Thermal effects on failure characteristics of granite with pre-existing fissures

In order to study the effects of pre-existing fissures on the failure characteristics of granite after high-temperature treatment, granite samples containing three different sets of fissures were heated at different temperatures (100-800 degrees C), and then a uniaxial compression test was carried out. The major findings are as follows. (a) Temperature and pre-existing fissures have a great influence on the strength of granite. When the temperature is low, the compressive strength exhibits an approximately linear upward relation with increasing alpha in the range from 30 to 60 degrees. However, with increasing temperature, the effect of pre-existing fissures on the strength of granite decreases, and this trend of growth gradually diminishes. In addition, the thickness of granite samples (from 16 to 29 mm) has little effect on the strength of granite in this study. (b) The failure of granite is transformed from brittle to plastic deformation with elevated treatment temperature. In addition, according to failure patterns of granite, there are four crack failure modes under uniaxial pressure. Failure modes I and II occur below 600 degrees C, and failure modes III and IV mainly occur above 600 degrees C.