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<p>The utilization of seawater as a heat exchange fluid presents a novel concept for the exploitation of geothermal energy in hot dry rock formations in coastal regions. The cyclic load resulting from the excavation and hydraulic fracturing processes will exacerbate the thermal damage associated with high-temperature geological engineering. This study investigates the deformation behavior, mechanical response characteristics, and energy evolution mechanisms of granite subjected to thermal damage (25–1000&#xa0;°C) followed by seawater cooling under triaxial multistage cyclic loading. The stress–strain curves, volume and stiffness changes, energy conversion, and failure modes of the rock are analyzed. Results demonstrate that the microcracks are primarily attributable to thermal damage. As the thermal shock temperature increases, the compressive strength and elastic modulus of granite initially increase before subsequently decreasing, reaching a maximum at 400&#xa0;°C, with increases of 15.34% and 9.53%, respectively, and decreases of 15.05% and 54.38%, respectively, at 1000&#xa0;°C, compared to natural granite. Conversely, irreversible deformation initially decreases before subsequently increasing. Failure mode transitions from a typical shear brittle failure to a plastic rheological failure. Microstructural analysis reveals significant porosity development, escalating from 0.013% in natural granite to 2.554% following 1000&#xa0;°C thermal shock. Thermal shock reduces the crack damage threshold of the granite, beyond which the energy storage coefficient begins to decrease.</p>

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Mechanical Properties and Energy Evolution of Granite to Cyclic Loading Under Thermal Shock and Seawater Coupling

  • 期刊论文

  • 发表日期：

    2025年9月1日

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  • Wenfeng Shen,
  • Wei Wang,
  • Xuelei Duan,
  • Yajun Cao,
  • Yun Jia,
  • Qizhi Zhu

摘要

The utilization of seawater as a heat exchange fluid presents a novel concept for the exploitation of geothermal energy in hot dry rock formations in coastal regions. The cyclic load resulting from the excavation and hydraulic fracturing processes will exacerbate the thermal damage associated with high-temperature geological engineering. This study investigates the deformation behavior, mechanical response characteristics, and energy evolution mechanisms of granite subjected to thermal damage (25–1000 °C) followed by seawater cooling under triaxial multistage cyclic loading. The stress–strain curves, volume and stiffness changes, energy conversion, and failure modes of the rock are analyzed. Results demonstrate that the microcracks are primarily attributable to thermal damage. As the thermal shock temperature increases, the compressive strength and elastic modulus of granite initially increase before subsequently decreasing, reaching a maximum at 400 °C, with increases of 15.34% and 9.53%, respectively, and decreases of 15.05% and 54.38%, respectively, at 1000 °C, compared to natural granite. Conversely, irreversible deformation initially decreases before subsequently increasing. Failure mode transitions from a typical shear brittle failure to a plastic rheological failure. Microstructural analysis reveals significant porosity development, escalating from 0.013% in natural granite to 2.554% following 1000 °C thermal shock. Thermal shock reduces the crack damage threshold of the granite, beyond which the energy storage coefficient begins to decrease.