Study on surrounding rock stress distribution characteristics andsidewall failure mechanism of seam gateway

In order to study the stress distribution features of the excavated surrounding rock in the mine seam gateway and based on the analysis on the failure mechanism and the influence factors of the seam gateway sidewalls, a numerical experiment study means was applied to analyze the vertical and horizontal stress distribution law of the excavated surrounding rock in the mine seam gateway and the height influences of the gateway sidewalls and to analyze the full stress variation process of the surrounding rock. A failure mechanism theoretical model of the seam gateway sidewalls under the excavation unloading stress path was established. The coal mass of the seam gateway sidewalls affected by the unloaded stress role was divided to a creaking zone, plastic zone and elastic zone. An analytic expression of the creaking zone in the coal mass of the gateway sidewalls and the stress in the plastic zone, width of the creaking zone, scope of the non elastic zone and the horizontal displacement value was derived. The study results showed that the excavation would cause the vertical stress increased on the coal mass within a certain scope of the gateway sidewalls, the horizontal stress would be continuously decreased and the difference between the two stresses would be continuously increased. The surrounding rock would be pressed from the three dimensions to the two dimensions, the stress balance status would be broken and the deformation failure would be occurred. With the application of the high pre-stressed powerful bolt support, a pressure stress field with a certain scope would be occurred in the surrounding rock of the seam gateway and the three dimension pressurized status of the coal mass in the gateway sidewalls would be recovered steadily.The engineering cases verified that the support intensity increased within a certain scope could reduce the deformation failure degree of the gateway sidewalls, but the influences would be steadily reduced.