Abstract: Under the combined effect of rainfall and water level fluctuation, the slope of the reservoir bank is prone to collapse. Ideal elastic-plastic Mohr-Coulomb criterion is used to analyze the stability of reservoir slope, which is difficult to characterize the complex mechanical characteristics of slope soils, such as over consolidation dissipation under wet-dry cycles. It is difficult to analyze the stability of bank slopes under the action of dry and wet cycles to reflect the complex mechanical properties such as overconsolidation and dissipation of slope soils. In this study, focusing on weakly overconsolidated unsaturated red clay at the reservoir bank slope of the Xingan shipping-hydropower junction project in Jiangxi Province, unsaturated direct shear tests were conducted and an overconsolidated unified hardening (UH) model for red clay was constructed. The UH model incorporates the mathematical-physical relationship between suction stress and matric suction using the arctangent function. Subsequently, based on the UH model, an application program of FLAC3D was developed in C++. The SEEP/W module of GeoStudio software was employed to compute the unsaturated seepage field during the rainfall infiltration, and an interface program was created to import FLAC3D data for stability calculations of the reservoir slope. Comparisons between the horizontal displacements obtained from the improved UH model and the classical unsaturated elastic-plastic model revealed significantly larger displacements in the former, suggesting that the improved UH model can provide reasonable predictions of the overconsolidated unsaturated red clay for reservoir slope stability. This research offers valuable insights for similar projects involving analyses of reservoir bank slope.

Key words: red clay, unified model (UH) model, suction stress, over consolidation, slope stability analysis