The physical and mechanical parameters and degradation mechanisms of red sandstone in the Mount Wuyi scenic area were studied under the action of dry–wet cycles. Dry–wet cycle, acoustic wave velocity, water saturation rate, and triaxial compression tests were conducted, aided by scanning electron microscopy and X-ray diffraction testing techniques. The study’s results show that the dry–wet cycle effect on red sandstone is a major factor in the degradation of its physical and mechanical parameters and that its microstructural characteristics are significantly affected. The P-wave velocity, peak strength, elastic modulus, internal friction angle, and cohesion decreased, the water content and peak strain increased, and the elastic modulus was the most sensitive to dry–wet cycles. A dry–wet cycle’s action severely damages the microstructural integrity of the red sandstone. After 15 dry–wet cycles, the interstitial fillings between the skeletal grains are dissolved over a large area, microfractures are interwoven throughout, and the structure is severely fragmented. The microstructural degradation of the red sandstone by dry–wet cycles mainly manifests in the dissolution of the interstitial filler, and the relative content of calcite as an interstitial filler is reduced by 46.6% after 15 dry–wet cycles. The proposed strength decay prediction equation has reference significance for the strength prediction of the red sand conglomerate in the project. This study’s results can provide theoretical support for the landscape protection of rock masses and the prevention of engineering geological hazards.

The safety of rock landscapes in Mount Wuyi is significantly impacted by acid rain and wet-dry cycles. In this paper, the decay characteristics of the physical–mechanical properties of red glutenite were investigated under acidic wet-dry cycles. A systematic approach, including cold field emission scanning electron microscopy (CFE-SEM), image processing techniques, and X-ray diffraction (XRD), was proposed to investigate the damage mechanism of red glutenite under acidic wet-dry cycles. The results indicate that with increasing solution acidity and wet-dry cycles, dry density (DD), longitudinal wave velocity (LWV), uniaxial compressive strength (UCS), and elastic modulus (EM) of red glutenite significantly decrease. Under different acidic conditions, DD, LWV, and UCS exhibit exponential decay with wet-dry cycles, while EM exhibits linear decay. A regression fitting was employed to establish a prediction model for UCS, which exhibited a better capability in predicting the correlation between UCS, pH, and the number of wet-dry cycles. Microscopic comprehensive analysis reveals that the interaction between rock dissolution and desiccation is the primary factor leading to changes in the microstructure and mineral composition of red glutenite, culminating in the decay of its physical–mechanical properties. This study holds significant guidance implications for the preservation of cultural and natural heritage in Mount Wuyi.