Research on the process and mechanism of blasting damage and fracture of calcium conglomerate in Hushan ranium mine

Calcium conglomerate is the second largest type of uranium deposits in Namibia. Calcium conglomerate is extremely difficult to be broken due to its special structure, and even if the unit consumption of explosives reaches 1.0kg/m3, a large number of large and super-large blocks will be produced, which not only restricts the shoveling operation and seriously affects the production of the mines, but also greatly increases the costs and dangers of the secondary crushing, and it is the biggest problem encountered in the process of mining. In order to study the damage law of calcium conglomerate under the action of blasting, based on the theory of damage fracture mechanics and wave dynamics, the blasting damage fracture process and mechanism of calcium conglomerate were revealed, and the fine numerical model including filler, conglomerate and interface transition zone was established by combining LS-DYNA and Fortran programming, and the blasting stress wave propagation law and damage characteristics of calcium conglomerate were analyzed. The fracture process of the blasting damage of calcium-caking conglomerate can be divided into four stages, namely: compression damage occurs in both conglomerate and filler; tensile damage occurs in conglomerate and compression damage occurs in filler; tensile damage occurs in both conglomerate and filler; and tensile damage occurs in the interfacial interface of conglomerate and filler. Numerical results show that: gravel in the blasting load characterizes a higher equivalent force, the filler equivalent force is the smallest, the interface transition zone at the obvious stress concentration phenomenon, with the increase of the distance between the gravel and the filler to withstand the stress gap decreases. Conglomerate damage is small, there is damage “around the stone” phenomenon, filler damage is larger. Calcium-caking conglomerate blasting crack expansion form is mainly along the direction of propagation of the stress wave to preferentially select the lower mechanical properties of the filler and the development of the intersection surface, the damage to the gravel is weaker. Blasting blockiness is mainly manifested as the gravel wrapped by the filler, and the distribution of blasting blockiness is affected by the bonding force of the intersection surface and the distribution of the gravel.