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<p>Efficient deep drilling under high in situ stresses is essential to meet rising global energy demands, yet it remains hindered by rapidly increasing rock strength and tool wear. Thermally assisted drilling, by inducing microcracks through controlled heating, offers a promising route to weaken rock prior to mechanical excavation, but the coupled evolution of thermal and mechanical energy during fracture is not fully understood. In this work, a grain-based model (GBM) of Lac du Bonnet (LdB) granite is reconstructed and subjected to uniaxial compression simulations at temperatures from ambient up to 600&#xa0;°C. We show that thermal cracks nucleate preferentially at mineral interfaces with contrasting expansion coefficients and coalesce into complex networks as temperature rises. Elastic strain energy during heating follows four distinct stages: rapid rise, gradual increase, plateau, and decline; subsequent mechanical loading exhibits reduced peak strength and increasingly ductile failure dominated by thermal damage. Notably, in the 200–400&#xa0;°C range, the pre-existing thermal crack network lowers the total energy required for catastrophic failure, owing to competitive interactions between grain boundaries and microcracks. These findings establish a coupled thermo-mechanical energy–fracture framework that clarifies fundamental damage mechanisms and offer guidelines for optimizing thermal pre‑treatment parameters in field‑scale assisted drilling applications.</p>

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Energy Partitioning Evolution and Crack Interaction in Granite Under Sequential Thermal and Mechanical Loading

  • 期刊论文

  • 发表日期：

    2025年10月9日

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  • Jiming Li,
  • Jianming Peng,
  • P. G. Ranjith,
  • Yanliang Li

摘要

Efficient deep drilling under high in situ stresses is essential to meet rising global energy demands, yet it remains hindered by rapidly increasing rock strength and tool wear. Thermally assisted drilling, by inducing microcracks through controlled heating, offers a promising route to weaken rock prior to mechanical excavation, but the coupled evolution of thermal and mechanical energy during fracture is not fully understood. In this work, a grain-based model (GBM) of Lac du Bonnet (LdB) granite is reconstructed and subjected to uniaxial compression simulations at temperatures from ambient up to 600 °C. We show that thermal cracks nucleate preferentially at mineral interfaces with contrasting expansion coefficients and coalesce into complex networks as temperature rises. Elastic strain energy during heating follows four distinct stages: rapid rise, gradual increase, plateau, and decline; subsequent mechanical loading exhibits reduced peak strength and increasingly ductile failure dominated by thermal damage. Notably, in the 200–400 °C range, the pre-existing thermal crack network lowers the total energy required for catastrophic failure, owing to competitive interactions between grain boundaries and microcracks. These findings establish a coupled thermo-mechanical energy–fracture framework that clarifies fundamental damage mechanisms and offer guidelines for optimizing thermal pre‑treatment parameters in field‑scale assisted drilling applications.