Dynamic impact mechanical properties of red sandstone based on digital image correlation method

In the process of underground blasting excavation, the safety and stability of rock mass are significantly influenced by dynamic load. To study the full-field strain and displacement behaviour of rock materials subjected to dynamic compressive force, the impact tests were done on red sandstone specimens using an electromagnetically driven Hopkinson pressure bar. At the same time, the data were collected by a high-speed camera, and non-contact measurements of the red sandstone were carried out with the digital image correlation method. The resulting images were screened and analysed, based on which the stress-strain curve, full-field strain cloud diagram and displacement cloud diagram were obtained. Results show that the dynamic peak stress increases with the increase of impact velocity. During the impact process, substantial internal uneven deformation occurs in the red sandstone close to the transmission bar's end face. Under the impact load, the cracks initiate from the upper and lower sides near the transmission bar's end face, followed by formation of cracks in the middle part. These cracks expand throughout the rock to form through-cracks, eventually resulting in complete failure. For rock materials, the evolution of their strain field during the failure process can reflect the initiation and propagation of their internal cracks. Therefore, the use of digital image correlation method proves effective for studying the deformation and failure mechanisms of rock. The conclusions obtained in this study provide a valuable reference for the macro-meso deformation and failure mechanisms of geotechnical materials.