Salt weathering sensitivity assessment of surrounding rocks at the Kizil Grottoes

Salt weathering threatens the surrounding rocks of grottoes in arid regions. Previous studies have often considered salt load, pore structure, and clay-related moisture sensitivity separately, limiting interpretation of coupled deterioration. Here, mudstone, sandstone, and argillaceous fine sandstone from the Kizil Grottoes were analyzed by XRD, ion chromatography, and MIP. Whole-rock equivalent montmorillonite content (M′), total soluble salt content (TSS), and the Salt Susceptibility Index (SSI) were integrated into an M′–TSS–SSI ternary diagnostic framework. The framework distinguishes salt-load-sensitive, pore-structure-sensitive, clay-moisture-sensitive, and coupled types. These results indicate that similar deterioration can arise from different controls. The framework provides a comparative basis for sensitivity grading and targeted conservation.