Effect of rock loading rate based on crack extension and propagation.

When subjected to constant static load, after a period of damage accumulation and crack development, the rock will fail under a load lower than its compressive strength. The transform of loading rate may have a certain influence on the mechanical properties of rock. In order to investigate the effect of loading rate on mechanical properties of red sandstone, the propagation form of internal cracks in the subcritical propagation stage in rock under static loading is defined as tensile. Based on Maxwell model, the expression of effective tensile stress for crack extension in rock is deduced, which explains the phenomenon of rock tensile failure. Based on the uniaxial compression test of red sandstone under different loading rates, and the surface deformation field of specimens is analysed with the method of digital image correlation, and the corresponding relationship between the loading rate effect and the change of mechanical properties as well as the energy accumulation and release characteristics is analysed, the phenomenon of rock tensile failure is further verified. This research can be effectively applied to geotechnical engineering disaster warning.