<p>隧道掘进过程中，微波照射技术能够有效引起岩石内部热损伤，诱发微裂纹的萌生和扩展，从而降低施工难度并提高破岩效率。高功率微波照射后工作面环境温度过高，不利于机械和工作人员的安全，而低功率循环照射不仅可以满足致裂要求，还能降低工作面施工温度，因此开展低功率循环照射对岩石损伤效应的研究具有重要理论意义和应用价值。首先，对微波作用下的花岗岩致裂机理以及损伤特性进行分析；其次，研究了不同微波功率、循环次数、冷却方式下花岗岩的升温特性、纵波波速以及宏观力学性能的变化规律，从宏细观层面揭示了微波循环照射花岗岩的损伤机制和破坏机理；最后，基于损伤力学理论与岩石本构理论，建立了考虑多因素耦合作用的花岗岩损伤本构模型。主要研究成果和内容如下：</p> <p>（1）随着微波功率的增大，花岗岩试样最终表面温度不断升高，纵波波速下降速率越快；相同微波功率照射时，试样纵波波速随着加热次数的增多而不断减小；相同微波作用下，冲水冷却方式下试样的纵波波速下降程度高于自然冷却方式，这是微波照射和水冷却共同作用的结果。</p> <p>（2）对花岗岩断口形貌进行微观试验，分析了微波功率和照射次数对花岗岩断口处裂纹形态及发育特征的影响。发现试样断口形貌的裂纹形式有沿晶裂纹、穿晶裂纹和晶内裂纹；裂纹的开度、数量、密度均与微波功率和加热次数有关，且随着微波功率和加热次数的增加，裂纹发育程度越高。</p> <p>（3）对微波照射后的花岗岩进行准静态单轴压缩试验。随着微波功率和照射次数的增加，应力-应变曲线逐渐向右下方移动；微波照射后花岗岩的力学性能均出现不同程度的降低，其中峰值应力和弹性模量降低，峰值应变增大，破坏时碎块弹射能力降低，破碎程度加剧；冲水冷却方式对试样破坏程度产生一定影响，但影响程度远低于照射次数。</p> <p>（4）采用不同方法对微波照射花岗岩损伤特性进行分析，损伤因子随着微波参数和加热次数的增加呈正相关规律变化；基于应变等效原理，推导了考虑多因素影响的花岗岩损伤变量，并对试样加载初期的孔隙闭合特征进行表征，建立了考虑微波效应的花岗岩损伤本构模型，对模型参数进行确定，并将理论曲线与试验曲线对比，验证了本构模型的可靠性。</p> <p>本文主要对低功率微波循环照射引起的岩石力学性能和损伤特性进行了尝试性探索，总结了岩石损伤与微波功率、循环照射之间的规律变化，对微波辅助破岩技术的发展起到了促进作用，与此同时，为今后的工程开展提供理论依据和参考。</p>

<p>In the process of tunnel excavation, microwave irradiation technology can effectively cause thermal damage inside the rock, induce the initiation and propagation of micro cracks, so as to reduce the difficulty of construction and improve the efficiency of rock breaking. The environmental temperature of the working face is too high after high power microwave irradiation, which is not conducive to the safety of machinery and workers. Low power cyclic irradiation can not only meet the requirements of cracking, but also reduce the construction temperature of the working face. Therefore, it is of great theoretical significance and application value to study the effect of low power cyclic irradiation on rock damage. Firstly, the fracture mechanism and damage characteristics of granite under microwave are analyzed; Secondly, the variation laws of temperature rise characteristics, longitudinal wave velocity and macroscopic mechanical properties of granite under different microwave power, cycle times and cooling methods were studied, and the damage mechanism and failure mechanism of microwave irradiation on granite were revealed from the macro and meso levels. Finally, based on the damage mechanics theory and rock constitutive theory, the damage constitutive model of granite considering multi-factor coupling is established. The main research results and contents are as follows:</p> <p>With the increase of microwave power, the final surface temperature of granite sample increases continuously, and the decrease rate of longitudinal wave velocity is faster. When the microwave power is the same, the longitudinal wave velocity of the sample decreases with the increase of heating times. Under the same microwave effect, the decrease of the longitudinal wave velocity of the specimen under the water cooling mode is higher than that under the natural cooling mode, which is the result of the combined effect of microwave irradiation and water cooling.</p> <p>The fracture morphology of granite was microscopically tested, and the effects of microwave power and irradiation times on the crack morphology and development characteristics of granite fracture were analyzed. It was found that the crack forms of the fracture morphology of the specimen were intergranular crack, transgranular crack and intragranular crack. The opening, number and density of cracks are related to microwave power and heating times, and the degree of crack development increases with the increase of microwave power and heating times.</p> <p>Quasi-static uniaxial compression tests were carried out on granite irradiated by microwave. With the increase of microwave power and irradiation times, the stress-strain curve gradually moves to the lower right; after microwave irradiation, the mechanical properties of granite decreased to varying degrees, in which the peak stress and elastic modulus decreased, the peak strain increased, the ejection ability of fragments decreased and the fragmentation degree increased. The way of water cooling has a certain effect on the damage degree of the sample, but the effect is far less than the number of irradiation.</p> <p>The damage characteristics of granite irradiated by microwave were analyzed by different methods. The damage factor was positively correlated with the increase of microwave parameters and heating times. Based on the strain equivalence principle, the granite damage variable considering the influence of multiple factors was deduced, and the pore closure characteristics of the specimen at the initial loading stage were characterized. The granite damage constitutive model considering the microwave effect was established, and the model parameters were determined. The reliability of the constitutive model was verified by comparing the theoretical curve with the experimental curve.</p> <p>In this paper, the mechanical properties and damage characteristics of rock caused by low power microwave cyclic irradiation are tentatively explored. The regular changes between rock damage and microwave power and cyclic irradiation are summarized, which promotes the development of microwave assisted rock breaking technology. At the same time, it also provides theoretical basis and reference for future engineering development.</p>

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