<p>Fault zones, which are common geological structures, are characterized by a “hard–soft–hard” structure. To simulate both “soft” and “hard” rock masses, versatile similar materials with tuneable properties were developed for application under true three-dimensional (3D) geostress conditions. Using iron ore powder, barite powder, quartz sand, rosin, alcohol, and white cement as raw materials, similar materials for rock masses with evident “soft” or “hard” characteristics were formulated through orthogonal design. The density, uniaxial compressive strength, elastic modulus, Poisson’s ratio, cohesion, and internal friction angle of the similar materials were measured through laboratory tests. The sensitivity of the factors was assessed via range analysis, and the effect of white cement was further analysed. Finally, the developed similar materials were successfully applied to a geomechanical model test on the tunnel response under true 3D geostress and fault dislocation. The results show that the similar materials have a wide range of physical and mechanical parameters, and can meet the requirements of different kinds of rock masses. The mass ratio of aggregates has the greatest influence on the material density, whereas the mass concentration of rosin has the greatest impact on the uniaxial compressive strength, elastic modulus, cohesion, and internal friction angle. White cement has a significant enhancement effect, and it can increase the mechanical properties of the similar materials and improve their brittleness and hardness. After fault dislocation, the rupture of the surrounding rock in the hanging wall is more severe, resulting in the lining suffering more severe failure. The observable failure range of the lining is located on both sides of the fault zone, and does not exceed 1.5 times the width of the fault zone. The materials can provide material support for obtaining good test results and can serve as a reference for the selection of similar materials for rock masses in similar model tests.</p>