Resistivity Response Characteristics of Coal and Coal-like Materials under Uniaxial Compression

Resistivity is the core electrical parameter of coal-field electrical prospecting technology to identify geological anomaly areas. Studying the change characteristics of the resistivity of coal under loading is helpful to further improve the accuracy of electric prospecting in delineating the abrupt change area of coal structure and to enhance the ability to reduce and avoid disasters in coal mine production processes. In this study, the resistivity of raw coal and coal-like specimens was monitored under uniaxial compression. The influence mechanism of the coupling structure and moisture on the resistivity of raw coal and coal-like specimens was analyzed. Additionally, the change law of the electrical characteristics during the instability process and the corresponding relationship between the resistivity change and the mechanical behavior of specimens were characterized. The results show that the uniaxial compressive strength and elastic modulus of raw coal specimens are close to the similar-material specimens but much larger than the coal briquette specimens, and the effect of water on similar-material specimens is greater than the coal briquette specimens. The curve of resistivity change over time can be divided into four stages according to the change process of the stress–strain curve. The resistivity of the specimens in stages I and II exhibited a decreasing trend, except for the specimens of similar materials under natural conditions. The trends of the different types of specimens in Stage III were different, and the specimens in Stage IV showed an increasing trend. The order of the resistivity change rate at the stress peak compared to the initial point was as follows: natural similar-material specimen > water-soaked briquette > raw coal > natural briquette > water-soaked similar-material specimen. The experimental results provided theoretical support for further understanding the differences between coal-like materials and raw coal.