Numerical Simulation of Hard Roof's Safety Control

摘要

The key to safety control of the hard main roof is to limit the effect of impact as they break and fall. So, it is necessary to perform proper induced caving of hard roof in terms of time and operation to avoid its impact loading on supports of coal mine. However, in fully mechanized long-wall top-coal caving face, the periodical weight of roof is a main factor that crushes the top-coal, which is beneficial to the top-coal recovery. How to safely control the hard roof and to use the roof pressure is of crucial importance in long-wall hard top-coal caving in China. Base on field monitoring, theoretical analysis of strata movement, the numerical model of hard roofs cantilever structure was built, and the parameters of the model were also determined. The elastic-plastic finite element method was used to analyze the effect of hard coal cracking under the abutment pressure of hard roof, and the cracking coefficient of rock mass was defined according to the stress state of the element, therefore the top-coal cracking was described distinctly under the condition of different roof span and technology parameters. The rational cantilever length of hard roof was determined, and the rational working resistance of support was selected. As a result, the hard roof's safety control not only protects the top-coal caving working face, but also improves the caving ability of hard top coal to increases the recovery rate. The engineering practice of hard roof's safety control is presented in this paper.