Abstract: The distribution of soil and epikarst zones in karst areas is highly heterogeneous. Depicting the characteristics of rocksoil structures is crucial for regional hydrological research and key zone model construction. Taking typical limestone slopes in central Guizhou as an example, this study uses high-density electrical method as the main exploration means. Geotechnical structures are characterized based on electrical resistivity tomography (ERT), , and combined with soil probing method and typical profiles for comparative verification, the rock-soil structures of limestone slopes are analyzed under complex geological conditions. The results show that the resistivity of the soil layer ranges from 0 to 89.4 Ω·m; the average resistivity values of karst fractures are less than 585.3 Ω·m for thick-layer limestone and less than 292.8 Ω·m for thin-layer limestone; The performance of the high-density electrical method is better for interpreting soil area than for karst fracture area in, and better under single structure conditions than under complex structure conditions, and the interpreted lithological boundary l is clear; the average soil thickness of the entire limestone slope is about 0.495 m, and the average thickness of the epikarst zone is about 3.921 m; the soil and karst fractures show high spatial heterogeneity, and the epikarst zone is discontinuous. The results can help further apply the high-density electrical method to detect and characterize the rock-soil structures under complex lithological conditions in karst areas, providing data support for constructing models for karst critical zones. 

Key words: ERT, rock-soil structure, epikarst, soil thickness, limestone slope