Stability evaluation of artificial dam structures in abandoned mine underground reservoirs under non-uniform biaxial loading conditions

• 2D beam model developed for dam stability in underground reservoirs. • Analytical method estimates shear force, moment, and deflection. • Cement dam specimens tested under non-uniform biaxial loading. • Experimental and numerical results quantify lateral pressure effects. • Theory aligns with test data to identify instability threshold. With the rapid growth of abandoned mines resulting from carbon neutrality and industrial restructuring efforts, repurposing these subsurface spaces for underground energy storage has become a promising and sustainable approach. This study focuses on the stability of artificial dam structures used in underground reservoirs within abandoned mines, which are crucial for ensuring operational safety under complex stress conditions. A two-dimensional beam model with uniform cross-section and fixed boundaries was developed to simulate the dam's mechanical response under non-uniform biaxial loading induced by overburden and lateral water pressure. Segmented analytical expressions for shear force, bending moment, and deflection were derived. Laboratory tests, conducted using a self-developed non-uniform biaxial loading apparatus, and DEM-based numerical simulations revealed that increasing lateral pressure areas led to a transition in failure modes from splitting to shear, forming a distinctive inverted "V-shaped" fracture, which was confirmed both experimentally and numerically. Theoretical calculations showed strong agreement with experimental measurements of lateral strain and deformation trends, validating the proposed analytical model. The results provide a solid theoretical and experimental foundation for optimizing dam design, clarifying failure mechanisms, and enhancing structural reliability in underground energy storage systems constructed within legacy mine spaces.