Mechanical analysis of support stability in longwall mining of steeply dipping seam

The key of safe and high efficiency mining in the longwall mining of steeply dipping seam is the effective control of surrounding rock,and the difficult point in surrounding rock control lies in the stability control of “support- surrounding rock” system. Based on the comprehensive definition and research on the interaction relationship of “roof- support-floor” system in the working face,a mechanical model of support in inclined direction is established to model the behavior response of support under roof load. Besides the influence of mining height,the floor physical and mechanical properties and interaction between supports on the stability of supports are discussed. Results show that under the load of self weight and overlying strata,the roof of the working face is in a state of discontinuous motion in steeply dipping seam mining,and the motion direction is along the curve in the direction of gravity. As a result,the support will also move with the movement of the roof of working face,and the motion amplitude of support is in a discontinuous progressive accumulation process. The stability of the support increases with the increase of normal roof load,the de- crease of the tangential roof load,the decrease of the partial roof loading degree,the increase of floor hardness,the de- crease of the mining height and the increase of jack stiffness of side protecting plate of support. The normal load of roof,foundation coefficient of floor,the mining height and jack stiffness of side protecting plate of support can only in- crease or decrease the movement amplitude of the support to a certain extent. However,the tangential load of roof and the roof load location can not only affect the movement amplitude of the support,but also change the direction of its movement. Compared with other factors,it has a significant impact on the stability of the support. Therefore,there is an effective way to control the stability of the support by strictly controlling the stability of the roof in the middle and up- per parts of the inclined working face and timely adjusting the position of the support,so as to reduce the tangential roof load and its eccentric degree.