Hard rock breaking is a great challenge for deep drilling and mining engineering, and the microwave-assisted rock breaking technique offers a promising solution. However, the lack of knowledge of the effects of microwave irradiation on hard rocks limits the further development of this technology. Laboratory tests have been conducted to investigate the variations of fracture properties of granite subjected to microwave heating. The semi-circular bend (SCB) specimens were prepared, and mode I fracture tests were conducted on the microwave treated granite specimens. The acoustic emission (AE) events was recorded and the strain field was calculated by the digital image correlation (DIC) technique. The test results demonstrated that the temperature of the sample surface increased linearly as the increasing heating time, and increasing microwave power contributes to enhancing the heating rate. According to the results of scanning electron microscope (SEM), intergranular cracks were the main form of cracks, and the transgranular cracks usually appeared in samples with high microwave power or longer heating time. The generation of micro-cracks can be attributed to the high temperature and the thermal shock. With the increasing heating time, the fracture toughness decreased exponentially, the AE active period prolonged, and the fractal dimension of the fracture surfaces (FSD) continuous increased. Compared to an untreated sample, the maximum principal strain and fracture process zone (FPZ) size of the microwave heated sample were larger at the same loading level, which indicated the enhancement of ductility. According to the experimental results, the relationships between FPZ size, fracture toughness and FSD were empirically regressed. Understanding the effects of microwave heating on the fracture properties is of significant to improve hard rock breaking efficiency.

坚硬的岩石破碎对深层钻探和采矿工程是一个巨大的挑战，而微波辅助岩石破碎技术则提供了有希望的解决方案。但是，由于缺乏对微波辐照对坚硬岩石的影响的知识，限制了该技术的进一步发展。已经进行了实验室测试以研究经受微波加热的花岗岩的断裂特性的变化。准备了半圆形弯曲（SCB）试样，并在经过微波处理的花岗岩试样上进行了I型断裂试验。记录声发射（AE）事件，并通过数字图像相关（DIC）技术计算应变场。测试结果表明，样品表面的温度随着加热时间的增加而线性增加，微波功率的增加有助于提高加热速率。根据扫描电子显微镜（SEM）的结果，晶间裂纹是裂纹的主要形式，而跨晶裂纹通常出现在微波功率较高或加热时间较长的样品中。微裂纹的产生可以归因于高温和热冲击。随着加热时间的增加，断裂韧性呈指数下降，AE活性期延长，断裂面的分形维数（FSD）连续增大。与未处理的样品相比，在相同的载荷水平下，微波加热样品的最大主应变和断裂过程区（FPZ）尺寸更大，这表明延展性得到了增强。根据实验结果，FPZ尺寸，断裂韧性和FSD之间的关系根据经验进行了回归。了解微波加热对断裂性能的影响对于提高硬岩破碎效率具有重要意义。