Dynamic mechanical behaviors of sand-powder 3D printing rock-like specimens under coupled static and dynamic loads

The surrounding rocks of deep coal mine roadway are weak and fractured, and some dynamic disasters are easily induced by external dynamic loads. Therefore, dynamic test with soft rock and jointed rock mass is an important basis to solve the above problems. The 3 D printing technology can overcome the limitations of the casting method in making complex joint rock-like specimens, thus it is widely used in experimental research in the field of rock mechanics, and the key to its application is the similarity between the 3 D printing specimens and natural rocks in static and dynamic mechanical properties. With sand-powder 3 D printing specimens, the similarity of elastic-plastic properties between the sand-powder 3 D printing and coal specimens was revealed by carrying out conventional mechanical tests, such as uniaxial compression and Brazilian tests. The split Hopkinson pressure bar(SHPB)device was used to carry out different coupled static and dynamic loads tests. The dynamic response and failure characteristics of specimens were studied by means of macroscopic fragmentation and mesoscopic scanning electron microscope. The results show that the dynamic strength and combined strength are positively correlated with the increase of impact pressure, and the dynamic strength is negatively correlated with the increase of axial pressure. The combined strength increases first and then decreases with the increase of the axial pressure, which shows that the dynamic-resistant ability of the specimens increases first and then decreases with the increase of axial pressure. With the increase of static and dynamic loads, the fragmentation of the specimens is gradually fine-grained, and the dynamic load has the most notable influence on the fragmentation of the specimen. This paper reveals the dynamic characteristics of the sand-powder 3 D printing specimens and verifies the feasibility of its application in the dynamic tests with coal and soft rocks, and hereby provides an important basis for rock dynamics tests using the sand-powder 3 D printing technology. The research results contribute to further investigations on the dynamic failure characteristics of surrounding rock under different in-situ stress and dynamic load conditions.