###### Abstract  
High temperatures significantly affect the physical and mechanical properties of rocks in deep geoengineering projects, such as geothermal development, deep mining, and the geological disposal of nuclear waste. Therefore, it is essential to explore the relationship between the thermal damage (TD) of granite and its influencing factors. This paper characterizes the TD of granite specimens subjected to high temperatures of up to 800 \({}^{\circ}\)C and proposes a predictive model for this thermal damage. A database, which includes publicly available experimental data of advanced microscopic observations of granite specimens exposed to high-temperature treatments and their changes in physical and mechanical properties, was compiled and analyzed. The collected data revealed a consistent trend: crack development among quartz, feldspar, and biotite minerals was observed to intensify notably between 400 \({}^{\circ}\)C and 600 \({}^{\circ}\)C, as indicated by changes in the mechanical properties. Based on these characteristics, the relationships between TD and its influential parameters were determined using regression models and several machine learning algorithms. The derived models indicated good predictability performance with a coefficient of determination (R\({}^{2}\)) varying between 0.60 and 0.97, with the boosted ensemble tree model being the best. Nevertheless, mineral contents were not found to be good predictors of TD, even if they control the evolution of the crack during the heat treatment. It was concluded that the findings of this study could serve as a valuable tool for assessing the thermal damage of rocks. g ARTIC 2025 15 6328 +
Footnote †: journal: Applied sciences  
16 April 20251  
properties, which is a pressing concern in these engineering projects [5; 6; 7]. In essence, the weakening in macroscopic physical and mechanical properties results from changes in mineral composition and characteristics at high temperatures [8]. Different minerals expand at different rates at high temperatures, and the same mineral can expand at different rates and in many directions [6; 9; 10]. Such expansion can cause stress accumulation at the edges of minerals, damaging the structure when heated. Therefore, the heated rock may produce intergranular and intragranular microcracks among and within mineral crystals [3]. In addition to these intergranular microcracks in igneous rock, intragranular cracks in some of the weaker mineral elements, like feldspar and biotite grains, also play a role in crack propagation. High temperatures can also induce thermal reactions in minerals that form rocks, altering their composition and structure, resulting in different types of microcracks. As a result, microcrack formation brought on by heat treatment alters the physico-mechanical behaviors of rocks [11; 12; 13], which eventually impacts any rock engineering design subjected to high temperatures. Therefore, extensive research is required to fully comprehend the impact of high temperatures on rocks spanning from microscopic mineral composition to macroscopic physical and mechanical properties, including mineral composition, dehydration, crystalline state, and the formation of new phases. Motivated by this importance, extensive studies have been conducted over the past few decades, taking advantage of the availability of technologies such as scanning electron microscopy (SEM), optical microscopy, X-ray microcomputed tomography (CT), polarizing microscope (PM), nuclear magnetic resonance imaging (NMR), and acoustic emission (AE) to reveal the mechanisms of physico-mechanical property deterioration [9]. Additionally, in most existing studies, researchers often combine SEM, thermogravimetric analysis (TGA), and differential scanning calorimetry (DSC) with X-ray diffraction (XRD) pattern analysis to examine the microstructural properties of rock minerals [5]. For example, [PERSON], [PERSON] [14] investigated the heat influence on the microstructure of limestone using XRD, SEM, TGA, and DSC tests.