Brazil splitting characteristics of coal-backfilling composite structure with different interface angles: Insights from laboratory experiment and numerical simulation

The coal-backfilling composite structure jointly bears the overburden stress. The interface between the coal pillar and backfilling body can easily induce splitting failure of composite system. The failure pattern and load-acoustic emission (AE)-digital image correlation (DIC) response of coal-backfilling (CB) composite structures were investigated through Brazilian splitting tests. The mesoscopic force-fracture distribution, azimuth angle of contact force and displacement vector were then obtained from particle flow code (PFC) numerical simulations. The results show that three types of failure patterns are observed for different CB composite specimens during the Brazilian loading process; with an increase of interface angle, the failure shifts firstly from Type I to Type I-II pattern, then turns into Type III, and finally becomes Type II pattern; For the CB composite specimens with different interface angles, the load - AE - DIC response characteristics correspond to the failure patterns; tensile fracture is dominant when the fracture is distributed on coal or backfilling elements. The fracture may be tensile, shear, or combined tensile-shear fracture when the fracture occurs at the interface.

Automated summary

The failure patterns and load-AE-DIC response of coal-backfilling (CB) composite structures were investigated through Brazilian splitting tests. The numerical simulations showed that with an increase of interface angle, the failure shifted from Type I to Type I-II pattern, then turned into Type III, and finally became Type II pattern.