Influence and mechanism of printing materials on the mechanical properties of sand powder 3D printed weak rock-like materials

The weak rock mechanics is the basis of the control of coal mine roadway surrounding rock, which is generally of low strength and fractured. Due to the special characteristics of weak rocks in mechanics and structure, etc., there are problems in physical experiments such as the difficulty of specimens to meet the characteristics of fractures in the field and the strong discrete nature, which seriously restrict the research of weak rock mechanics or fractured rock mechanics tests. 3D printing technology is widely used in rock mechanics test research because of its technical advantages such as digital modeling and high accuracy, which breaks through the limitation of casting method in making complex specimens with fractures, but the specimens printed and formed by this technology are influenced by the printing materials and parameters which needs to be studied in depth. Based on sand powder 3D printing technology, this paper investigates the behavior and mechanisms of the effects of different types of sand powders and different binder saturation on the mechanical properties of weak rock-like specimens by means of mechanical tests, acoustic emission monitoring and electron microscopy scanning. The results show that different types of sand powders have significant effects on the mechanical properties and damage modes of the formed specimens due to their particle shape, size, and arrangement; the binder saturation has a positive correlation with the strength of the specimens, and changing the binder saturation can increase the strength of the specimens by 5 times under the same sand powder type, while the acoustic emission event signal and energy also increase with the increase of binder saturation. The results help to reveal the applicability and optimization basis of sand powder 3D printing technology for physical simulation of weak rocks, and provide an important basis for accurate and scientific reduction of mechanical properties of weak rocks in specific engineering conditions.