Microwave heating is a promising technique in assisting the breakage of hard and abrasive rocks. It features rapid heating and selective heating, enabling generation of large enough thermal stresses to induce damage in rocks. This paper investigated the effect of microwave treatment on the heating rate, spatial temperature distribution, ultrasonic wave velocity, elastic modulus and load bearing capacity of three igneous rocks (i.e., gabbro, monzonite and granite). The crack pattern and crack density were also studied using petrographic thin-section observations. Experimental results indicate that the single-mode microwave system can effectively and efficiently weaken the three rocks by generating cracks or melting/shattering the specimens. The heating rates and thermal gradients increase as either exposure time or power level increases. When heated at 2 kW for 120 s, the P-wave velocities of gabbro and monzonite can be reduced to 44% and 51%, respectively, S-wave velocities reduced to 34% and 62%, Young’s modulus reduced to 13% and 27%, load bearing capacity reduced to 34% and 43%. In contrast, granite specimens were more prone to violent failures at high power levels. Petrographic observations imply that the dominant crack types in gabbro, monzonite and granite are intergranular & transgranular cracks, intergranular cracks, and transgranular cracks, respectively.

中文翻译：

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微波处理下三种火成岩的热力学行为和开裂行为的试验研究

微波加热是一种有助于破碎坚硬和磨蚀性岩石的有前途的技术。它具有快速加热和选择性加热的特点，能够产生足够大的热应力，从而导致岩石损坏。本文研究了微波处理对三种火成岩（即辉长岩、二长岩和花岗岩）的加热速率、空间温度分布、超声波速度、弹性模量和承载能力的影响。裂纹模式和裂纹密度也使用岩相薄片观察进行了研究。实验结果表明，单模微波系统可以通过产生裂缝或熔化/破碎试样来有效地削弱三块岩石。加热速率和热梯度随着暴露时间或功率水平的增加而增加。2 kW加热120 s时，辉长岩和二长岩的纵波速度分别降低到44%和51%，横波速度分别下降到34%和62%，杨氏模量分别下降到13%和27 %，承载能力降低到 34% 和 43%。相比之下，花岗岩标本在高功率水平下更容易发生剧烈故障。岩相学观察表明辉长岩、二长岩和花岗岩中的主要裂缝类型分别是晶间和穿晶裂缝、晶间裂缝和穿晶裂缝。花岗岩标本在高功率水平下更容易发生剧烈故障。岩相学观察表明辉长岩、二长岩和花岗岩中的主要裂缝类型分别是晶间和穿晶裂缝、晶间裂缝和穿晶裂缝。花岗岩标本在高功率水平下更容易发生剧烈故障。岩相学观察表明辉长岩、二长岩和花岗岩中的主要裂缝类型分别是晶间和穿晶裂缝、晶间裂缝和穿晶裂缝。