Process and mechanism of blasting damage and fracture of calcium conglomerate in Hushan ranium mine

To study the damage law of calcareous conglomerate under blasting, firstly, the damage fracture process and mechanism of calcareous conglomerate under blasting load were revealed based on the theory of damage fracture mechanics. A meso-scale model of conglomerate, including filler, conglomerate and interfacial transition zone (ITZ), was established by using LS-DYNA and Fortran programming, and the propagation law of explosive stress wave and its damage characteristics were analyzed. The damage fracture process of calcareous conglomerate under blasting can be divided into four stages, namely: compression damage in both gravel and fill; tensile damage in gravel and compression damage in fill; tensile damage in both gravel and fill; and tensile damage at the intersection of gravel and fill. Numerical results show that under blasting loads, the gravel has higher equivalent stresses, the fill has the lowest, stress concentration is evident at the ITZ, and the stress gap between the gravel and the fill decreases as the distance increases. The conglomerate sustains relatively minor damage, with a notable phenomenon of damage occurring around it. However, the filler experiences significant damage. The expansion of blasting crack in calcareous conglomerate forms mainly along the direction of stress wave propagation. Cracks tend to develop along the filler with lower physical and mechanical properties, as well as along the junction surfaces. The damage to the gravel is comparatively less severe. Blasting blockiness is mainly manifested as the filler wrapping gravel, and the distribution of blasting blockiness is affected by the bonding force at the intersection surface and the distribution of gravel.