Mechanical properties and failure characterization of rock splitting under high velocity impacts

In order to explore the mechanical properties and failure mechanism of sandstone under different impact loads, the dynamic splitting test of sandstone under different impact loads is carried out by using the separated SHPB test system. The stress-strain curve of sandstone is analyzed, and the basic mechanical properties of sandstone are expounded. Combined with the digital image correlation method （DIC）, the evolution of the intermediate main strain field is determined, and the failure mode of sandstone is explored. The broken rock blocks are classified and the degree of fragmentation of sandstone after tensile failure is analyzed. The research shows that the dynamic stress-strain curve of sandstone is divided into elastic deformation stage, plastic stage and failure stage. The failure mode of sandstone is that the stress concentration zone is formed at the initial stress, and the specimen is penetrated along the direction of stress wave, and the tensile failure occurs as a whole. The primary crack always participates in the failure. As the load increases, the role of the primary crack in the failure is aggravated, and the kinetic energy of the sample is also increased, so that the strain energy accumulated inside the sample is quickly released, resulting in more thorough development of the primary crack. The interconnection and continuous penetration of the new cracks are more significant, resulting in obvious shear failure. Based on fractal theory, with the increase of load, the crushing degree of sandstone is more intense. When the load increases further, the crushing degree of sandstone gradually tends to be stable. The research results provide a theoretical basis for studying the dynamic mechanical properties of rock and its application.