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<p>Existing temperature schemes of thermal damage approach assisting rock-breaking in hard rock tunnels lack sufficient mechanistic explanation and validation. This study focuses on thermal damage of granite from the Gangdese orogenic belt. A grain-based model was established to simulate the damage behavior of granite sample subjected to single heating–cooling treatment through finite-discrete element method, and the mesoscopic damage distribution was investigated. Furthermore, the development mechanisms and laws of intergranular and intragranular cracks during heating were revealed by constructing simplified physical models for the mechanical behavior of grains, and the cracking mechanisms during cooling were also analyzed. Besides, an improved thermal Preisach–Mayergoyz (PM) model was proposed to quantitatively describe strain evolution during the heating–cooling process. Finally, uniaxial compression experiments on rocks were performed to study the impact of heating amplitude and repetitive heating strategies on rock damage. The results show that thermal damage-induced intragranular cracks are mainly distributed in feldspar because of its large proportion in granite and relatively low grain strength. The differences between grains in expansion coefficients <i>α</i> and elastic modulus <i>E</i> easily lead to intergranular cracks, with the maximum shear stress distributed at the edges of grain contact surfaces. This value increases at a decelerating rate as the size ratio between feldspar grain and quartz grain in the shear direction increases. Compared to the cooling stage, damage during the heating stage is more significant. Additionally, the accuracy of the proposed thermal PM model was validated against experimental temperature–strain curves, and the model aligns with the rock’s thermal response characteristics. As the temperature rises, rock damage increases in a trend of acceleration–deceleration, with 600°C being the approximate transition point. When subjected to repeated heating, the rock exhibits a thermal felicity effect, and the growth rate of cumulative damage significantly slows down when the number of cycles exceeds six. Therefore, heating–cooling cycles not exceeding six at 600°C are recommended as the proper temperature scheme for thermally assisted rock-breaking. The specific number of cycles can be determined based on actual rock-breaking effectiveness and economic considerations.</p>

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Response of Hard Rock to Heating–Cooling Treatment and Optimal Temperature Scheme for Assisting Rock-Breaking

  • 期刊论文

  • 发表日期：

    2025年10月22日

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  • Jie Li,
  • Pengchuxuan Xu,
  • Yalong Jiang,
  • Helin Fu

摘要

Existing temperature schemes of thermal damage approach assisting rock-breaking in hard rock tunnels lack sufficient mechanistic explanation and validation. This study focuses on thermal damage of granite from the Gangdese orogenic belt. A grain-based model was established to simulate the damage behavior of granite sample subjected to single heating–cooling treatment through finite-discrete element method, and the mesoscopic damage distribution was investigated. Furthermore, the development mechanisms and laws of intergranular and intragranular cracks during heating were revealed by constructing simplified physical models for the mechanical behavior of grains, and the cracking mechanisms during cooling were also analyzed. Besides, an improved thermal Preisach–Mayergoyz (PM) model was proposed to quantitatively describe strain evolution during the heating–cooling process. Finally, uniaxial compression experiments on rocks were performed to study the impact of heating amplitude and repetitive heating strategies on rock damage. The results show that thermal damage-induced intragranular cracks are mainly distributed in feldspar because of its large proportion in granite and relatively low grain strength. The differences between grains in expansion coefficients α and elastic modulus E easily lead to intergranular cracks, with the maximum shear stress distributed at the edges of grain contact surfaces. This value increases at a decelerating rate as the size ratio between feldspar grain and quartz grain in the shear direction increases. Compared to the cooling stage, damage during the heating stage is more significant. Additionally, the accuracy of the proposed thermal PM model was validated against experimental temperature–strain curves, and the model aligns with the rock’s thermal response characteristics. As the temperature rises, rock damage increases in a trend of acceleration–deceleration, with 600°C being the approximate transition point. When subjected to repeated heating, the rock exhibits a thermal felicity effect, and the growth rate of cumulative damage significantly slows down when the number of cycles exceeds six. Therefore, heating–cooling cycles not exceeding six at 600°C are recommended as the proper temperature scheme for thermally assisted rock-breaking. The specific number of cycles can be determined based on actual rock-breaking effectiveness and economic considerations.