岩石破碎是隧道开挖不可回避的工作，选择破岩方法应以快速、高效为原则。机械破岩是目前的主要方法之一，但是对于强度较大的硬岩层和特硬岩层，机械破岩刀具往往磨损过快，缺乏经济上的竞争力。如果在机械破碎之前，预先使用微波照射以降低硬岩强度，将极大提高破岩效率，故 “微波+机械”组合能量切岩、破岩系统将成为一种重要的隧道开挖新技术。 本文依据微波加热和岩石热破裂的基本理论，在试验的基础上，寻求建立有效的岩石数值模型，采用数值模拟方法对微波照射损伤岩石进行研究，分析岩石损伤的细观力学机理，得到损伤的规律。具体研究内容及结论如下： （1）从岩石热破裂理论对微波照射岩石造成强度损伤的原理进行理论分析，认为微波照射对岩石强度的损伤主要是由岩石内部不同矿物的性质差异引起。在照射中，性质差异造成岩石内温度不平衡，形成“热点”，再由于不同矿物热膨胀系数差异，造成膨胀差异引发热应力，当热应力大于岩石强度时就引发岩石损伤，强度降低。 （2）试验施加不同功率和照射时间的微波作用，得到岩石强度损伤规律：照射时间一定的条件下，岩石损伤程度与微波功率呈正相关；微波功率一定的情况下，存在一个最佳的照射时间范围，在此时间范围内，照射时间增加将有效地造成损伤，降低强度。此后增加照射时间将不能有效提高损伤程度。 （3）依据试验研究，利用有限元软件ANSYS建立类似花岗岩的二相岩石模型，通过模拟微波照射得到岩石内部温度场、应力场和塑性破坏的发展演化规律，分析岩石破坏的细观机理和不同条件下的损伤规律，认为岩石损伤主要由拉应力破坏和剪切破坏两方面造成，功率密度越高对损伤越有利。高功率微波作用下的岩石破坏趋向于拉应力破坏，低功率情况下则主要为剪切破坏。在一定时间以内，照射时间与损伤呈正相关。数值研究结论与试验结论相一致，验证了模拟的正确性。 通过本文研究，深刻了解微波照射损伤岩石的机理和规律，对今后的研究奠定了基础，促进了“微波+机械”组合能量隧道掘进破岩技术的发展。

Rock breaking is one of the inevitable jobs in tunnel excavation. Choosing a suitable method of rock damage should be in a quick and efficient for the principle. Mechanical rock fragmentation is the main method currently. However, mechanical rock cutting tools often wear too fast, so it is lack of economic competitiveness. Taking microwave irradiation before mechanical crushing, reducing the intensity of hard rock in advance, will greatly improve the efficiency of rock fragmentation. So it will become an important tunnel excavation mean by adopting the method of “microwave & machine" integrated energy rock cutting. In this paper, according to the basic theory of microwave heating and rock thermal fracturing, an effective numerical model of rock will be built based on experiment research. Through the method of numerical simulation, microscopic mechanism and laws of microwave induced rock damage will be caught. Specific research contents and conclusions are as follows: (1) Based on the rock thermal cracking theory, the principle of rock damage induced by microwave irradiation has been analyzed. It shows that the principle of microwave irradiation on rock strength weakening was thought to be mainly caused by the differences of property of minerals in rock. Under irradiation, different minerals properties make temperature in rock unbalanced，“hot spot” will be made. Additionally, differences of thermal expansion coefficient of minerals leads to different inflation and causes thermal stress. When the thermal stress is greater than the rock strength, it will induce rock damage. Rock strength will be reduced. (2) In experiment, through applying microwave irradiation by different microwave power and irradiation time, the law of rock damage is got. It shows that microwave power is positively correlated with rock damage under the certain irradiation time. Under the certain power, there is an optimal range of irradiation time, in this time range, increasing irradiation time can make damage effectively, and reduce the rock strength. Increasing irradiation time after this time range will not be able to improve the rock damage degree. (3) Based on experiment study, through the establishment of simplified model of two phase rock by using finite element software ANSYS, the temperature field，stress field and the rules of the development of plastic failure is obtained by simulation. The failure mechanism and the damage laws on different conditions are analyzed. Study shows that rock damage is mainly caused by two aspects of tensile stress damage and shear failure. The higher power density can be reached, the better for rock damage. Higher power density mainly makes more tensile stress damage, lower power density makes more shear failure. Within a certain time, irradiation time and damage are positively correlated. Conclusion of numerical research is consistent with the test results, so the correctness of the simulation is verified. Through this paper research, mechanism and law of rock damage by microwave irradiation has been caught. It settles the foundation for future research. Promoting the development of "microwave & mechanical" combined energy tunnel excavation technology.