Abstract: To explore rock strength characteristics and fracture mechanisms under different cooling methods, limestone subjected to high temperature was naturally cooled or water-cooled. Brazilian splitting tests and acoustic emission measurements were performed on the limestone samples after high-temperature treatment, tensile strength under different cooling methods was measured, and the tensile and shear crack evolution during failure was analyzed using a K-Means algorithm. A numerical model of limestone was constructed by using PFC, and the influence of temperature and cooling mode on the tensile strength, crack evolution, displacement field and force chain of limestone was analyzed. The results show that: (1) The tensile strength of limestone decreases with the increase of temperature, and the strength of limestone cooled by water is lower than that under natural cooling conditions. Compared with the limestone without high temperature treatment, the tensile strength of naturally cooled limestone at 200−600°C decreases by 21.8%, 62.8% and 77.3%, and the tensile strength of limestone cooled by water decreases by 54.5%, 65.3% and 79.2%. (2) As temperature increases, pre-peak acoustic emission events increase and internal damage accumulates; tensile cracks are observed throughout loading, while shear cracks occur mainly near the peak and post-peak stages. (3) With increasing temperature, crack complexity increases; under water cooling, the main crack arises from numerous cracks, event magnitudes become more frequent, the displacement field becomes more irregular, and the stability of force-chain networks decreases.

Key words: limestone, cooled by water, acoustic emission, fracture pattern, PFC