Experimental research on electrical resistivity variation of coal under different loading modes

In order to investigate the variation regularity of coal mass electrical resistivity in a complex stress environment, a real-time testing system of resistivity variation regularities of coal under loading was established in this study. Through this testing system, resistivity variations of coal mass under uniaxial compression, cyclic loading, multi-stage loading, stress relaxation, and creep loading were tested, respectively. Also, field emission scanning electron microscopy (FE-SEM) was carried out on coal mass. Ultimately, the variation characteristics and micro-mechanism of coal mass resistivity under different loading modes were discussed in depth. The research results indicated that the electrical resistivity of the coal mass varies with stress under different loading modes. The results also suggested that there are great correlations between axial stress, axial strain, and resistivity. Furthermore, it was found that the variation regularity of coal mass electrical resistivity changes with the change of pore structure during mechanical loading. Considering the variations of the axial stress and porosity during uniaxial compression, it was also demonstrated that the electrical resistivity of the coal mass is dominated by its pore structure and characteristics.