Geomechanical properties of rocks change considerably when subjected to thermal loading. In some cases, the damage induced by thermal loading is advantageous for geotechnical activities such as geothermal reservoir and hydraulic fracturing, and it is non-beneficial for other activities including stability of underground spaces and rock slopes; therefore, this paper deals with parameters such as P-wave form and power spectral density (PSD) as indexes for considering the degree of damage induced by thermal loading in rocks. In this regard, 7 types of rocks in 3 categories including igneous, sedimentary, and metamorphic were selected and heated up to 500 °C at furnace for 5 h; then, the specimens were cooled down immediately, and subsequently, P-wave velocity and P-wave form were measured. The results showed that thermal loading has no significant impact on the frequency component of different rocks; however, PSD parameter decreases dramatically after heating at 500 °C. In addition, the effect of thermal loading at 500 °C on the P-wave form for crystalline and non-crystalline rocks is variable. For crystalline rocks at room temperature, the peak of PSD parameter reduces more than non-crystalline rocks; in other words, in crystalline rocks, the dissipation of energy is greater than non-crystalline rocks. Microscopic observations were also provided in order to investigate the effect of thermal loading on PSD parameter in detail. It can be concluded that the mechanism of intergranular and intragranular microcracks in crystalline rocks and also the mechanism of disintegrated background cement in non-crystalline rocks could be attributed to the reduction in peak of PSD parameter.

中文翻译：

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热载荷对晶体和非晶体岩石中P波形和功率谱密度的影响

岩石在受热负荷时的地质力学性质会发生很大变化。在某些情况下，热负荷引起的破坏对岩土活动（例如地热储层和水力压裂）有利，而对其他活动（包括地下空间和岩石边坡的稳定性）则无益。因此，本文将P波形和功率谱密度（PSD）等参数作为考虑岩石热载荷引起的破坏程度的指标。因此，选择了火成岩，沉积岩和变质岩这三类中的七种岩石，并在炉中加热到500°C加热了5小时。然后，将样品立即冷却，随后测量P波速度和P波形式。结果表明，热负荷对不同岩石的频率分量没有显着影响。但是，在500°C加热后，PSD参数急剧下降。此外，在500°C的热负荷对晶体和非晶体岩石的P波形式的影响是可变的。对于室温下的结晶岩，PSD参数的峰值比非结晶岩减小更多；反之，换句话说，在晶体岩石中，能量耗散大于非晶体岩石。还提供了显微镜观察，以便详细研究热负荷对PSD参数的影响。