MMIJ Annual Meeting

The peak value of mining pressure on hydraulic support is supposed to increase with the mining height in the longwall top-coal caving mining. The supporting pressure of hydraulic support is therefore selected based on the mining height. However, it is also known that the pressure may not significantly increase as expected. This study mainly aims to clarify the effects of the loose top-coal on the reduction of the mining pressure of the hydraulic support for the geological conditions of Jiaozuo Coal Mine in Henan Province, China. A series of dynamic loading tests for loose top-coal, which was simulated by particles having different types and sizes, with different thicknesses, was carried out. It was found that the buffering effect became more prominent for softer or larger particles, or with the thickness within a certain value. The interaction model between the support and loose top-coal was built and the constitutive equations between them were derived. In the analysis using the constitutive equations, it was confirmed that the top-coal became more stable with the stiffness of the support. It was found from the numerical analysis using ANSYS software that the stratification of stress occurred during the propagation of loading in the top-coal and that the buffering effect became better with the thickness within a certain value.