Quantitative Analysis of Infrared Thermal Images in Rock Fractures Based on Multi-Fractal Theory

Rock disasters caused by rock fractures seriously threaten the safe and sustainable mining of deep coal resources. The infrared thermal imaging of rock fractures has a non-uniform distribution. This is important information for the monitoring and early warning of rock mass instability. In this paper, the multi-fractal theory was introduced to analyze the infrared thermal image obtained from the uniaxial loading of sandstone, which is expected to provide quantitative indicators for the infrared monitoring of rock failure. The results show that the multi-fractal parameters Delta alpha. (non-uniformity of temperature) and Delta f (frequency diversity of minimum and maximum temperature) can be used to describe the distribution of the thermal field; they are sensitive to the rock macro fracture. Both Delta alpha. and Delta f are constant during the initial loading stage. When the samples yield and there is a failure in the later stage of loading, the Delta alpha. and Delta f change abruptly. The sudden change in Delta alpha. and Delta f can be regarded as the precursor to rock failure. The research results preliminarily show the feasibility and potential of multi-fractal analysis in rock mass disaster monitoring and early warning.