Study on Dynamic Compressive Mechanical Properties and Failure Modes of Heat-Treated Granite

摘要

Temperature and external load are two important factors affecting the mechanical properties of rock material. The test on heat- treated granite specimen was carried out by using an improved split Hopkinson pressure bar (SHPB). Based on the test data, the dynamic behavior and failure characteristics of the granite under the coupling action of temperature and impact loading are studied. The results show that the amplitude of incident wave increases with the impact velocity of striker, and the shapes of the transmitted and reflected waves are closely related to the failure state of the specimen. The stress-strain curves for the heat-treated specimens above 700 o C are obviously different to those below 500 o C in terms of the slopes for the ascending segment and the peak stress, indicating that there is a temperature threshold between 500 o C and 700 o C. Under the same velocity, the strain rate decreases slightly and then increases as the temperature increases. At a constant temperature, strain rate increases linearly with the impact velocity. The relationship between elastic modulus and strain rate for the heat-treated specimen obviously tends to have no regularity. In addition, both peak stress and peak strain exhibit strain rate sensitivity, but different increasing rates for different temperatures are detected. Below 500 o C, the influence of temperature on peak stress and peak strain is not evident, however, the influence becomes remarkable at 700 o C and 900 o C.