Moisture change law and slope stability analysis of expansive soil ecological slope under rainfall

Rainfall infiltration is one of the important factors in topsoil slip of expansive soil slopes. In order to study the migration law of wetting front under rainfall infiltration on ecological protection slope, the spatiotemporal response law of soil moisture content of slope was analyzed by using the real-time data collected by in-situ monitoring of engineering slope. At the same time, the physical and mechanical parameters of the root-soil composite were determined by laboratory tests. The fluid-structure interaction model under rainfall infiltration on the prototype ecological protective expansive soil slope was calculated by finite element software, focusing on the analysis of the trend of sliding surface position and safety factor of the ecological slope after rainfall. Finally, the time-variant data of soil saturation at the monitoring point location in the model slope was compared with the real-time monitoring data of the same location, and then the soil reinforcement depth of the ecological slope of oleander was comprehensively determined. The results of the study show that the rainfall that can cause changes in the volumetric moisture content of the three types of slopes is moderate to heavy rain (10～＜50 mm/d). The light rain (＜10 mm/d) cannot cause changes in the shallow moisture content of the slope. The variation of water content of ecological slope under long-term rainfall condition is smaller than that of vegetation slope, while the variation of short-time rainfall (≤24 h) is larger than that of vegetation slope. The variation of water content of ligustrum quihoui carr slope is smaller than that of oleander slope, and the slope protection effect is better. The safety coefficient of the ecological slope is greater than that of the plain soil slope under the actual rainfall conditions, which indicates that the plant root system has an improvement effect on the slope stability. The dynamic variation of saturation of the model slope matches with the monitoring data, and the dense-branched depth of the root system represented by the root depth of 0.2 m can represent the soil reinforcement depth of oleander root system in the simulation. The conclusion of this study can provide a reference and analysis basis for the study of ecological control measures of expansive soil cut slope under rainfall conditions. © 2023, Central South University Press. All rights reserved.