School of Mines, China University of Mining and Technology, Xuzhou, Jiangsu Province, China.
School of Transportation Engineering, Jiangsu Vocational Institute of Architectural Technology, Xuzhou, Jiangsu Province, China.
PLoS One. 2024 Nov 1;19(11):e0312460. doi: 10.1371/journal.pone.0312460. eCollection 2024.
Investigating the coupling effects of temperature levels and heating-water cooling cycles on the physical and mechanical responses of HDR (hot dry rock) is a vital issue during the exploitation of geothermal energy. In this study, the physical properties of granite specimens were measured first after each heating and water-cooling cycle. Then, uniaxial compressive tests were conducted on those granites to obtain their mechanical properties. With the increase in heating temperature (T) and cycles of heating and water cooling (N), P-wave velocity, uniaxial compression strength (UCS), and elastic modulus (E) showed a decreasing tendency, and the decrease of those four properties corresponding to T variation is greater than N variation. Due to the α-β phase transition of quartz happening at 573°C, the density UCS and E of granite decreased rapidly when the heating temperature increased from 450°C to 600°C at N = 1. With the increase of T and N, the failure mode of granite gradually changes from tensile failure to shear failure and, finally, comminute failure. The failure mechanism of granite gradually transfers from brittleness-dominated to ductility-dominated due to accumulated thermal damage. Finally, X-ray diffraction (XRD) and scanning electron microscope (SEM) were used to determine the damage mechanism of cyclic heating-cooling. The micro test results show that the high-temperature treatment changes the mineral composition and the microcracks number of the granite and finally affects the macroscopic physical and mechanical properties. The study conclusions of this manuscript are important for exploiting geothermal resources.
研究温度水平和加热-水冷却循环对 HDR（高温干热岩）物理力学响应的耦合效应是开发地热能过程中的一个重要问题。在本研究中，首先测量了每个加热和水冷却循环后的花岗岩试件的物理性质，然后对这些花岗岩进行单轴压缩试验以获得它们的力学性质。随着加热温度（T）和加热-水冷却循环次数（N）的增加，P 波速度、单轴抗压强度（UCS）和弹性模量（E）呈下降趋势，这四个性质对应于 T 变化的减少大于 N 变化的减少。由于石英的α-β相转变发生在 573°C，因此当加热温度从 450°C 增加到 600°C 时，在 N = 1 的情况下，花岗岩的密度、UCS 和 E 会迅速下降。随着 T 和 N 的增加，花岗岩的破坏模式逐渐从拉伸破坏转变为剪切破坏，最后转变为粉碎破坏。由于热损伤的累积，花岗岩的破坏机制逐渐从脆性主导转变为延性主导。最后，使用 X 射线衍射（XRD）和扫描电子显微镜（SEM）来确定循环加热-冷却的损伤机制。微观测试结果表明，高温处理改变了花岗岩的矿物组成和微裂纹数量，最终影响了宏观物理力学性能。本文的研究结论对开发地热能资源具有重要意义。
