PRELIMINARY STUDY ON UNIAXIAL MECHANICAL CHARACTERISTICS OF BRITTLE COAL WITH 3D PRINTING MATERIALS

Traditional rock sampling methods and mold casting are often affected by manual operation errors and complex internal structure differences. They can result in long cycle time and low accuracy of rock specimen acquisition, as well as large discrete mechanical test results of samples. 3D printing technology has the advantages of high precision, short period and diversified printing materials. The past rock mechanics research is affected by factors including anisotropy of specimen, complex structural plane, high randomness and specimen preparation error. We seek 3D printing materials that can simulate coal and rock with different hardness. We select the plastic poly(lactic acid)(PLA), photosensitive resin material SLA600 and Vero White Plus, four kinds of materials and coated sand powder materials. We prepared standard mechanical test specimens in uniaxial compression test, obtain the mechanical parameters of four kinds of materials and the stress strain curve, and analyze the four kinds of materials and fracture mode of the coal and rock. The results show the follows. At the peak strength, Young's modulus, Poisson's ratio and stress-strain curves of the photosensitive resin Vero White Plus are similar to those of the floor sandstone. The peak strength, Young's modulus and stress-strain curves of the coated sand are similar to those of the coal samples. In terms of apparent failure mode, PLA material has no similar brittle failure to coal rock. Tensile and shear fracture occurred in both photosensitive resins. SLA600 exhibits local expansibility. Vero White Plus is better suited to simulate brittle hard rock with high strength than SLA600. The fracture characteristics and mechanical properties of the coated sand 3D printing specimen are similar to those of low-strength soft rock, which can be used as 3D printing similar material of low-strength brittle coal.