Experimental study on dynamic impact of hydrothermal treated coal in different coal ranks

Abstract

The new supercritical hydrothermal fracturing technology possesses promising applications in the field of coal and coalbed methane extraction. The research designed hydrothermal processing and true triaxial Hopkinson bar impact fracturing experiments on coals of different coal rank, measured the damage using acoustic waves and scanning electron microscopy. The results of the study showed that: 1. Hydrothermal treatment caused initial damage to coals in different coal ranks, resulted in the reduction of coal acoustic wave speed and dynamic strength. 2. As the coal rank advanced, the metamorphic degree of coal increased and its dynamic strength increased, and the dynamic strength of anthracite reached 149.79 MPa. 3. A pore expansion model of hydrothermally treated coal was established, which indicated that the porosity of hydrothermally fractured coal increased as a whole but the distribution of pore size was more concentrated in the process of hydrothermal fracturing in conjunction with adsorption resolution curves. 4. A dynamic damage constitutive model of coal after hydrothermal treatment under true triaxial circumferential pressure was proposed, which had great significance for evaluating the dynamic disaster safety after hydrothermal fracturing in coal mines.