Coupling effect of mining-induced strain field and permeability coefficient field in surrounding rock of working face

The properties of mining-induced rock mass deformation and permeability are basic issues for water inrush prevention in working face. Based on the theoretical analysis and numerical simulation method, the deformation and permeability characteristics of the rock and its three-dimensional quantitative relationship are analyzed. The distribution of the stress field, the permeability field and the controlling factors of the surrounding rock in the coal mining face are studied. Results show that permeability coefficient of mining-induced fracture rock mass is closely related to its strain state and strain increment, and increases with the tensile strain perpendicular to the fractures. Strata in advanced abutment pressure area of working face and overall movement belt are compressed thus exhibit decreased permeability, while strata in caving zone and shallow layer forward the working face are in the state of stretching deformation and possess increasing permeability, which shows a larger range of increasing area about permeability coefficient vertically compared to horizontally. Vertical permeability variation dominates water burst in face when coal mining is underneath water bodies. Accelerating advance speed, decreasing dip length of working face and mining height can decrease the permeability coefficient increase degree of surrounding rock, and the variation range of permeability coefficient field is limited in neighboring mining area. Therefore, the influence on primary strata permeability induced by mining is minimized.