Load and instability characteristics of support in large mining height fully-mechanized face in steeply dipping seam

The stability control of support is a technical problem to be solved urgently in steeply dipping thick seam mining. Based on the geological conditions and characteristics of strata behaviors of No. 25221 working face in 2130 Coal Mine,China,the overburden migration law and load characteristics of support is analyzed with field monitoring, and the theoretical analysis is used to research the influence of mining height and roof movement on the load and insta- bility of supports. Results show that the movement amplitude and intensity of the roof and working resistance of support are higher than those of normal mining height face in steeply dipping seam,which is due to mining height increase. When the roof and floor of working face is stable,the critical working resistance of support is less than two times the weight of support. However,with the influence of roof movement,the support will also move with the movement of the roof,which would not disappear with the increase of the working resistance of support. The movement amplitude and instability probability of the support are increased with the decrease of the working resistance of support and the in- crease of the friction between the roof and the support,the partial loading degree of roof load and mining height. In ad- dition,the probability of rotation instability in large mining height fully-mechanized face in steeply dipping seam is greater than that of falling instability,and this phenomenon will be obvious with the increase of mining height.