| In the course of service, concrete cutoff walls in earth-rock dams are often affected by seepage dissolution, which can lead to structural performance degradation, failure of the anti-seepage system, and seepage-related damage to the dam foundation. This study presents a new coupled seepage-dissolution model for analyzing the performance deterioration of the anti-seepage walls in earth-rock dams. The model is developed based on the theories of saturated-unsaturated seepage and conventional calcium leaching, taking into account the effect of seepage on the non-equilibrium dissolution of solid-phase calcium within the concrete. The model's validity is verified through laboratory seepage-dissolution tests. The long-term seepage-dissolution evolution characteristics of the anti-seepage walls in a specific earth-rock dam project are investigated. The performance evolution of the anti-seepage walls during the seepage-dissolution process is analyzed, revealing the degradation patterns. A new criterion based on the critical hydraulic gradient is proposed to estimate the safe service life of the concrete cutoff wall. The results show that calcium leaching from the anti-seepage wall mainly occurs at the upstream water-facing surface, at the locations of seepage bypasses, and at the interface between adjacent soil layers. During the seepage-dissolution process, the leaching of solid-phase calcium, the average porosity, the diffusion coefficient, and the permeability coefficient all increase exponentially over time, leading to a gradual weakening of impermeability. Throughout the dam's service life, the coupled effects of seepage and dissolution result in an increasing hydraulic gradient within the anti-seepage wall. The critical hydraulic gradient-based method provides a reliable estimate of the safe service life of the concrete cutoff wall. For a completely dissolved concrete cutoff wall, the porosity increases by approximately sevenfold, while the permeability and diffusion coefficients increase by about 2-3 orders of magnitude. |