Deformation Mechanisms and Macromolecular Structure Response of Anthracite under Different Stress

It has been controversial whether tectonic stress affects the chemical structure of coals. To further understand if and how tectonic stress affects the chemical structure of coals, an investigation into the macromolecular-level deformation mechanism is quite necessary. Therefore, we performed deformation experiments on anthracite with axial load both parallel and perpendicular to the bedding plane. Macromolecular structure variations during deformation were revealed by a combination of Raman spectroscopy and high-resolution transmission electron microscopy. Results show that (1) coal deformation behaviors (brittle deformation or ductile deformation) are influenced by stress direction, in addition to the temperature and strain rate, and (2) ductile deformation is related to the growth of defects, which is more favorable under stress parallel to the bedding plane, at higher temperature and lower strain rate, while brittle deformation is presumably due to the direct bond breakage beyond the elastic limit. On...