Assessing shallow slope stability using electrical conductivity data and soil hydraulic characteristics

In-situ slope monitoring techniques can be used to observe hydrological and mechanical processes in soil, identify the development of unstable slope areas, and provide information for slope stability models. In recent years, the combination of hydrogeological surveys and geophysical monitoring methods has enabled us to obtain the geotechnical and hydrological propertied associated with landslides. However, the highly heterogeneous subsurface settings make it challenging to correlate geophysical monitoring data with soil engineering properties. In this study, we investigated the relationship between soil water content and electrical conductivity, and then associated it with the soil water characteristic curve and suction stress characteristic curve obtained by laboratory tests to derive the soil water potential–electrical conductivity curve and suction stress–electrical conductivity curve. Then, we extended the shear strength model for unsaturated soils to correlate the shear strength model with the matric suction and electrical conductivity. To verify the model rationality, we adopted the finite element analysis model HYDRUS-2D and Slope Cube Module to solve the variably saturated flow and stress problems and used the obtained local safety factor to evaluate the slope stability. The shear strength model developed in this study was applied to estimate the changes in shear strength at the study site, and the results were compared with in-situ displacement observations. We found that the shear strength model can indicate shallow slope failures caused by increased soil water content. The slope stability analysis revealed that the variation trend of the local safety factor is consistent with that of the shear strength, indicating that the shear strength model established in this study with electrical conductivity as a variable can reasonably evaluate slope stability, and is also suitable for analysis related to the hydraulic properties of unsaturated soils.