Full-Field Deformation and Crack Development Evolution of Red Sandstone under Impact and Chemical Erosion

Abstract

Coal mine reuse involves complex environments such as chemical erosion and dynamic perturbation. Therefore, the effect of chemical erosion on the dynamic behavior of the red sandstone was studied by split Hopkinson pressure bar (SHPB) tests under the strain rates of 70~125 s−1. The full-field deformation of the sample was then recorded through high-speed 3D digital image correlation (3D-DIC) technique. The dynamic deformation characteristics, especially the lateral strain, were extracted by averaging the lateral strain field by pixels. Also, the fracture behavior was investigated based on the evolution of strain localization in the strain field. The results indicated that the deformation field evolution of the sample is controlled by the chemical erosion effect and the loading strain rate. The chemical erosion lowers the stress threshold for strain localization and accelerates its expansion rate, which is closely related to the dynamic strength degradation of the sample. In contrast, the loading strain rate increases the dynamic strength but advances the occurrence of strain localization and shortens the time to the peak stress. The normalized stress thresholds for the initiation and development of cracks inside the sample under dynamic loading are reduced by chemical erosion, with the two thresholds dropping to 10%~30% and 20%~70% of the peak stress, respectively. The minimum thresholds for the initiation and development of cracks inside the red sandstone under dynamic loading are 11% and 24% of the peak stress, respectively.