Quantitative characterization of similarity in mechanical properties of postprocessed 3D sand-printed rock-like materials

• A postprocessing approach is used to improve the mechanical properties of 3DSP specimens. • The relationship between the postprocessing parameters and mechanical properties is investigated. • A quantitative method is proposed to evaluate the similarity between the 3DSP specimens and natural rocks. • Postprocessing and similarity quantification are validated by testing on preflawed specimens. 3D sand printing (3DSP) technique can be used to prepare rock physical models with complex structures. However, the printed specimens exhibit low strength and stiffness. To address this problem, a postprocessing method that combines vacuum infiltration of phenolic resin with heat curing is applied. A quantitative method is proposed to evaluate the similarity between 3DSP specimens and natural rocks. The influence of postprocessing parameters, including the vacuum-infiltration time and heat-curing temperature, on the mechanical properties is investigated via mechanical tests. The mechanical properties of the specimens exhibit an improvement trend with increasing vacuum-infiltration time, accompanied by a decrease in growth rates. Heat-curing temperature, however, demonstrated a critical threshold. Below this temperature, the mechanical properties are significantly enhanced, while exceeding it results in mechanical property degradation. Through similarity evaluation, the optimal postprocessing scheme for preparing sandstone analogs is determined as a vacuum infiltration time of 24 h and a heat curing temperature of 250°C. Validation tests involving specimens containing a flaw demonstrate that physical models produced by this scheme exhibit high consistency with sandstone containing a flaw in terms of stress‒strain curve, mechanical properties, and fracture behavior. These findings provide a reference basis for preparing and quantitatively evaluating rock-like specimens.