<p>The study aims to investigate the carbonated water erosion mechanism of lining concrete in tunnels traversing karst environment and enhance its resistance. In this study, dynamic carbonated water erosion was simulated to assess erosion depth, microstructure, phase migrations, and pore structure in various tunnel lining cement-based materials. Additionally, Ca²⁺ leaching was analyzed, and impact of Ca/Si molar ratio in hydration products on erosion resistance was discussed by thermodynamic calculations. The results indicate that carbonated water erosion caused rough and porous surface on specimens, with reduced portlandite and CaCO₃ content, increased porosity, and an enlargement of pore size. The thermodynamic calculations indicate that the erosion is spontaneous, driven by physical dissolution and chemical reactions dominated by Gibbs free energy. And the erosion reactions proceed more spontaneously and extensively when Ca/Si molar ratio in hydration products was higher. Therefore, cement-based materials with higher portlandite content exhibit weaker erosion resistance. Model-building concrete, with C-S-H gel and portlandite as primary hydration products, has greater erosion susceptibility than shotcrete with ettringite as main hydration product. Moreover, adding silicon-rich mineral admixtures can enhance the erosion resistance. This research offers theory and tech insights to boost cement-based material resistance against carbonated water erosion in karst tunnel engineering.</p>