关键词: 岩石动力学, 高温作用, 动抗压强度, 动应变, 动弹性模量, 分离式Hopkinson压杆(SHPB)

Abstract: To investigate the effect of high temperature on physical and dynamic mechanical properties of limestone, basic physical tests were conducted on limestone specimens at room temperature and high temperature treatment from 100 ℃ to 800 ℃. Moreover, dynamic impact compression tests under the same loading conditions were also conducted using SHPB test device. Test results indicate that the main mineral composition of limestone is calcite and dolomite. At room temperature, the limestone has a compact structure. With the increase of treating temperature, the dolomite gradually decomposes into micro-sized particles, and the surface color of test specimens gradually changes from off-white to white. Moreover, the volume of test specimens increases, while its mass, density and P-wave velocity decrease. These variation rates are closely related to the temperature. Dynamic compression stress-strain curves of limestone specimens under different high temperatures are basically consistent. A small increase followed by a significant decrease can be observed for both the dynamic compressive strength and dynamic elastic modulus with the increase of the temperature. An obvious negative quadratic function relationship is also found between these dynamic parameters and the treating temperature, and the maximum value is observed at 200 ℃. However, parameters including the dynamic strain and strain rate of test specimens, and the treating temperature are in a positive quadratic function relationship. The failure modes of specimens transit from brittle to ductile brittle, and damage degree is the lowest at 200 ℃. The damage degree increases with the increase of temperature, and the size of limestone fragments gradually decreases, which basically becomes powder at 800 ℃.

Key words: rock dynamics, high temperature treatment, dynamic compressive strength, dynamic strain, dynamic elastic modulus, split Hopkinson pressure bar (SHPB)