| Landslide is an unexpected and catastrophic geological disaster. Rainfall is the main triggering factor for landslides. Natural slopes appear to be very uneven distribution of particle size because of various stresses, pore fluids, physical and chemical changes. The properties of slope soil vary spatially. Internal erosion and transport of fine particles may be induced by the seepage and infiltration of rainwater into a slope. The studies on the soil erosion mechanism and the influence of the internal erosion on the slope stability caused by rainwater infiltration have certain theoretical meaning and engineering value.With the infinite slope as research object, the influence of the internal erosion on the infiltration and slope stability is studied in this paper, using the numerical analysis method, based on the hydrodynamics of porous media and theories of unsaturated soil mechanics. The main research contents and results are as follows.1. In this study, a slope stability model considering coupling of seepage and internal erosion is established. The governing equation for transport of fine particles is coupled with the governing equation of transient seepage analysis for unsaturated soils, considering the unsaturated soil hydraulic characteristic equations, the relationship between the rate of eroded fine particles and the hydraulic gradient and pedotransfer functions.2. The homogeneous infinite slope finite element model is established to investigate the influence of the internal erosion on the infiltration and slope stability. The effects of the initial saturated permeability and air-entry value parameter on the slope stability and seepage are studied. The results of an illustrative example show that the internal erosion occurs mainly in the zone within the wetting front, which accelerates the advance of the wetting front and the slope stability is reduced consequently. The initial saturated permeability and air-entry value parameter are the main factors to affect the internal erosion in the slope. When the saturated coefficient of permeability is greater, the effect of the internal erosion on the infiltration and slope stability becomes more significant as long as the rainfall flux is equal or greater than the saturated coefficient of permeability. When the air-entry value of the soil is greater, the influence of the internal erosion on the infiltration and slope stability becomes less significant.3.Numerical simulations of internal erosion in four unsaturated soil slopes with different fine particles contents are conducted. Introduced the pedotransfer functions based on the unsaturated soil hydraulic characteristic parameters, the influence of the internal erosion on the infiltration and slope stability is studied considering the dynamic change of particle composition. The study shows that when fine particles content is less than 30%, the effect of the internal erosion on the infiltration and slope stability becomes more significant. when fine particles content is greater than 30%, the effect of the internal erosion becomes less significant.4.In this study, spatial random soils are investigated based on the random field theory. The spatial variability of soil properties is simulated using the covariance matrix decomposition method. Numerical simulation of internal erosion in heterogeneous soil slope is conducted to study the effect of heterogeneity on the internal erosion development process and the local and global stability.5.To investigate the initiation and development of internal erosion under rainwater infiltration, a laboratory testing of internal erosion to soil specimen is conducted. The testing results show that the relationship between the seepage velocity and accumulation of eroded fine particle is nonlinear. With the increase of flow velocity, fine particles continue to flow out, but the outflow decreases gradually. The cumulative loss of fine particles quality is increased, but the increase rate decreases. |
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