Influence of coal mining on the deformation-failure and permeability of seam floor

Except the geological factors, the deformation and failure of seam floor are also controlled by mining factors. The influence of coal mining on stress-strain and permeability of seam floor in working face and its failure regularities were studied through theoretical analysis and the experiment. The research result shows that the permeability of the rock with different lithology is a function of strain in the process of complete stress-strain. In the micro-fracture closure and elastic deformation stage, the primary pores and cracks of rocks are easily compacted, it is obviously that rock permeability decreases with the increase of stress, when the stress intensity increases to the limit, the rock sample is destroyed and cracks through the sample are formed,, the rock permeability rapidly increases to the maximum. There are some differences between rocks with different lithology. With advancement of working face, the seam floor rocks are divided into four areas horizontally, they are initial stress area, advanced stress compression area, direct damaged area of mining stress and stress recovery area of floor rock mass. Permeability of seam floor rock shows regular variation with the deformation and failure of seam floor rock during coal mining.