Experimental study on improving mechanical mining efficiency of deep banded iron ore by microwave presplitting

Microwave-assisted mechanical mining is a new mining method with great potential. A self-developed true triaxial system for microwave-induced fracturing and cutting of hard rocks was used to study the microwave cracking process, cracking mechanism, and its effects on subsequent cutting, grinding and mineral dissociation by taking Sishanling banded iron ore as the research object. The results show that compared with microwave irradiation alone, the failure mode and mechanism of ore samples were more complex under the combined action of true triaxial stress and microwaves. Large cracks that were parallel to the bedding plane appeared in the sample under microwave irradiation without triaxial stress. When true triaxial stress and microwave irradiation were used simultaneously, the surface of the sample was subject to spalling or spalling and cracking. Additionally, the correlation (parallel or vertical) between the direction of σ1 and the direction of the bedding plane affected the fracture characteristics. Microwave irradiation could promote subsequent mechanical mining, grinding, and beneficiation of samples. Compared with no microwave treatment, under the action of stress and microwaves, the total amount of rock breakage of samples was increased by 55.1%, the powder content of the product after grinding of cut particles was increased by 21.9%, and the degrees of dissociation of cutting products (<0.1 mm and <0.2 mm) were increased by 11.6 and 12.7%, respectively. The influence of the strip width of magnetite on the microwave cracking effect of ore was estimated. At a given magnetite content, the microwave absorption was worse for wider strips, and the reflection performance was similar for strips of various widths.