Review of theoretical and experimental studies on mechanical rock fragmentation using microwave-assisted approach

The microwave-assisted mechanical rock breaking system is a rock fragmentation method which uses the combination of microwave heating technology and the mechanical excavating technology. Different minerals have different degrees of absorption to microwave energy, so intergranular and transgranular fractures occur within the specimen after microwave radiation treatment, and the specimen is weakened and micro cracks are generated due to the internal stress caused by thermal expansion of different minerals within the rocks. This causes the rock strength to be reduced. Microwave power and exposure time are the important parameters to influence the mechanical properties of rocks. The point load strength, tensile strength and compressive strength decrease significantly with a certain power level of microwave radiation. The higher the microwave power and the longer the exposure time, the more the strength reduction. The numerical results are compared with the experimental ones and show that the strength reduction is much quicker by increasing the power level of microwave in shorter time of exposure. The life and penetration rate of cutters of the rock mechanical equipment can be increased by the strength reduction of rocks, which can contribute to resolving the disc cutter wear problem. Microwave-assisted mechanical rock breaking has significant influence on drilling, TBM tunnelling and realizing the continuous mining of metal mine.