Influence of Overlying Strata Movement on the Stability of Coal in Fully Mechanized Top-Coal Caving Mining

Overlying strata movement has an important effect on the stability of coal along goaf. In order to study the impact of overlying strata movement on the stability of coal during fully mechanized top-coal caving mining, a simulation experiment was conducted on the Liuxiang Coal Mine using digital image correlation (DIC) and stress electric measurement methods. The characteristics of overlying strata movement, stress concentration and deformation evolution of coal, and interlayer sliding between coal and rock are analyzed. The following conclusions could be drawn. The movement of overlying strata can be classified into two stages: the first stage is characterized by vertical displacement, while the second stage is characterized by horizontal displacement. In the first stage, the vertical movement of overlying strata causes the vertical stress concentration of the coal. In the second stage, the horizontal movement causes frictional sliding between coal and rock, which produces a shearing effect on the coal. Under these two effects, the coal along goaf gradually reaches its strength limit, and local deformation occurs, and the micro-cracks are further concentrated and fused in this area. When macro-cracks are formed, occur and expand unstable, the elastic energy is released suddenly, which will lead to dynamic disasters such as rock bursts.