Characteristics of Shallow Moisture Changes in Unsaturated Soil Slopes Covered with Vegetation under Different Rainfall Rates

Rainwater infiltration will significantly increase the pore water pressure of shallow soil, thus reducing the stability of slope soil. In order to study the migration law of rainwater infiltration wetting front of vegetated slopes, the law of rainfall infiltration was analyzed by using the data of in field monitoring test of slopes. Meanwhile, a vegetated slope infiltration model was established, and the changes in the pore pressure and saturation of the idealized root system on the slope under different rainfall were investigated and analyzed. We found that medium to heavy rainfall (>10 mm/d) can change the shallow water content of vegetated slopes, and light rainfall cannot change the water content; the change in water content of vegetated slopes is less than that of unvegetated slopes under long-duration rainfall, and more than that of unvegetated slopes under short duration rainfall; the change in water content of Ligustrum quihoui Carr. L. shrub slopes are smaller than that of Nerium oleander L. shrub slopes, which has a better effect of slope; under short duration rainfall, the permeability coefficient of root consolidation zone of the vegetated slope is large, the rainwater infiltration speed is fast and it is not easy to cause shallow landslides; with the increase of rainfall time, the plant root system provides a good pore channel, the depth of sudden change of pore pressure of vegetated slope is smaller than that of unvegetated slope. The results of this study provide a reference and analytical basis for vegetated slopes of road graben under rainfall.