Computer simulations and physical modelling of erosion

Proceedings of the 7th International Conference on Scour and Erosion, Perth, Australia, 2-4 December 2014, 2014

From observations of experiments, breach widening processes in levees are described as undermining of side slopes. Due to the erosion and detachment of soil under water level, an overhanging developed and soil mass above losses their stability to fail down. Cracks along the surface are observed at the initiation of soil mass failure and then opened along the main one until the soil mass topples into the breach opening. These above processes will continue until hydraulic forces of discharge flow are too small to erode more soil. In this study, a toppling failure model of levee side slope recession is proposed. It takes into account the evolution of eroded notch, the scale of levee and the tensile strength of soil. Comparison of the simulated results obtained by SLOPE/W showed that this toppling failure model can well assess the magnitude of levee side slope recession with simple parameters inputted.

Climatic changes are expected to increase both the frequency and severity of flooding across the world. It is not possible to plan a continuous increase of levee height and its geometry. Therefore levees should resist to overtopping. This Technical Note gives an updated review of the surface erosion phenomena that can occur during floods and mainly deals with a case history on the effect of overtopping on a trial embankment in stabilized soil. The possible use of recycled soil is also discussed.

The two most significant parameters which affect the erodibility of soils are soil plasticity and soil compaction during the levee construction. The erodibility potential of levee material has an influence on scour generation due to overtopping from floodwalls. In this investigation, 1/20 scaled physical models with different soil plasticity indexes and compaction levels are considered to evaluate levee performance against scouring. Typical levee construction methods for Mississippi river levees were followed for construction of physical models. In each test, the soil mass was compacted in several thin layers to reach the targeted field compaction. During the lab tests, different geometric and hydraulic parameters of levee and flow were monitored to identify the scour development. The Froude number of the flow was measured in each test to ensure a reasonable comparison between the flow in laboratory-scaled test and typical overtopping in the field. The results of physical modeling tests indicate how the scour potential for levees vary with different soil plasticity and compaction levels during the construction.

IAEME PUBLICATION, 2019

Many dam ruptures events have occurred throughout the world, Then main cause was piping phenomenon that occurred in the foundation soil or in the dam structure. Serviceability of hydraulic infrastructures needs considering vulnerability of soil to internal erosion under the action of a seepage flow. Understanding the underlying mechanisms and quantifying the effects of pertinent variables that affect this phenomenon is of great importance in order to prevent such catastrophes. Erosion due to liquid flow discharge can be modeled by different. In this work, the water erosion is modeled in the water/soil interface during the hole erosion test (HET). The Hole Erosion Test is commonly used to quantify the rate of piping erosion. The aim of this work is to predict the erosion of soil in the water/soil interface by using the Fluent package and three dimensional modeling .This modelling makes it possible describing the effect of the flow on erosion in the interface water/soil by using the k − turbulence model equations, and predicts a non uniform erosion along the hole length unlike the usual one dimensional models. In particular, the flow velocity is found to increase noticeably the erosion rate Effects on the wall-shear stress resulting from varying flow velocity and applied hydraulic gradient are analyzed.

Water resources engineering, 1995

Wittler and B. W. ~efford', S.R Abt and J.F. R&, G. W. ~n n a n d a l e ~ PG&E, EPRI, Reclamation, Colorado State University, and HDR Engineering are collaborating on improving technology for estimating the progressive extents of dam foundation erosion due to overtopping. This paper compares erosion prediction methods, and explains the basis for the development of new technology. The primary objective of the investigation is to develop a scheme for estimating the progressive extents of erosion for cohesive and noncohesive materials as well as hctured rock masses. The investigation involves researching existing methods and data, conducting a systematic series of physical model tests, and developing a numerical model for simulating the progressive extents of erosion. A numerical model with properly formulated boundary conditions, simulating physical processes rather than parametric empirical correlation, will provide a useful tool for estimating progressive extents of dam foundation erosion. Mason and Anunugam (2) list 31 methods of calculating scour depth, and divide these into five groups. The first group, 17 equations, relates scour depth to discharge, head drop and characteristic particle size. The second group, 2 equations, adds the impact of tailwater depth. The third group, three equations, is empirical in nature, and relates estimated scour depth to jet dimensions and characteristics. The fourth group, eight equations, developed by six Russian authors, relate scour depth to drop height, particle diameter, tailwater depth and the angle with which the falling stream enters the downstream area. The fifth group, one equation, is for equations that include a time parameter. Mason (3) also treats the impact of air entrainment on plunge pool scour. The equations and associated coefficients of Mason and Arumugam (2) and Mason (3) are state of the art. Veronese (4) and Mason (2) developed the most prominent scour equations. Equation 1 is the Veronese equation. Reclamation includes the Veronese equation in Design of Small Dams (1).

Proceedings of Advances in …, 2010

Recent research studies revealed that most bridge piers and other hydraulic structures such as levees and embankments adopted in flood protection schemes in maritime environment have collapsed due to the failures attributed to scour associated with a soil-hydrodynamic interaction phenomenon (e.g. Shirole and Holt, 1991). Though erosion characteristics of coarse sands and gravels are relatively well known, soil-hydrodynamics interaction for finer sands such as silts and clays is not fully investigated. A series of small-scale laboratory experiments were conducted in a moveable sediment tank to investigate scour characteristics under various flow and soil conditions. The present paper discusses preliminary experimental observations and the analysis of hydrodynamic erosion of soils in line with the extensive research project "Mathematical and Physical Modelling of Hydrodynamic Erosion of Soils (HES)" carried out under the "UEL Promising Researcher Fellowship 2009-2010" funded by the University of East London (UEL).

Allowing a concrete dam to overtop during extreme flood events is an alternative to spillway augmentation. Designing for dam overtopping requires an analysis of the erosion potential of the dam foundatinn m-d ab?~Lxents. C n~e~t fcm-das fcr evdgatifig ercsiox ,'lave Emit& app!iab%ty. Existing formulas do not track erosion as a function of time, and have limited application in hardrock or cohesive foundation materials.

Coastal Engineering Proceedings, 2014

A levee erosion model is developed to predict the temporal and cross-shore variations of vertical erosion depth under irregular wave action. The product of the erosion rate and the turf resistance force is related to the wave energy dissipation rates due to wave breaking and bottom friction. The turf resistance force is expressed using the turf thickness and the surface and underneath resistance parameters. The empirical parameters are calibrated using available data. The calibrated model has been shown to reproduce the relation between the limiting velocity and steady flow duration, the erosion rate on a seaward grassed slope, and the eroded profile evolution of a seaward clay slope. The levee erosion model is also compared with field tests for erosion on the landward slope caused by wave overtopping. It is found to be difficult to reproduce the observed erosion initiation and progression because of the wide variations of the grass cover and clay resistance. The turf resistance parameters will need to be calibrated for specific levees.

Science and practice for an uncertain future, 2021

Predicting breach erosion processes is essential for the effective risk management of both dams and levees. In recent years, a variety of research efforts have improved our knowledge of erosion processes, and in particular validation of the work on headcut erosion through cohesive soils performed at USDA-HERU. A similar level of analysis and validation is required for coarser grained and mixed materials to provide a clearer overview of when breach erosion processes change from headcut through surface erosion to slumping of rockfill. Since the release of flood water through a breached dam or levee depends both upon the rate of soil particle erosion and the macro erosion process (i.e. whether headcut or surface erosion or some other process occurs) it is important to ensure that conditions for these macro and micro erosion processes are understood in relation to different soil types and conditions, and that any breach prediction models correctly reflect these processes. This paper pre...

Lecture Notes in Civil Engineering, 2019

Lecture Notes in Civil Engineering (LNCE) publishes the latest developments in Civil Engineering -quickly, informally and in top quality. Though original research reported in proceedings and post-proceedings represents the core of LNCE, edited volumes of exceptionally high quality and interest may also be considered for publication. Volumes published in LNCE embrace all aspects and subfields of, as well as new challenges in, Civil Engineering.