A 3D printing method for granite-like materials with customized mechanical properties for deep rock physical modeling

Purpose This study aims to develop a 3D printing method for fabricating granite-like materials with customized mechanical properties to support accurate physical modeling of deep rock masses. The method integrates material design, printability control and mechanical similarity evaluation. Design/methodology/approach Natural granite from a deep tunnel was selected as the prototype, and its mineral composition and mechanical properties were used to guide the formulation of granite-like materials. Thirteen mix proportions were designed using a uniform design method, considering aggregate gradation, cementitious content and barite powder dosage. To ensure compatibility with wet-material extrusion, the effects of sodium gluconate and hydroxypropyl methylcellulose on setting behavior, flowability and extrudability were systematically evaluated. Granite-like specimens were fabricated using a self-developed extrusion-based 3D printing system and assessed through microscopic observations and mechanical loading tests. Findings The printed granite-like specimens exhibited dense and homogeneous particle packing without interlayer defects. The optimal mix proportion successfully replicated the stress–strain response, failure mode and key mechanical indices of natural granite. Based on the similarity constant of uniaxial compressive strength, the similarity deviations for tensile strength, elastic modulus and brittleness index were 12.3%, 9.2% and 14%, respectively. These results confirm the feasibility of achieving customized mechanical properties through controlled composition and printability adjustments. Originality/value The proposed method provides a reliable pathway for producing 3D-printed rock analogues with high similarity to natural rocks, enabling high-fidelity simulation of deep rock.