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<p>Investigating rock dynamics under real-time thermo–hydro–mechanical (THM) coupling is crucial for deep underground excavation and resource development. This research employs a modified THM multi-field coupled Hopkinson bar apparatus to conduct dynamic impact tests on deep coal mine sandstone. It analyzes the dynamic mechanical properties, energy dissipation laws, and deformation characteristics of the sandstone under different temperatures (25–90&#xa0;°C), different water pressures (0–15&#xa0;MPa), and a specific in situ stress (26&#xa0;MPa). Furthermore, the principles of fractal dimension, XRD, SEM, and NMR testing are utilized to explore the damage evolution mechanism of sandstone under the combined conditions of real-time THM coupling and impact loading. The results indicate that: with temperature elevation under real-time THM conditions, sandstone undergoes sequential strengthening and weakening phases in both dynamic compressive strength and elastic modulus, suggesting that the critical temperature for the transition in the strength characteristics of sandstone under impact loading lies as <i>T</i> = 50–75&#xa0;°C. The peak dynamic strain, residual dynamic strain, and average strain rate of sandstone show strong dependence on water pressure. The mass fractal dimension is more significantly affected by water pressure than by temperature. As water pressure rises, sandstone's incident energy and energy utilization ratio both first rise and then fall, suggesting that water pressure first encourages and then limits sandstone's ability to absorb energy. Compared to <i>T</i> = 25–50&#xa0;°C, the dissolution and hydrolysis reactions of internal minerals in sandstone under high-temperature water bath conditions accelerate the weakening of its dynamic mechanical properties. High water pressure promotes a transition in the internal micromorphology of sandstone from intergranular fracture to transgranular fracture. The change in sandstone porosity is noticeably influenced by temperature. Furthermore, the <i>T</i><sub>2</sub> spectrum distribution curve of the impacted sandstone exhibits a triple-peak pattern. The high-temperature water–rock interaction, deterioration effect of pore water pressure, and thermal cracking are identified as the primary reasons for the strength attenuation of sandstone under the combined THM coupling and impact loading.</p>

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Experimental Study on Dynamic Mechanical Response Characteristics and Damage Mechanisms of Deep Sandstone Under THM Coupling

  • 期刊论文

  • 发表日期：

    2026年5月13日

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  • Bobo Zhang,
  • Qi Ping

摘要

Investigating rock dynamics under real-time thermo–hydro–mechanical (THM) coupling is crucial for deep underground excavation and resource development. This research employs a modified THM multi-field coupled Hopkinson bar apparatus to conduct dynamic impact tests on deep coal mine sandstone. It analyzes the dynamic mechanical properties, energy dissipation laws, and deformation characteristics of the sandstone under different temperatures (25–90 °C), different water pressures (0–15 MPa), and a specific in situ stress (26 MPa). Furthermore, the principles of fractal dimension, XRD, SEM, and NMR testing are utilized to explore the damage evolution mechanism of sandstone under the combined conditions of real-time THM coupling and impact loading. The results indicate that: with temperature elevation under real-time THM conditions, sandstone undergoes sequential strengthening and weakening phases in both dynamic compressive strength and elastic modulus, suggesting that the critical temperature for the transition in the strength characteristics of sandstone under impact loading lies as T = 50–75 °C. The peak dynamic strain, residual dynamic strain, and average strain rate of sandstone show strong dependence on water pressure. The mass fractal dimension is more significantly affected by water pressure than by temperature. As water pressure rises, sandstone's incident energy and energy utilization ratio both first rise and then fall, suggesting that water pressure first encourages and then limits sandstone's ability to absorb energy. Compared to T = 25–50 °C, the dissolution and hydrolysis reactions of internal minerals in sandstone under high-temperature water bath conditions accelerate the weakening of its dynamic mechanical properties. High water pressure promotes a transition in the internal micromorphology of sandstone from intergranular fracture to transgranular fracture. The change in sandstone porosity is noticeably influenced by temperature. Furthermore, the T2 spectrum distribution curve of the impacted sandstone exhibits a triple-peak pattern. The high-temperature water–rock interaction, deterioration effect of pore water pressure, and thermal cracking are identified as the primary reasons for the strength attenuation of sandstone under the combined THM coupling and impact loading.