Brittle–Ductile Transition of Mudstone in Coal Measure Rock Strata under High Temperature

In this paper, mudstone in coal measure rock strata was investigated to understand the brittle–ductile transition characteristics of mudstone under high temperature. An electrohydraulic servo system, high-temperature furnace, and scanning electron microscope were used during high-temperature mechanical tests and scanning electron microscopy experiments which focused on studying the effects of temperature on the yield strain, peak strain, ductility coefficient, and stress–strain relationship of mudstone. The results showed that, for the most part, the yield strain of mudstone first increased and then decreased as temperature increased. At temperatures below 700°C, the mudstone was primarily brittle, and at about 800°C, the brittle–ductile transition of the mudstone occurred under the effects of high temperature. At this transition temperature, granular cracks, intergranular cracks, and transgranular cracks in the mudstone crystal formed a large crack network structure, and the mudstone samples showed ductile failure characteristics.