Mechanical behavior of granite subjected to thermal treatment: insight from experiment and numerical simulation

The effect of high temperature on the mechanical performance of granite is a key problem in many underground projects such as dry-hot rock mining and high-level radioactive nuclear waste disposal. In view of this, a coupled thermal-mechanical numerical model of granite is established in the present study by combining CT reconstruction technology with the discrete element GBM method. The study reproduces the real microstructure of two-dimensional scan slices of granite and considers the non-uniform heat transfer characteristics of diagenetic minerals. The numerical model can effectively depict the propagation law of microcracks between different minerals, between the same mineral, and within the same minerals after heating. The proposed model successfully simulates the strength characteristics, deformation behavior, and failure mode of granite after thermal treatment at different temperatures, thus proving the applicability of the modeling method in the study of thermal-mechanical modeling of granite. The simulation results show that granite suffers heat damage mostly in the form of tensile cracks at all the target temperatures of thermal treatment. With the increase in the temperature, the axial stress threshold of micro-cracks in granite under uniaxial load gradually decreases, and the overall fracture degree of the specimen increases. The stress-strain curve shows a post-peak decreasing trend of brittleness and an increasing trend of ductility. When the heating temperature exceeds 450celcius, thermal damage begins to dominate the final failure mode of granite. The findings of the study can provide valuable theoretical support for geotechnical engineering involving the thermodynamic properties of rocks. They can further provide a reference for numerical simulation methods for accurate characterization of the microstructure of rock.

Automated summary

In this study, a numerical model was established to investigate the effect of high temperature on the mechanical performance of granite. The results showed that granite mainly suffered heat damage in the form of tensile cracks. With the increase in temperature, the degree of fracture in granite increased, exhibiting a post-peak decrease in brittleness and an increase in ductility. When the heating temperature exceeded 450°C, thermal damage began to dominate the failure mode of granite.