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.