Paper contribution

Mode I Fracture Toughness Tests of Limestone under High-Temperature Isothermal Condition

Jordi Delgado-Martín; Yan Li; Miguel Herbón-Penabad; Andrea Muñoz-Ibáñez

Proceedings
EUROCK 2026
Pages
459-464
Submitted
28 January 2026
Accepted
15 June 2026
Published
12 August 2026

Summary

Abstract

Understanding the fracture behavior of granite under high temperatures is crucial for assessing the stability and safety of deep geological engineering projects, such as enhanced geothermal systems (EGS), nuclear waste repositories, and deep mining. High temperatures alter the microstructure, crack propagation, and mechanical integrity of granite, thereby affecting its fracture toughness and overall durability. Although numerous studies have investigated the mechanical and thermal properties of rocks after high-temperature treatment, experimental data obtained under isothermal high temperature conditions remain limited. In this study, an improved pseudo-compact tension (pCT) testing apparatus is presented, which enables pure tension fracture testing of rock specimens under specified thermo-mechanical conditions. The system allows precise control of both temperature and mechanical loading, making it possible to monitor the fracture process directly under elevated temperatures. For the tests presented, the temperature was increased at a rate of 5 °C/min to target values of 50, 100, 150, 200, 250, 300, and 350 °C. These relatively small temperature intervals are designed to capture the gradual influence of thermal variation on the fracture characteristics of granite. The results were compared with those obtained from thermally treated granite specimens, which followed a different thermal stress path: heating to the target temperature, naturally cooling back to room temperature, and testing afterwards. The results show that, under isothermal high-temperature conditions, the mode I fracture toughness of granite increases with temperature within the studied range. In contrast, for thermally treated specimens, fracture toughness decreases with increasing treatment temperature. This opposite trend indicates that the thermal stress path affects the initiation, accumulation, and propagation of microcracks in granite, which in turn control its fracture toughness.

Contributors

Authors

  1. Jordi Delgado-Martín Universidade da Coruña, Spain
  2. Yan Li Universidade da Coruña, Spain ORCID 0000-0001-8986-3387
  3. Miguel Herbón-Penabad Universidade da Coruña, Spain ORCID 0000-0002-4818-3964
  4. Andrea Muñoz-Ibáñez Universidade da Coruña, Spain

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References

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