Method of fabricating artificial rock specimens based on extrusion free forming (EFF) 3D printing

Three-dimensional (3D) printing technology has been widely used to create artificial rock samples in rock mechanics. While 3D printing can create complex fractures, the material still lacks sufficient similarity to natural rock. Extrusion free forming (EFF) is a 3D printing technique that uses clay as the printing material and cures the specimens through high-temperature sintering. In this study, we attempted to use the EFF technology to fabricate artificial rock specimens. The results show the physico-mechanical properties of the specimens are significantly affected by the sintering temperature, while the nozzle diameter and layer thickness also have a certain impact. The specimens are primarily composed of SiO2, with mineral compositions similar to that of natural rocks. The density, uniaxial compressive strength (UCS), elastic modulus, and tensile strength of the printed specimens fall in the range of 1.65–2.54 g/cm3, 16.46–50.49 MPa, 2.17–13.35 GPa, and 0.82–17.18 MPa, respectively. It is capable of simulating different types of rocks, especially mudstone, sandstone, limestone, and gneiss. However, the simulation of hard rocks with UCS exceeding 50 MPa still requires validation.