Numerical simulation of backward erosion piping in heterogeneous fields

Abstract

Backward erosion piping (BEP) is one of the major causes of seepage failures in levees. Seepage fields dictate the BEP behaviors and are influenced by the heterogeneity of soil properties. To investigate the effects of the heterogeneity on the seepage failures, we develop a numerical algorithm and conduct simulations to study BEP progressions in geologic media with spatially stochastic parameters. Specifically, the void ratio e, the hydraulic conductivity k, and the ratio of the particle contents r of the media are represented as the stochastic variables. They are characterized by means and variances, the spatial correlation structures, and the cross correlation between variables. Results of the simulations reveal that the heterogeneity accelerates the development of preferential flow paths, which profoundly increase the likelihood of seepage failures. To account for unknown heterogeneity, we define the probability of the seepage instability (PI) to evaluate the failure potential of a given site. Using Monte‐Carlo simulation (MCS), we demonstrate that the PI value is significantly influenced by the mean and the variance of ln k and its spatial correlation scales. But the other parameters, such as means and variances of e and r, and their cross correlation, have minor impacts. Based on PI analyses, we introduce a risk rating system to classify the field into different regions according to risk levels. This rating system is useful for seepage failures prevention and assists decision making when BEP occurs.

Recent Advances in Stability and Failure Mechanisms of Landslide Dams

“…The critical hydraulic gradient and the progression of internal erosion could be obtained by capturing the main hydraulic characteristics of the turbulent flow that occur in an erodible pipe and the seepage flow in the remaining area of a dam foundation (Wang et al, 2014;Rotunno et al, 2019). The heterogeneity could accelerate the development of preferential flow paths and increase the likelihood of seepage failures by verifying the stochastic parameters of the dam material, such as the hydraulic conductivity, void ratio, and grain contents (Liang et al, 2017). A local critical gradient rather than an average critical gradient FIGURE 12 | Failure patterns of a landslide dam for different materials: (A) sliding failure for a fine-grained landslide dam (Wang et al, 2018;Zhu et al, 2019); (B) no failure for a coarse-grained landslide dam; (C) erosion failure for a well-graded landslide dam (Xiong et al, 2018); (D) piping failure for a gap-graded landslide dam (Quenta et al, 2007;Xiong et al, 2018).…”

Computer modeling of water cleaning in wetland taking into account of suffosion ang colmatation

“…In terms of the physics of a phenomenon, study of the processes of migration of insoluble particles in saturated porous media can be considered from two sides. The first is the problem of suffusion [9] (in the simplest case -carrying away movable particles from the skeleton of a porous medium [10]), related to problems of safety for hydro-technical, civil and industrial facilities [11]. Along with suffusion, the problems of colmatation are considered [12].…”

Modeling suffusion of ideally gap‐graded soil

“…According to the experimental findings, the shear stress‐based method, which considers both hydraulic shear stress $${\tau _a}$$ and erosion coefficient $$\omega $$, was adopted in order to establish a continuum‐based numerical model. In general, for the soil model representing the erosion behavior in previous research, an additional fraction, representing the erodible particles, was required 12,13 . Subsequently, the erosion rate, $$\dot \varepsilon $$, and the initiation of erosion, which affect the concentration of erodible particles, were governed together by the general form as a function of hydraulic shear stress $${\tau _a}$$, as shown in Equation (1).…”