Experimental research on the electrical parameters of coal mass under load

In order to investigate the relationship between the instability and failure of coal mass and the process of development, initiation and occurrence of coal/rock dynamic catastrophe. Study on the change laws of electrical parameters of coal mass under load by using the method of combining mechanics and electricity and obtain the electrical parameter-strain curves in the process of uniaxial compression and the corresponding stress-strain curves. The experimental results show that in the process of instability and failure of coal mass, there is a clear anti-symmetry between the change law of stress-strain curve and that of resistivity-strain curve with its minimum value corresponding to the cracking stress of coals, and the resistivity of the low rank coal and the high rank gently decrease without appearance of abrupt change no matter what the structural type of coal samples belong to, however the resistivity of the medium rank coals abruptly decrease when external load reaches approximately 75% and 85% of compressive strength value for the tectonic coal and the undeformed coal, respectively. In addition, it is also observed that there is a maximum value corresponding to the cracking stress of coals for dielectric constant in all the dielectric constant strain curves and the dielectric constant strain curves of the tectonic coal are better fitting to the corresponding stress strain curves, which is independent on the metamorphic grade of coal.