Abstract: Aiming at fully-mechanized top-coal caving face with great mining height in extra-thick coal seam, the coal mass affected by abutment pressure is divided into three zones, the fracture zone, the plastic zone and the elastic zone. A mechanical model of rib spalling affected by abutment pressure is established. With Mohr-Coulomb yield criterion and non-associated elastoplastic analysis, analytical expressions of coal wall horizontal displacement and the fracture zone and the plastic zone radii, are obtained by considering the hydraulic support protecting unit strength. At the same time, the main factors of rib spalling are analyzed. The model is demonstrated by comparing the theoretical results with the results of field measurement, the error is only 15.6%. The results show that with the increasing of abutment pressure concentration factor and cutting height and the decreasing of hydraulic support protecting unit strength, the horizontal displacement of coal wall increases and the extent of rib spalling is worse. Some measures, such as improving support resistance, reducing the pressure of coal wall, controlling the cutting height and increasing the protecting unit strength, are adopted to decrease the rib spalling.

Key words: extra-thick coal seam, fully-mechanized top-coal caving with great mining height, rib spalling, abutment pressure