The Impact of Dynamic Acid Rain Dissolution on Sandstone Pore Structure and Heat Transfer Characteristics

Acid rain-induced dynamic dissolution severely threatens the preservation of near-surface sandstone grottoes and carvings. This study experimentally investigates the temporal evolution of sandstone pore structure, thermal properties, and surface strength under such conditions. Results indicate a two-stage dissolution process: the initial stage shows higher porosity growth and pore volume ratio changes, primarily increasing pore number and size; the later stage significantly alters pore structure and connectivity. With prolonged dissolution, heating/cooling rates decrease, while thermal conductivity and specific heat capacity drop exponentially. Hardness and P-wave velocity also decline exponentially over time. Among the parameters analyzed, porosity exhibits the highest sensitivity to dissolution, followed by hardness and thermal conductivity. Strong correlations exist: hardness decreases linearly with porosity and increases nearly linearly with thermal conductivity, which itself declines exponentially with porosity. These findings enhance understanding of acid rain impacts on sandstone heritage and support the use of thermal infrared detection for assessing surface deterioration.