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ORIGINAL PAPER

Experiment study of physical and mechanical properties of sandstone after variable thermal cycles Qiang Sun 1,2 & Jishi Geng 1,2,3 & Fei Zhao 1,2,3 Received: 28 November 2019 / Accepted: 15 March 2020 # Springer-Verlag GmbH Germany, part of Springer Nature 2020

Abstract To study the effects of temperature cycles on the mechanical properties, thermal damage, and fracturing of sandstone, uniaxial compression tests and Brazilian splitting tests were performed using a hydraulic pressure servo rigidity rock mechanics experiment system. Before the tests, the sandstone samples were treated with cyclic (repeated from 0 to 8 cycles) temperatures from 100 to 600 °C. In addition, the chromaticity (color parameters L*, a*, and b*), thermal conductivity, and P wave velocity of the sandstone samples were measured using a color meter, thermal conductivity tester, and acoustic wave detection device, respectively. The results show that the peak strength, tensile strength, thermal conductivity, and P wave velocity decrease rapidly when the samples are exposed to higher temperatures (> 400 °C). Below 300 °C, the decrease is mainly due to the escaping of the adhered, bound, and structural water. Between 300 and 600 °C, the thermal response of the minerals in sandstone increases the development of microcracks and weakens the sandstone. At these same temperatures, when the number of cycles increases, the peak strength and tensile strength of the sandstone decrease, which is more obvious at higher temperatures. After multiple cycles, the plastic characteristics of the sandstone increase. The results obtained in this paper are good for predicting the thermo-physical properties of sandstone when exposed to high temperatures. Keywords Sandstone . Thermal cycle . Physical and mechanical properties

Introduction Underground rock mass may be subjected to high temperatures during its diagenesis and artificial excavation. This includes geological engineering, mines, geothermal resource

* Jishi Geng [email protected] * Fei Zhao [email protected] Qiang Sun [email protected] 1

Geological Research Institute for Coal Green Mining, Xi’an University of Science and Technology, Xi’an, Shaanxi Province 710054, People’s Republic of China

2

College of Geology and Environment, Xi’an University of Science and Technology, Xi’an, Shaanxi Province 710054, People’s Republic of China

3

School of Resources and Geosciences, China University of Mining and Technology, Xuzhou, Jiangsu Province 221116, People’s Republic of China

development, coal seam gas safety and comprehensive utilization, deep underground nuclear waste disposal, and the restoration and reconstruction of underground rock caverns after the fires, which involves the mechanical properties of rock under the effects of high temperatures (Somerton and Gupta 1965; Fridleifsson 2001; Ranjith et al. 2012; Kovačević et al. 2013; Hong et al. 2015; Sun et al. 2015; Gautam et al. 2016; Geng et al. 2018). It is important to establish the situations that stonework can be resto