A grading method for analyzing internal erosion processes of nano-silica improved sand

Internal erosion can induce significant changes in the mechanical properties of soils, posing various hazards to dam and dike structures. Despite its importance, our current understanding of this phenomenon remains incomplete. The influence of pre-shearing stress conditions on the mechanical behaviours of soils during the internal erosion process is particularly challenging, as existing experiments have not been able to maintain the constant pre-shearing stress ratios. To bridge this gap in knowledge, this paper presents a series of discrete element method (DEM) simulations focused on gap-graded cohesionless soil. The primary objective of these simulations is to investigate two specific cases of internal erosion: suffusion and suffosion processes. Soil specimens are subjected to different pre-shearing stress ratios in the standard triaxial tests before being submitted to different levels of erosion to study their constitutive responses. The results show that erosion-induced deformation (i.e. suffosion) only starts after a specific amount of mass loss. This mass loss and the pre-shearing stress ratio form a well-defined criterion for triggering suffosion, which is named “suffosion surface”. The volumetric strain is shown to be a better indicator to describe the suffosion process than the commonly used void ratio. The pre-shearing stress ratio significantly influences the suffosion response of the soil sample, with a higher pre-shearing stress ratio facilitating soil failure. Furthermore, soil specimens undergo both deviatoric and volumetric responses during the suffosion process. To this end, new DEM-based statistical equations were proposed to describe the observed mechanisms, which are helpful for the future development of constitutive models to describe internal soil erosion.

Internal erosion often occurs in earthen water-retaining structures such as embankment dams, levees, and dikes. This erosion is caused by seepage flows through soils or other porous materials containing a mixture of coarse and fine particles. The internal erosion process, also known as suffusion, involves the transport of fine particles carried away from the soil structure by seepage. Internal erosion can weaken the soil, create voids or cavities, and ultimately lead to structural collapse, posing a significant risk to earthen water-retaining structures. This research investigates the internal erosion behavior of gap-graded sands with various fine fraction contents through a series of upward seepage tests. Using an in-house-developed apparatus to measure hydraulic gradient and permeability, this study examines the initiation and progression of internal erosion in detail. Additionally, it explores the effects of vertical stress and relative density on erosion behavior, as well as methods to control or mitigate erosion by incorporating different cement contents as an improvement measure for internal erosion control. Results indicate that internal erosion begins at a critical hydraulic gradient, with the migration of fine particles intensifying as the gradient increases. Vertical stress and relative density significantly influence erosion behavior, with higher stress and density improving resistance to erosion. Cement stabilization effectively mitigated erosion by reducing fine particle loss and enhancing soil stability. These findings contribute to a deeper understanding of seepage-induced internal erosion and support the development of strategies to improve the resilience of earthen structures.

HighlightsThis study provides data from internal erosion tests on four intermediate-scale homogeneous embankment dams.Soil properties influence the breach formation process and breach timing.Results showed that observed erosion rates of the internal flow path varied by several orders of magnitude.Quality control of embankment construction can greatly influence breach development.Abstract. Internal erosion and embankment overtopping are the two most common causes of embankment dam and levee failures and incidents. Internal erosion is the removal of soil material by the flow of water through a continuous defect, cavity, or crack within a compacted fill and/or its foundation. Internal erosion initiates from vulnerabilities within the embankment. The embankment soil material plays a key role in both the erosion process and rate of failure, but characterizing soil properties and how they relate to the rate of failure can be challenging. Soil properties such as texture, density, strength, moisture content, and erodibility can vary greatly; thus, it is important to study the effects of these properties on the breach formation process and breach timing. The USDA Agricultural Research Service performed internal erosion breach experiments on four intermediate-scale homogeneous earthen embankments constructed of soils ranging from a silty sand to a lean clay material. The embankments were constructed to a height of 1.3 m, a top width of 1.8 m, and upstream and downstream slopes of 3(H):1(V). The embankment materials were characterized by water content, density, texture, strength, and erodibility. Erodibility was measured using a jet erosion test (JET) apparatus. A 40 mm diameter, continuous steel pipe was placed through each embankment during construction and removed to form an open-ended void through the embankment connected to the upstream reservoir. The removal of the pipe initiated internal erosion. The objectives of the experiments were to observe the development of the internal erosion process over time and to examine the influence of soil properties on the erosion rate, breach timing, geometry of the breach opening, and breach outflow. The rate of erosion and failure observed in these tests varied by several orders of magnitude, with the silty sand embankment eroding most rapidly and the lean clay embankment with a mean moisture content of 18% dry basis at standard compaction eroding the slowest. These observations were indicative of the soil textures. Although the two lean clay embankments were constructed of similar soils, the difference in erosion rates speak to the importance of quality control (e.g., compaction moisture content) during construction. Soil properties including soil texture, erodibility, and compaction moisture content are key predictors of erosion rate and observed failure. Keywords: Breach, Dam failure, Dams, Embankments, Erodibility, Internal erosion, Levees, Overtopping.

The process of internal erosion in an embankment dam with granular filters can be divided in five stages : (i) formation of the crack through the core, (ii) erosion of material from the crack walls due to the shear stress applied by flowing water, (iii) transport of eroded particles to the filter, (iv) retention or percolation of these particles within the filter, (v) continuation of erosion leading to piping failure, or sealing of the crack. The process is quite well known in case of non-cohesive base soils, but if the base is a clayey soil, the process is much more complex. Based on a large number of No Erosion Filter tests performed at the University of Granada, (Spain), this paper analyses the influence that have several base soil's variables in the internal erodability of clayey soils protected by granular filters, such as plasticity, mineralogy, water content, additives and hydraulic gradient.

Two embankment dams form part of a series of reservoirs built at the turn of the nineteenth century to supply water locks that are used to ascend and descend over the summit of the Rochdale canal. The embankments are homogeneous with no engineered waterproof barrier and consist mainly of weathered clayey sandstone fill over peat/glacial till over bedrock. There is a history of instability during the early part of the dams' life, with buttress berms added. There have not been any recent incidents at either of the reservoirs and recent monitoring data suggest that there are no embankment stability issues and internal erosion processes are not currently manifested. Nevertheless, homogenous embankment dams are inherently vulnerable to internal erosion. Extensive risk analysis has been undertaken at both dams, which has provided the basis for identifying failure mechanisms that are estimated to have an individual risk that is within the Health and Safety Executive (HSE) ‘intolerable’ range (i.e. individual risk when conservatively estimated as the probability of failure is greater than 10−4 per annum). This paper describes the risk analysis used to evaluate potential remedial measures to reduce the risk to a tolerable limit using the ‘as low as reasonably practicable’ principle as recommended in HSE guidelines.

Seepage-induced internal erosion occurs when the hydraulic forces are sufficient to detach fine particles and transport them out of the structure, leading to notable changes in soil characteristics such as particle size distribution, pore size distribution, and pore structure, which will, in turn, have significant influences on the mechanical properties of soil. In this study, three approaches were utilized to model the erosion-induced loss of fine particles, i.e., deleting fine particles randomly (RM), by contact force (CF), and by coordination number (CN) using the discrete element method (DEM). The impact of each fine particle removal mode on both micro- and macro-mechanical soil properties, including peak strength, dilation, critical state characteristics, average particle coordination number, and contact force distribution, is comprehensively analyzed and compared. The results demonstrate that residual strength was insensitive to removal method, whereas at 10% fines loss, peak strength decreased by up to 17% and the secant stiffness E50 decreased by nearly 48%. This work provides a foundation for simulating the internal erosion of gap-graded soils.

Internal erosion is one of the most common causes of failure in hydraulic engineering structures, such as embankments and levees. It also plays a vital role in the geohazards (such as landslides and sinkhole developments) and more importantly, the earth landscape evolution, which has a broad environmental and ecosystem impacts. The groundwater seepage is multi‐directional, and its multi‐dimensional nature could affect the initiation and the progression of internal erosion. With a newly developed apparatus, we carry out nine internal erosion experiments under five different seepage directions. The results reveal that the critical hydraulic gradient increases as the seepage direction varies from the horizontal to the vertical. After a global erosion is triggered, preferential erosion paths distribute randomly from the bottom to the top of the specimen. If the seepage direction is not vertical, small preferential erosion paths merge into a large erosion corridor, in which the loss of fine particles is significant but negligible outside. Results of experiments manifest that the erosion is heterogeneous and three‐dimensional, even in the unidirectional seepage flow. The particles are rapidly eroded at the early stage of the erosion, indicating a high erosion rate. With the erosion time increasing, the particle loss slows down and even ceases if the time is long enough. The erosion rate increases if the seepage direction approaches a vertical direction. Overall, the erosion rate approximately decreases with erosion time exponentially. We proposed exponential equations to illustrate the variation of the erosion rate in the erosion process.

Removal of fine particles in wet flue gas desulfurization system by heterogeneous condensation

Dams are essential elements in infrastructure and country’s development. It are historically constructed to store water, however, today dams are built for various purposes, such as irrigation, energy availability, water supply, waste retention, and flood control. All the dams in the world show some degree of leakage, occurring through the foundation, in the contact with the natural terrain or through the dam. One of the main causes of dam rupture is the process of internal erosion caused by leaks. Tracers can be used to understand the water flow in the dam to perform corrective activities to reduce risks. The objective of the study was to research the state of the art of tracers techniques applied to water leakage in dams. We used 78 references, such articles, publications and books, using as inclusion criterion all the materials with the theme involving dams and tracers applied to it. This article reviews these techniques and shows their importance in the early detection of leaks, to realize correct interventions to ensure the stability of the structure, avoiding disasters with incalculable damage to populations and the environment.

Coupled CFD–DEM Investigation of Erosion Accompanied by Clogging Mechanism under Different Hydraulic Gradients

A017 USING RESISTIVITY MEASUREMENTS FOR DAM SAFETY EVALUATION AT ENEMOSSEN TAILINGS DAM 1 SJODAHL P.* DAHLIN T.* JOHANSSON S.** * Dept. of Engineering Geology Lund University Box 118 221 00 Lund Sweden pontus.sjodahl@tg.lth.se torleif.dahlin@tg.lth.se ** HydroResearch Sam Johansson AB St. Askens vag 6 183 65 Taby Sweden sam.johansson@hydroresearch.se INTRODUCTION Internal erosion is one of the major reasons for embankment dam failures. Resistivity measurements may have the possibility of detecting internal erosion processes and anomalous seepage at an early stage before the safety of the dam is at stake. The technique is essentially non-destructive which is particularly important when working with

The detection of internal erosion is critical in monitoring and developing risk assessments for dikes and levees. This paper presents a geophysical approach that is both sensitive to the internal erosion process and can be implemented on large scale. It is therefore considered to be a major asset for monitoring and developing risk assessments for dikes and levees. With the exception of temperature and hydro-acoustic measurements, self-potential (a passive electrical technique) is the only geophysical method which is sensitive to a fluid flow in a porous media. The SCAN Leak approach outlined in this paper is based on acquiring multiple arrays of self-potential measurements using overwater data acquisition, which allows 2 to 4 kilometers per day of dikes and levees to be surveyed. The system has been commercially used on several projects and has been demonstrated to fulfill the criteria for the detection of internal erosion within dikes and levees. The SCAN Leak approach uses multi-channel data acquisition to record self-potential variations. From a single pass alongside the dike / levee, a plan map of the self-potential variations can be plotted, allowing the detection of anomalous features, both parallel and perpendicular to the survey direction. This paper presents the findings of a survey conducted in the south-east of France along a concrete-lined canal that was known to have significant outflow or leakage. The surveyed covered a swath of the canal several kilometers long and approximately 10 meters in width. Our investigations have shown that self-potential anomalies can arise through electro-redox phenomena from canal infrastructure such as pipework. Strong spatial correlation between discrete structures within canals and SP anomalies has allowed validation of the sensitivity of a the self-potential acquisition system (SCAN Leak) that can also detect electro-kinetic sources (water inflow and outflow). In this case study, using the SCAN Leak system, we show how SP anomalies are associated with electro-kinetic processes taking place at a known downstream outflow location. This multi-channel waterborn SP system offers a rapid investigation / screening tool for the assessment of internal erosion with dikes and levees.

Promoting the removal of fine particles and zero discharge of desulfurization wastewater by spray-turbulent agglomeration

Landslide dams, typically composed of newly deposited, loose, and heterogeneous materials, are highly susceptible to failure induced by overtopping and seepage, particularly under extreme hydrological conditions. Accurate prediction of such breaching processes is essential for flood risk management and emergency response, yet existing models generally consider only a single failure mechanism. This study develops a mathematical model to simulate landslide dam breaching under the coupled action of overtopping and seepage erosion. The model integrates surface erosion and internal erosion processes within a unified framework and employs a stable time-stepping numerical scheme. Application to three real-world landslide dam cases demonstrates that the model successfully reproduces key breaching characteristics across overtopping-only, seepage-only, and coupled erosion scenarios. The simulated breach hydrographs, reservoir water levels, and breach geometries show good agreement with field observations, with peak outflow and breach timing predicted with errors generally within approximately 5%. Sensitivity analysis further indicates that the model is robust to geometric uncertainties, as variations in breach outcomes remain smaller than the imposed parameter perturbations. These results confirm that explicitly accounting for the coupled interaction between overtopping and seepage significantly improves the representation of complex breaching processes. The proposed model therefore provides a reliable computational tool for analyzing landslide dam failures and supports more accurate hazard assessment under multi-mechanism erosion conditions.

Internal and external pipeline erosion due to suspended particulate matter, wax and sand content, and geoseismic motion can rapidly reduce pipeline wall thicknesses to critically low values. Due to low shrinkage rates on curing, epoxy polymer coatings are well suited for slowing the rate at which pipe wall thickness is lost. The abrasion resistance of an epoxy coating is a function of the hardness of the coating, the abrasive particle velocity, angle of impact, and particle size. This paper describes the authors’ attempts to estimate longevity of certain Bisphenol-A based epoxy coatings against particulate abrasion. Details are presented for the abrasion resistance testing of four different commercial epoxy coatings. Experimental methodology is detailed consisting of two different methods of accelerated erosion testing: water-jet droplet erosion and fixed frequency mechanical abrasion. The methods are used to calculate abrasion endurance lifetime for a variety of pipeline installation environments. Test samples are exposed to abrasive wear for a given period of time and material loss is measured. Loaded and unloaded abrasion testing is used to represent forces proportional to buried and non-buried piping. Erosion volume and time to the specified erosion depth are compared with control data on uncoated carbon steel substrates. This accelerated erosion data is transposed to reflect in-situ life expectancies.