A large number of earthen heritage sites are preserved in the alpine regions of northwestern China. Under the coupled action of freeze-thaw cycles and water-salt effects, the shallow surface layer of these sites undergoes repeated freezing and thawing, which induces various forms of deterioration. To investigate the deterioration characteristics of the near-surface layer of earthen heritage sites under the coupled action of freeze-thaw cycles and water-salt effects, laboratory freeze-thaw simulation tests were conducted. Based on six indicators-apparent morphology, surface temperature field, sonic wave velocity, surface hardness, microstructure, and particle size distribution of remolded samples-the deterioration characteristics of the shallow surface layer under the coupled influence of freeze-thaw cycles and salt migration were revealed. The experiments found that during freeze-thaw processes, soluble salts migrate towards the center of the samples and crystallize, thereby inducing salt weathering and forming a horizontal deterioration layer. Salt content shows a positive correlation with freeze-thaw damage, and higher Na₂SO₄ content leads to more severe damage. Freeze-thaw cycles significantly reduce sonic wave velocity and surface hardness, and disrupt the aggregated structure of soil particles, although the particle size gradation characteristics of the soil remain stable. The primary factor in the deterioration of the shallow surface layer of earthen sites is the coupled action of freeze-thaw cycles and water-salt effects, which causes salt accumulation and crystallization, damages the cementation state of soil particles, and leads to a loosened soil structure. The relevant findings can provide a reference for the prevention and mitigation of deterioration in the shallow surface layer of earthen heritage sites.

The long-term stability of stone cultural relics is a key concern in their preservation. This study focuses on the Bodhisattva statue in front of the reclining Buddha carved on Dazu Rock Carvings. Using bilateral filtering algorithm, the point cloud data from a 3D laser scanner were processed in the PCL platform to remove noise, preserving the surface details of the cultural relics. A refined 3D model of the Bodhisattva statue, including its fissure structure, was established. The statue’s stability was analyzed using the strength reduction method with FLAC3D software. The findings include: 1) The denoising method resultes in an average deviation of -5.0 mm to 4.0 mm and a standard value of 1.1 mm, which completely retained the artifact’s surface characteristics. 2) Under gravity load, the statue’s neck compressed while the top stretched, with cracks in the head redistributing internal stress, and the peak tensile stress moving from the top to the crack end. 3) The statue’s head displacement correlates positively with the reduction coefficient, sharply increasing at 1.28, indicating a tendency to tip. 4) The failure surface extends along the crack and neck into the relic’s interior, with the plastic zone and maximum shear strain increment forming a parabola through the two regions. This method offers insights for analyzing the stability of small stone artifacts with complex geometries.