Evolutionary characteristics of mode-I fracture toughness and fracture energy in granite from different burial depths under high-temperature effect

Abstract

For urgent solutions to existing major engineering problems such as deep mining and deep burial of high level radioactive nuclear wastes, exploring the mechanical behaviors of rocks under the synergistic effect of the burial depth of rocks and temperature is of great significance. The mode-I fracture characteristics of granite specimens in the semi-circular bending (SCB) test under the effects of different temperatures and burial depths were experimental investigated. The test results showed that the mineral compositions and fracture characteristics of granite both varied significantly at different burial depths in Daliuhang Gold Mine in Yantai, Shandong Province, China. The high-temperature effect would remarkably weaken the influence of the burial depth on the fracture characteristics of granite; moreover, increasingly growing temperature gradually became a dominant factor influencing the fracture characteristics of granite. As the temperature rose from 20 °C to 900 °C, the peak strength, fracture toughness and fracture energy of granite at different burial depths all declined with the temperature rise. Additionally, a significant quadratic polynomial function relationship was found in temperature with peak strength and fracture toughness. Additionally, it was macroscopically found that the fracture energy linearly increased with the fracture toughness, implying that the specimens with larger fracture toughness need to consume more energy during the failure. However, the specific proportions and rates of energy consumption differed in different fracture stages of granite.