Study of dynamic mechanical characterization of coal with different metamorphism degrees under hydraulic fracturing

The application of hydraulic fracturing technology to coal bed methane mining could not only realise extremely high economic benefits, but also reduce the sources of mine hazards. As new technologies develop, more and more fracturing fluids were starting to appear on the market, and the dynamic mechanical properties of coal rock after large-scale fracturing are of great significance for the prevention and control of dynamic hazards in deep mines. The primary findings of the research were: 1. Acid treatment and fracturing fluid treatment caused initial cracks in the coal samples, and the damage caused by the fractionating fluid was more serious;2. Different degree of damage of coal solution treatment for different coal rank, and the damage of coal with high degree of metamorphism was more serious, due to its higher mineral content; 3. Dynamic impact damage was divided into three stages, and the dynamic damage model was constructed to reveal the dynamic damage mechanism of the coal in true three-dimensional; 4. The solution processing model of coal was constructed by energy spectrum analysis to explain the damage principle, and the framework of coal pore and crevice evolution was constructed from the microscopic point of view.