Effects of specimen size and thermal-damage on physical and mechanical behavior of a fine-grained marble

Both thermal damage and specimen size have a significant influence on the rock strength and deformation behavior. This study experimentally investigates the combined influences of thermal damage and specimen size on the strength and deformation behavior of a fine-grained marble. Uniaxial compression tests on specimens with different specimen sizes (diameters of 25, 50, 75, and 100 mm) and different treatment temperatures (25, 200, 400, and 600 °C) are conducted. After thermal treatment, the measured P-wave velocity is found to decrease and the amount of micro-cracks generated inside the specimen shows a drastic increase, indicating an increase in the thermally-induced micro-crack damage. The uniaxial compressive strength (UCS) is found to decrease with the increase in the treatment temperature and decrease as the specimen diameter gradually increases. The Young's modulus also gradually decreases with the increase in the treatment temperature. The peak strain corresponding to the peak strength gradually increases with the increase in the treatment temperature and shows a decreasing trend as the specimen diameter increases. The maximum volumetric strain is also found to show an increasing trend as the applied temperature increases. Rock specimens generally fail in a brittle splitting manner. The integrity of specimens after failure with higher temperature treatment will be lower than those with lower temperature treatment. By using a temperature dependent parameter, a new model which considers the combined effects of specimen diameter and treatment temperature is proposed.