prevent the roof caving accidents. Combined with field observation, numerical simulation, orthogonal test and theoretical analysis methods, the influencing factors of the roof abscission of the RETCS are classified and the simulation methods of the roof abscission and key influencing factors of the roof abscission of the RETCS are analyzed in detail. Finally, the main results are as follows：1) The influencing factors of the roof abscission are classified into 3 broad categories including supporting parameters, coal seam and parting properties and roadway structural arrangement and 15 concrete types. 2) The simulation and calculation methods between finite element and discrete element are compared and the latter software with block inlay type are determined and chosen. 3) Based on UDEC and orthogonal test, a total of 50 numerical models according to the 15 influencing factors of the roof abscission are built and simulated and 3 categories of influencing sequence chart and 6 key influencing factors are obtained.

Key words: extra-thick coal seam, roof abscission, influencing factors, orthogonal test