Overtopping Erosion Research Articles

Multiscale Investigations of Overtopping Erosion in Reinforced Tailings Dam Induced by Mud-Water Mixture Overflow

The overtopping failure that occurred to the reinforced tailings dam has led to devastating catastrophes, including severe environmental disasters as well as tragedy in terms of any loss of properties and life. To study the feature of overtopping erosion for the reinforced fine-grained tailings dam induced by mud-water mixture overflow, the red mud concentration of overflow, the erosion depths and erosion rate have been consistently detected and recorded by a series of physical model tests. This investigation conclusively showed that the red mud concentration for flooding over the dam slope had a nonlinear trend of first becoming larger, subsequently decreasing with the time going on in the process of tailing dam overtopping; the maximum red mud concentration achieved 19.0%. The erosion on the dam slope was shaped like a trumpet. The red mud concentration of the mud-water mixture flow affected the erosion depth significantly. The hydraulic tests simulating erosion behaviour in the reinforced fine-grained tailings were carried out with different red mud concentrations (0%, 10%, and 20%). For the mud-water mixture flow in a red mud concentration of 20%, the final erosion depth exhibited a ladder shape from the front to the trailing end (dam toe) of the tailings sample. The final erosion depths were 1.56 cm, 0.9 cm, and 0.55 cm at the front, middle, and trailing end, respectively. With the red mud concentration decreasing, the final erosion depth at the front of the tailings sample reduced significantly while increasing at the trailing end. This study brought more scientific insights into the overtopping erosion process to the reinforced fine-grained tailings dam triggered by the mud-water mixture flow at multiscale.

WinDAM C: Analysis Tool for Predicting Breach Erosion Processes of Embankment Dams Due to Overtopping or Internal Erosion

HighlightsThe computational models comprising the current version of WinDAM, called WinDAM C, are summarized.WinDAM C estimates the response of an earthen embankment subjected to overtopping or internal erosion.WinDAM C is a model that quantifies erosion/breach processes observed in physical embankment failure tests.Understanding the current technology and limitations provides a basis for further model development.Abstract. Internal erosion and overtopping erosion of earthen embankments are the leading causes for earthen embankment failures. Challenges like reservoir sedimentation, structural deterioration, rodent damage or tree root growth, and changing hazard classification from low to significant or high have arisen with aging dams. To address these challenges, new technology and tools for predicting the performance of homogeneous, cohesive earthen embankments during overtopping or internal erosion are needed. Windows Dam Analysis Modules (WinDAM) is a modular software application developed through collaborative efforts of the United States Department of Agriculture (USDA) Agricultural Research Service (ARS), the USDA-Natural Resources Conservation Service (NRCS), and Kansas State University (KSU) in response to this need. WinDAM uses a simple storage routing model to simulate flow through a reservoir and incorporates algorithms for predicting the progression of erosion resulting from embankment overtopping or flow through an internal discontinuity in the embankment. These algorithms are based on existing literature and data and observations from physical model experiments of homogeneous, cohesive embankments conducted by scientists at the USDA-ARS Hydraulic Engineering Research Unit in Stillwater, Oklahoma. The resulting computational model is a simplified representation of the observed process of progressive erosion that may lead to embankment breach. This paper reviews the components of the erosion/breach process and the way in which these components are quantified and integrated into the current WinDAM software, WinDAM C. The scope of application of the software, limitations, and computational assumptions are also discussed. Keywords: Breach, Dams, Erodibility, Erosion Process, Failure, Internal erosion, Model, Overtopping, Piping.

Overtopping erosion of model earthen dams analysed using digital image-processing method

Overtopping erosion is one of the main factors responsible for the destruction of earthen structures due to floods. Considering the shortage of existing studies and the need for further research to properly understand the processes leading to breaching failure, this study investigates the effect of compaction level (dry density) on the overtopping erosion response of model compacted silty sand dams using a laboratory flume apparatus. From side-view video recordings of the homogeneous earthen dam cross-section, digital image-processing techniques are employed to track and forensically analyse and interpret the initiation and progression of the erosion edge. The results indicate that the overall pattern of initiation and development of overtopping erosion depends on the compaction level, with greater compactive effort (higher shear strength of soil) reducing its progression speed, thereby increasing the time period for the erosion edge to reach the dam's upstream crest (tB) and breaching failure. Artificial neural network and response surface methodology (RSM) approaches are investigated for estimating the experimental tB values, with the RSM-derived third-order polynomial found to produce good predictions for the three compaction levels investigated. Finally, recommendations are given for further research, including employing the experimental set-up presented for investigating other types of dam failure.

Overtopping Failure of a Reinforced Tailings Dam: Laboratory Investigation and Forecasting Model of Dam Failure

Overtopping failure of reinforced tailings dam may cause significant damage to the environment and even loss of life. In order to investigate the feature of overtopping of the reinforced tailings dam, which has rarely appeared in the literature, the displacement, the phreatic level and the internal stress of dam during overtopping were measured by a series of physical model tests. This study conclusively showed that, as the number of reinforcement layers increased, the anti-erosion capacity of tailings dam was notably improved. It could be supported by the change of the dimension of dam breach, the reduction of stress loss rate, and the rise of phreatic level from the tests. Based on the erosion principle, a mathematical model was proposed to predict the width of the tailings dam breach, considering the number of reinforcement layers. This research provided a framework for the exploration of the overtopping erosion of reinforced tailings dam, and all presented expressions could be applied to predict the development of breach during overtopping.

Numerical and experimental study on the formation mode of a landslide dam and its influence on dam breaching

The deposition morphology of a landslide dam determines the position of initial breach and sequentially affects the direction of lateral erosion. Twenty-seven discrete element numerical simulations were carried out to investigate the deposition morphology of landslide dams concerning three factors, which include the valley shape, the valley bed inclination and the landslide velocity. The simulation results show that the valley shape and the landslide velocity affect the dam morphology in both transverse and longitudinal directions, while the valley bed inclination mainly affects the longitudinal morphology of dams. Further, a flume experiment was carried out to investigate the specific effects of the dam morphology on the overtopping erosion of landslide dams. The results of experiment show that for the dams in different deposition morphologies and with different initial breaches, the breach widths and the total sediment discharges induced by overtopping erosion are different.

The classification of landslide dams based on duration time until overtopping erosion

The classification of landslide dams based on duration time until overtopping erosion

Debris Flow Simulation by Applying the Hyper KANAKO System for Water and Sediment Runoff from Overtopping Erosion of a Landslide Dam

Debris Flow Simulation by Applying the Hyper KANAKO System for Water and Sediment Runoff from Overtopping Erosion of a Landslide Dam

Combined wave and surge overtopping erosion failure model of HPTRM levees: Accounting for grass-mat strength

High performance turf reinforcement mat (HPTRM) has emerged as an effective and flexible strengthening system to protect earthen levees against the erosion caused by overtopping flows. The purpose of this study is to characterize the erosion and failure processes of HPTRM-strengthened levees under combined wave and surge overtopping. The Erosion Function Apparatus (EFA) is used to analyze the erodibility of HPTRM-strengthened clay. The erodibility parameters such as critical shear stress and erodibility coefficient are then obtained. A HPTRM-element model is proposed to account for the mechanism of HPTRM in protecting cohesive soil with the help of EFA results in the characterization of the grass mat strength parameter. At last, a failure model is developed based on the excess stress equation, and the durations of HPTRM-strengthened levees against combined overtopping with different wave heights and freeboards are presented.

Overtopping erosion and failure mechanism of earthen levee strengthened by vegetated HPTRM system

Prior studies have shown that the protection of landward-side slope of earthen levees against wave and surge overtopping during large storm surges is of great importance. In this research, a full scale flume test and erosion function apparatus tests were conducted to study the overtopping erosion and failure mechanism of landward-side slope of earthen levees strengthened by high performance turf reinforcement mat (HPTRM). An examination of soil loss from strengthened levee in the full-scale flume tests showed that overtopping flow velocity more correlated with soil erosion along the levee crest and landward-side slope than the shear stress. It is found that erosion starts near toe in the landward-side slope during combined wave and surge overtopping. The erodibilities of vegetated HPTRM system and grass were compared, and the result showed that the vegetated HPTRM system and grass increased the threshold on erosion. However, after the threshold velocity is reached, the vegetated HPTRM system performs much better on erosion resistance than the grass does. A conceptual model for soil loss from levee surface is presented to describe two erosion mechanisms of levee surface, erosion starting position and the roles of the key hydraulic parameters (flow velocity/shear stress).

Study on developing process of water channel by landslide dam overtopping erosion

Study on developing process of water channel by landslide dam overtopping erosion

Slope Stability Analysis of Earthen Levee Strengthened by High Performance Turf Reinforcement Mat under Hurricane Overtopping Flow Conditions

The slope stability of levees during hurricane overtopping conditions involving storm surge and wind generated wave action is an important aspect to assess the safety of earthen levees. A comprehensive slope stability investigation was conducted in this study for an earthen levee subjected to full-scale overtopping scenarios, including storm surge only overflow, wave only overtopping, and combined wave and surge overtopping conditions. The crest and the landside of the levee were strengthened by high performance turf reinforcement mat (HPTRM) to protect against overtopping erosion. A conceptual model for HPTRM strengthened levee as well as a methodology for analysis and incorporation of various overtopping flow conditions in levee slope stability is presented. The findings of this study indicate that HPTRM strengthening of the levee improves the stability of the levee significantly during wave only as well as combined storm surge and wave overtopping conditions. However, during the storm surge conditions, the factor of safety is only improved slightly as a result of strengthening of the levee by HPTRM.

Primary Study on Overtopping Erosion of Non-Viscous Embankment and Assessment of Discharge through Breach

Combined with the flume experiments and 1D unsteady flow numerical model, the paper has investigated the overtopping breach process of the non-viscous embankment. The breach expansion and the variation process of water level above the breach gate have been studied by series of experiments. Considering the difficulty to monitor the discharge through the breach, 1D unsteady flow numerical model has been applied to simulate discharge variation process. It is found that the width of breach gate and water level above the breach gate are the two key factors which influence the discharge through the breach significantly. Discharge variation process through the breach gate is consistent with the flow rule of side weir. The calibrated flow coefficient is from 0.389 to 0.696. The investigation results can provide scientific basis for disaster prevention and evaluation of embankment burst.

Numerical simulation of landslide dam overtopping erosion process considering side bank collapse

Numerical simulation of landslide dam overtopping erosion process considering side bank collapse

Levee Erosion by Overtopping in New Orleans during the Katrina Hurricane

Erodibility of a soil is defined here as the relationship between the erosion rate of a soil dz∕dt and the velocity v of the water flowing over it, or the relationship between the erosion rate of a soil dz∕dt and the shear stress developed by the water at the water-soil interface. This is called the erosion function. The test used to measure the erosion function of the levee soils is the erosion function apparatus test. The test consists of eroding a soil sample by pushing it out of a thin wall steel tube and recording the erosion rate for a given velocity of the water flowing over it. Several velocities are used and the erosion function is defined. A new erosion category chart is proposed to reduce the erodibility of a soil or rock to a single category number. Twenty three samples were retrieved from 11 locations at the surface of the levees around New Orleans. Thirteen were samples from Shelby tubes while ten were bag samples. The results obtained show a large variation of erosion resistance among the soils tested. Some of the levees associated with the location of the samples resisted the overtopping erosion very well; others eroded completely. On the basis of the erosion test results and of the observed behavior of the levees during the hurricane, a chart is presented which can be used to select soils for overtopping resistance. Numerical simulations were performed using the program CHEN 3D to obtain the distribution of velocity vectors in the overtopping flow and of shear stresses at the interface between the water and the levee surface. The comparison of the numerical simulation results and of the erosion function gives added credibility to the proposed levee overtopping erosion chart.