Development and Characterisation of Novel Fluid–Solid Coupled Similar Materials Under Dry–Wet Cycling Conditions

This study aims to develop fluid–solid coupled similar materials to enhance the reliability of geotechnical model tests simulating reservoir slope stability under water-level fluctuations. Using an orthogonal experimental method, materials were prepared with quartz sand and barite as aggregates, cement and gypsum as binders, and water as the regulator. Tests on density, uniaxial and triaxial compressive strength, and flow properties determined the relationships between material properties and raw components. Uniaxial compressive strength tests under dry–wet cycles revealed that cement-to-binder ratio primarily influenced density, uniaxial compressive strength, cohesion, and hydraulic conductivity, while the binder-to-aggregate ratio affected elastic modulus and internal friction angle. Uniaxial compressive strength continuously degraded with cycles but at a decreasing rate. A water-damage resistance coefficient was defined to quantify degradation. Multiple linear regression analysis established a robust model for uniaxial compressive strength prediction, providing a theoretical basis for material proportioning. These findings improve the simulation accuracy in hydrologically active zones, with applications in designing stable reservoir slopes.