Acoustic emission fractal-permeability model and experimental study of coal specimens under hydraulic-loading coupling

The fracture (pore) development of coal specimen under axial stress loading and hydraulic permeability affects directly the mechanical indexes and the permeability characteristics. In this paper, using theoretical analysis and mechanical test methods, the relationships between permeability and fractal dimension, ringing count response under coal specimen fracture (pore) were analyzed, and the acoustic emission fractal-permeability model of coal specimens under hydraulic-loading coupling were established. The permeability experiments of coal specimens with hydraulic-loading coupling in different confining pressures (2−5 MPa，Δpw/p'c=0.75) were carried out, and the mechanical behavior, permeability characteristics and acoustic emission rules of coal specimens in different confining pressures (water pressure) were analyzed, and the relationship between the failure morphology of coal samples under different confining pressures and the acoustic emission positioning was discussed. The strength enhancement characteri