Surrounding rock stress evolution law of sectional mining in nearly vertical ultra thick seam

Based on a high mine strata pressure behavior problem occurred in the horizontal sectional mining process of the near vertical ultra thick seam,the site mea surement,mechanics analysis and numerical simulation calculation method were applied to the study on the surrounding rock movement features and the mine strata behav ior stress evolution law. The study showed that the surrounding rock movement of the horizontal sectional mining in the near vertical ultra thick seam was highly influenced by the mining and driving interferences and the main concentrations were in the mining level and the level below scope. The horizontal stress was the main factor affected t 0 the surrounding rock movement and the mine strata pressure behavior. The stress concentration phenomenon was occurred in the mining level and the level below scop e. The horizontal stress was in a similar " saddle" type distribution,the main influence scope was within 0 ~ 50 m below the mining level and the peak location was at about 30 m below the mining level. When the stress concentration coefficient was 1. 55,the failure type of the surrounding rock in the overburden goaf was a near vertical semi-ci rcular arch. The study results in a certain degree explained the strong floor heave and mine strata pressure behavior phenomenon occurred in the mining level and the bell ow level.