Thermal loading effect on P-wave form and power spectral density in crystalline and non-crystalline rocks
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ORIGINAL PAPER
Thermal loading effect on P-wave form and power spectral density in crystalline and non-crystalline rocks Bijan Dehghani 1 & Vahid Amirkiyaei 1 & Reza Ebrahimi 2 & Habib Ahmadi 1 & Danial Mohammadzamani 1 & Saeed Beheshti Zavareh 1 Received: 29 February 2020 / Accepted: 29 July 2020 # Saudi Society for Geosciences 2020
Abstract 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 nonbeneficial 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. Keywords Power spectral density . P-wave form . Crystalline rocks . Non-crystalline rocks . Thermal loading
Responsible Editor: Zeynal Abiddin Erguler
Introduction
* Bijan Dehghani [email protected]
The effect of thermal loading on physical and mechanical properties of rocks has the most extensive application in rock mechanics such as hydraulic fracturing in petroleum and geothermal reservoir in order to enhance permeability, stability of deep underground spaces and petroleum wells, durability and strength of building stones in different climate conditions, intensification of rock burst phenomenon, and rock fragmentation in terms of mineral processing (Chen et al. 2014a; Kim et al. 2014; Zhang et al. 2015; Gautam et al. 2016; Peng et al. 2016; Zhang 2016; Kumari et al. 2017). The impact of thermal loading on the physical and mechanical properties of rocks has been investigated by many researchers (Shao et al. 2014; Liu and Xu 2015; Li et al. 2016; Wang et al. 2016a, b; Chen et al. 2017b; Yang et al
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