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<p>Evaluating rock properties under different thermal treatments has gained substantial attention in the last few decades concerning its implication in various sub-surface rock engineering applications. Although basaltic rock masses are frequently subjected to high temperatures, the impact of thermal damage, especially under rapid cooling with liquid nitrogen, has received relatively little attention over the years. This study investigates these effects by analyzing changes in effective porosity, ultrasonic wave velocities, Brazilian tensile strength index (BTS), and microstructure following thermal treatment, where specimens were heated at 100–800&#xa0;°C, followed by immediate cooling with atmospheric air for one cycle (AC-1), liquid nitrogen (LN<sub>2</sub>) for one cycle (LN<sub>2</sub>C-1) and five cycles (LN<sub>2</sub>C-5). Broadly, AC-1 and LN<sub>2</sub>C-1 show decreased porosity, minimal change in ultrasonic velocities, and higher BTS values at ≤ 200&#xa0;°C, while LN<sub>2</sub>C-5 shows similar behavior at ≤ 100&#xa0;°C. This could be attributed to dehydration and thermal expansion, which lead to pore closure and the formation of a more compact structure. Between 200 and 600&#xa0;°C in AC-1 and LN<sub>2</sub>C-1 and 100&#xa0;°C–600&#xa0;°C in LN<sub>2</sub>C-5, effective porosity and damage coefficients gradually increase, while BTS decreases. From 600 to 800&#xa0;°C, rock properties change more rapidly, primarily due to the formation and propagation of thermal microcracks that weaken the grain bonding. These trends were supported by microstructural analysis. Given the frequent exploration of basaltic terrains for geothermal energy, thermal energy storage, and other underground rock engineering projects, the findings of this study will help optimize drilling parameters and build the sustainable design of rock structures.</p>

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Effect of heating-liquid nitrogen cooling cycles on the physical properties and tensile strength of basalt

  • 期刊论文

  • 发表日期：

    2025年11月24日

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  • Bikash Kumar Ram,
  • Rajeswar Das,
  • Deepak Amban Mishra,
  • Ranjan Pramanik,
  • Himangshu Kakati,
  • Rajat Jain

摘要

Evaluating rock properties under different thermal treatments has gained substantial attention in the last few decades concerning its implication in various sub-surface rock engineering applications. Although basaltic rock masses are frequently subjected to high temperatures, the impact of thermal damage, especially under rapid cooling with liquid nitrogen, has received relatively little attention over the years. This study investigates these effects by analyzing changes in effective porosity, ultrasonic wave velocities, Brazilian tensile strength index (BTS), and microstructure following thermal treatment, where specimens were heated at 100–800 °C, followed by immediate cooling with atmospheric air for one cycle (AC-1), liquid nitrogen (LN2) for one cycle (LN2C-1) and five cycles (LN2C-5). Broadly, AC-1 and LN2C-1 show decreased porosity, minimal change in ultrasonic velocities, and higher BTS values at ≤ 200 °C, while LN2C-5 shows similar behavior at ≤ 100 °C. This could be attributed to dehydration and thermal expansion, which lead to pore closure and the formation of a more compact structure. Between 200 and 600 °C in AC-1 and LN2C-1 and 100 °C–600 °C in LN2C-5, effective porosity and damage coefficients gradually increase, while BTS decreases. From 600 to 800 °C, rock properties change more rapidly, primarily due to the formation and propagation of thermal microcracks that weaken the grain bonding. These trends were supported by microstructural analysis. Given the frequent exploration of basaltic terrains for geothermal energy, thermal energy storage, and other underground rock engineering projects, the findings of this study will help optimize drilling parameters and build the sustainable design of rock structures.