Regularity and mechanism of coal resistivity response with different conductive characteristics in complete stress–strain process

The stress, strain as well as resistivity of coal during uniaxial compression process were tested based on self-built real-time testing system of loaded coal resistivity. Furthermore, the coal resistivity regularity and mechanism were analyzed at different stages of complete stress–strain process, which includes the two kinds of coal body with typical conductive characteristics. The results indicate that coal resistivity with different conductive characteristics has different change rules in complete stress–strain process. It is mainly represented at the densification and flexibility phases before dilatation occurs. The variation of resistivity can be divided into two kinds, named down and up. Dilatation of coal samples occurred between 66%σmax and 87%σmax. Because of dilatation, coal resistivity involves sudden change. The overall representation is shifting from reducing into improving or from slow improving into accelerated improving. Thus, coal resistivity always shows an increasing tendency at the plastic stage. After peak stress, coal body enters into failure stage. The expanding and communicating of macro fracture causes further improvement of coal resistivity. The maximum value of resistivity rangeability named λ reached 3.49. Through making real-time monitoring on coal resistivity, variation rules of resistivity can be deemed as precursory information so as to reflect the dilatation and sudden change before coal body reaches buckling failure, which can provide a new technological means for forecasting the dynamic disaster of coal petrography.