Internal Erosion Research Articles

This study evaluates the retrofit design of the Semat weir on the Kali Gawe in Jepara Regency. The retrofit aims to adjust the weir’s hydraulic capacity to accommodate estimated flood discharges while ensuring the structure’s stability under applied loads. In the agricultural context, adequate water availability for irrigation directly affects crop yields; conversely, the rainy season often increases river flow and flood risk. Irrigation structures such as weirs are therefore required to raise river water levels to divert flow into irrigation channels and to regulate water distribution. Flood discharge estimates were derived from precipitation data and watershed (drainage basin) characteristics. Flood hydrograph planning is a critical design step for the weir. Log-Pearson Type III analysis was used to determine probable precipitation values for several recurrence intervals. Those design precipitation values were then converted into design flood discharges using synthetic unit hydrograph methods, specifically the Snyder, Nakayasu, and Gamma HSS approaches. Employing the Gamma synthetic unit hydrograph for the 50-year return period (Q50) produced a design flood discharge of 2,536.52 m³/s for that recurrence interval. Structural stability analyses of the redesigned weir indicate safety factors well above customary thresholds: overturning resistance factor = 11.6 (required ≥ 1.5), sliding resistance factor = 4.80 (required ≥ 2.0), and piping (internal erosion) factor = infinite (required ≥ 4). All evaluated stability parameters therefore satisfy standard safety criteria.

A fully-resolved micromechanical simulation of piping erosion during a suction bucket installation

Backward erosion piping in numerical models: A literature review

Internal erosion is a significant issue caused by water flow within soils, resulting in structural collapse of hydraulic structures, particularly in coarse soils located near rivers. These soils typically exhibit granulometric instability due to low clay content, resulting in poor hydraulic and mechanical properties. To mitigate this problem, cement treatment is applied as an alternative to soil removal, reducing transportation and storage costs. The hole erosion test (HET) and Crumbs tests, shearing behaviour through consolidated undrained (CU) triaxial, and microstructure analyses regarding scanning electron microscopy (SEM), mercury intrusion porosimeter (MIP) and thermogravimetric analysis (TGA) were conducted for untreated and treated coarse soil specimens with varying cement contents (1%, 2%, and 3%) and curing durations (1, 7, and 28 days). The findings indicate a reduction in the loss of eroded particles and overall stability of treated soils, along with an improvement in mechanical properties. SEM observations reveal the development of hydration gel after treatment, which enhances cohesion within the soil matrix, corroborated by TGA analyses. MIP reveals the formation of a new class of pores, accompanied by a reduction in dry density. This study demonstrates that low cement addition can transform locally unsuitable soils into durable construction materials, reducing environmental impact and supporting sustainable development.

ABSTRACTThis study relies on the high ablation resistance strategy of char layer expansion ceramization to strengthen the char layer and improve ablation performance. The use of phase change material, that is, paraffin wax, was effective in simultaneously improving the ablation resistance and thermal insulation performance of liquid methyl vinyl silicone rubber (LMVSR) composites, which was attributed to the low density, enhanced char layer, and improved heat‐absorption capacity. The introduction of paraffin wax lowered the ablation temperature and increased the specific heat capacity of LVMSR‐based composites, thereby enhancing heat dissipation and reducing thermal erosion. In addition, paraffin wax was able to promote the ceramization reaction. The mass erosion rate, pyrolysis rate, and graphitization degree of the char layer were significantly improved when the content of paraffin wax was increased from 5 to 15 phr. The composites with 15 phr paraffin wax demonstrated the best performance and the highest modification effect. The paraffin modification was effective in reducing the mass ablation rate, especially at 10 phr, which showed a decrease of 34.43% when compared with that of the L‐P0 counterpart. The maximum back‐face temperature was reduced by 29.63% upon adding 15 phr paraffin wax when compared with L‐P0, exhibiting excellent thermal insulation performance. The above results showed that the ablative resistance, internal erosion resistance, and thermal insulation properties of silicone rubber‐based composites were significantly improved by using the strategy of expansion ceramization and enhanced heat absorption/dissipation by adding phase change materials, which shows potential application in preparing flexible thermal ablative material for thermal protection purposes.

Abstract The study investigates the interaction between the grout curtain and bedrock foundation of the Nosice Dam, which is located in a geologically heterogeneous environment on the Váh river in Slovakia. By applying numerical modeling (the Finite Element Method) and analyzing water pressure test data, the research aims to assess the effectiveness of a grout curtain in controlling seepage. An extensive parametric study examines the impact of different rock permeability values on the reduction of seepage, which aids in the optimization of the depth of a grout curtain. This approach underscores the importance of advanced numerical modeling for dam safety and seepage control. The results could contribute to the knowledge of dam seepage control measures and could provide valuable insights about similar hydraulic structures. They could potentially mitigate risks, such as internal erosion and foundation instability associated with uncontrolled seepage.

A major hazard to embankment dams is internal erosion and piping arising from concentrated leaks through transverse cracks in the core near the crest due to differential settlement or desiccation. Erosion is controlled by the wall stresses resulting from flow in the crack, the critical shear stress, and rate of erosion properties of the soil. Many older embankment dams have filters or transition zones downstream of the core to arrest erosion, but the filter or transition is coarser than required to satisfy modern no-erosion filter design criteria, so erosion potentially initiates and progresses. We previously presented an analysis of flow through such transverse cracks without a filter, applicable to homogeneous embankments. This present analysis models flow in embankment cracks with a vertical filter downstream. Capillary and adhesion processes are neglected. Multiphase flow computations are avoided by assuming that the filter is saturated and then demonstrating that pressure along the separating streamline between the crack discharge and the saturated zone is ∼0. The consequent water levels and hydraulic shear stresses within the cracks are then determined. Plausible methods for adapting the assumed geometry and flow conditions to other commonly-occurring arrangements are also presented.

To accommodate the extreme thermodynamic effects and erosion damage in throttling equipment for ultra-high-pressure natural gas wells (175 MPa), a coupled multiphase flow erosion numerical model for nozzles was established. This model incorporates a real gas compressibility factor correction and is based on the renormalized k-ε RNG (Renormalization Group k-epsilon model, a turbulence model that simulates the effects of vortices and rotation in the mean flow by modifying turbulent viscosity) turbulence model and the Discrete Phase Model (DPM, a multiphase flow model based on the Eulerian–Lagrangian framework). The study revealed that the nozzle flow characteristics follow an equal-percentage nonlinear regulation pattern. Choked flow occurs at the throttling orifice throat due to supersonic velocity (Ma ≈ 3.5), resulting in a mass flow rate governed solely by the upstream total pressure. The Joule–Thomson effect induces a drastic temperature drop of 273 K. The outlet temperature drops below the critical temperature for methane hydrate phase transition, thereby presenting a substantial risk of hydrate formation and ice blockage in the downstream outlet segment. Erosion analysis indicates that particles accumulate in the 180° backside region of the cage sleeve under the influence of secondary flow. At a 30% opening, micro-jet impact causes the maximum erosion rate to surge to 3.47 kg/(m2·s), while a minimum erosion rate is observed at a 50% opening. Across all opening levels, the maximum erosion rate consistently concentrates on the oblique section of the plunger front. Results demonstrate that removing the front chamfer of the plunger effectively improves the internal erosion profile. These findings provide a theoretical basis for the reliability design and risk prevention of surface equipment in deep ultra-high-pressure gas wells.

ABSTRACTThe subsoils of river dikes are often composed of highly permeable and low‐density river sediments. Thus, erosion signatures (leaks, sand boils, sinkholes) can appear in the protected floodplain during floods, highlighting the development of hydromorphodynamic phenomena below the surface, which may harm the safety of the dike system. A multiscale methodology is deployed to understand and analyze the influence of floodplain architecture in terms of geological formations on the appearance of local erosion signatures. Particular attention is paid to the morphology of paleovalleys and paleochannels in order to image the subsurface in terms of substrate types and interfaces using geophysical methods. This information makes it possible to propose internal erosion scenarios. Application to a study area in the South of France (the Agly dike system) leads to new results. The classical backward erosion piping scheme is not relevant to explain the observed sand boils, as they are mainly caused by the suffusion‐type internal erosion process. Suffusion and contact erosion appear to be the origin of sinkholes. The distribution of these signatures appears to be directly related to the shape and dimensions of the paleovalley and paleochannels, as well as to the presence of a low‐permeability topsoil.

The internal erosion effect causes fine particles in the soil to move through seepage, and the loss of these fine particles leads to changes in porosity, which in turn affects the soil's hydraulic properties and mechanical performance, posing a threat to the safety of dam and levee engineering. To understand the formation and development of internal erosion under reverse seepage, a simulation test device for internal erosion was designed, and experiments were conducted on three granite residual soil samples with identical soil properties under different water flow speeds (25L/H, 50L/H, and 100L/H). By comparing and analyzing the wetting front, the amount of internal erosion, and the water content, the influence of water flow speed on reverse seepage internal erosion was studied. The results show that under reverse internal erosion, as the water flow speed increases, the internal erosion rate accelerates, as evidenced by the faster advancement of the wetting front and the increase in cumulative internal erosion. As internal erosion develops, the fine particle accumulation curve enters a stable phase. After the soil's water content reaches its peak, it slightly decreases and then remains relatively stable. Fluctuations in the soil water content occur due to the formation of preferential internal erosion channels or the redeposition of fine particles. The soil particle movement, fine particle loss, and redeposition caused by internal erosion create an internal erosion channel that narrows from the inlet to the outlet.

Numerical investigation of threshold effects in internal erosion of granular soils using coupled DEM-DFM

Numerical modelling of rainfall-induced internal erosion process within vegetated deposited slopes

Probabilistic investigation of the whole process of backward erosion piping for a two-layered levee in spatially variable soils

River embankments are critical flood defense structures, stretching for thousands of kilometers across alluvial plains. They often originated as natural levees resulting from overbank flows and were later enlarged using locally available soils yet rarely designed according to modern engineering standards. Substantially under-characterized, their performance to extreme events provides an invaluable opportunity to highlight their vulnerability and then to improve monitoring, management, and reinforcement strategies. In May 2023, two extreme meteorological events hit the Emilia-Romagna region in rapid succession, causing numerous breaches along river embankments and therefore widespread flooding of cities and territories. These were followed by two additional intense events in September and October 2024, marking an unprecedented frequency of extreme precipitation episodes in the history of the region. This study presents the methodology adopted to create a regional database of 66 major breaches and damages that occurred during May 2023 extensive floods. The database integrates multi-source information, including field surveys; remote sensing data; and eyewitness documentation collected before, during, and after the events. Preliminary interpretation enabled the identification of the most likely failure mechanisms—primarily external erosion, internal erosion, and slope instability—often acting in combination. The database, unprecedented in Italy and with few parallels worldwide, also supported a statistical analysis of breach widths in relation to failure mechanisms, crucial for improving flood hazard models, which often rely on generalized assumptions about breach development. By offering insights into the real-scale behavior of a regional river defense system, the dataset provides an important tool to support river embankments risk assessment and future resilience strategies.

Earth fill dams are susceptible to internal erosion and instability when founded over cavity-prone formations such as gypsum or karstic limestone. Subsurface voids can significantly compromise dam performance, particularly under seismic loading, by altering seepage paths, raising pore pressures, and inducing structural deformation. This study examines the influence of cavity presence, location, shape, and size on the behavior of zoned earth dams. A 1:25 scale physical model was tested on a uniaxial shake table under varying seismic intensities, and seepage behavior was observed under steady-state conditions. Numerical simulations using SEEP/W and QUAKE/W in GeoStudio complemented the experimental work. Results revealed that upstream and double-cavity configurations caused the greatest deformation, including crest displacements of up to 0.030 m and upstream subsidence of ~7 cm under 0.47 g shaking. Pore pressures increased markedly near cavities, with peaks exceeding 2.7 kPa. Irregularly shaped and larger cavities further amplified these effects and led to dynamic factors of safety falling below 0.6. In contrast, downstream cavities produced minimal impact. The excellent agreement between experimental and numerical results validates the modeling approach. Overall, the findings highlight that cavity geometry and location are critical determinants of dam safety under both static and seismic conditions.

Grass-covered levees commonly protect river and estuarine areas against flooding. Climate-induced water level changes may increasingly expose these levees to overflow events. This study investigates whether grass-covered levees can withstand such events, and under what conditions failure may occur. Between 2020 and 2022, full-scale overflow tests were conducted at the Living Lab Hedwige-Prosperpolder along the Dutch–Belgian Scheldt Estuary to assess erosion resistance under varying hydraulic conditions and vegetation states. A custom-built overflow generator was used, with instrumentation capturing flow velocity, water levels, and erosion progression. The results show that well-maintained levees with intact grass cover endured overflow durations up to 30 h despite high terminal flow velocities (4.9–7.7 m/s), without structural damage. In contrast, levee sections with pre-existing surface anomalies, such as animal burrows, slope irregularities, surface damage, or reed-covered soft soils, failed rapidly, often within one to two hours. Animal burrows facilitated subsurface flow and internal erosion, initiating fast, retrograde failure. These findings highlight the importance of preventive maintenance, particularly the timely detection and repair of anomalies. Once slope failure begins, the process unfolds rapidly, leaving no practical window for intervention.

Abstract To address the lack of field data regarding the internal properties of landslide dams and to support the development of sophisticated stability indices, multidisciplinary investigations were performed on the Cuejdel Lake landslide dam in the Eastern Carpathians. The combination of electrical resistivity tomography, sedimentary facies mapping, infiltration tests, and geotechnical sampling revealed blocks of preserved stratigraphy embedded in a relatively impermeable sedimentary matrix containing sands and clayey-silt components. Although the eroded dam face shows a heterogenous distribution of sedimentary facies, the hydraulic properties are dominated by a mixture of sand, silt, and clay resulting in a uniformly saturated phreatic zone with permeability values between 1 × 10−7 $$\frac{m}{s}$$ m s . and 1 × 10−8 $$\frac{m}{s}$$ m s . Analyses of a LiDAR survey clarify that the previously described single landslide is a pair of two landslides from which the northern Slide A dammed the Cuejdel Lake. An abandoned spillway path responding to the lowest point of the dam crest indicates erosion due to overtopping shortly after the dam formation. The low permeability resulting from the sedimentary matrix prevented a destruction of the dam by internal erosion during the early formation stages. Although overtopping occurred after the dam initiation, the failure progression towards a dam breach was guided by the seasonal variations of lake water levels. The seasonal decrease of the water level prohibited the advancement of the overtopping related erosion, while the increase of the lake water level in the consecutive wet season led to a stabilization through a spillway along the landslide toe. While valuable for rapid first order hazard assessment, current stability indices are not capable of reproducing the complex stabilization process of the Cuejdel Lake landslide dam, emphasizing the need for integrating facies-based geotechnical parameters and hydraulic variabilities in hazard assessments of individual cases.

The spatial variability of soil seepage parameters is an essential component of the uncertainty of earth dams. This paper presents a method for backward erosion reliability analysis that considers the spatial variability of seepage parameters in earth dams to assess the distribution of the Factor of Safety (FoS) and the initiation probability (Pf). In this study, the Karhunen-Loeve method is used to generate Random Fields (RFs) of soil hydraulic properties, and Monte Carlo simulations (MCS) are used to generate realisations of these RFs, which are then introduced into the numerical model to assess the spatial variability of the seepage analysis results. The hydraulic gradient distribution is compared with the critical hydraulic gradient to assess the FoS and the Pf due to backward erosion at each point of the dam. This study also presents the effect of water level H, permeability anisotropy coefficient ξ, and RFs parameters (coefficient of variation COVKs, correlation length Lh & Lv) on the FoS and Pf of Backward Erosion Piping (BEP). The results illustrate that the initiation probability Pf increases with H, COVKs and ξ. The initiation probability Pf is not sensitive to the vertical correlation length, but may decrease with the horizontal correlation length. Furthermore, the study discusses the potential initiation locations of internal erosion and presents results based on criteria using both local and global hydraulic gradients.

Internal soil erosion caused by water infiltration around defective buried pipes poses a significant threat to the long-term stability of underground infrastructures such as pipelines and highway culverts. This study employs a coupled computational fluid dynamics–discrete element method (CFD–DEM) framework to simulate the detachment, transport, and redistribution of soil particles under varying infiltration pressures and pipe defect geometries. Using ANSYS Fluent (CFD) and Rocky (DEM), the simulation resolves both the fluid flow field and granular particle dynamics, capturing erosion cavity formation, void evolution, and soil particle transport in three dimensions. The results reveal that increased infiltration pressure and defect size in the buried pipe significantly accelerate the process of erosion and sinkhole formation, leading to potentially unstable subsurface conditions. Visualization of particle migration, sinkhole development, and soil velocity distributions provides insight into the mechanisms driving localized failure. The findings highlight the importance of considering fluid–particle interactions and defect characteristics in the design and maintenance of buried structures, offering a predictive basis for assessing erosion risk and infrastructure vulnerability.

Surface erosion involves the removal of soil from ground surfaces, riverbeds, or seabeds by flows or currents. While internal erosion has been widely researched, surface erosion—especially in cohesive soil—remains less explored from a geotechnical perspective. This study examines effects of fines content and stress history on the erodibility of cohesive soils. Using five materials with varying fines contents, key erosion parameters, including erosion coefficient (K<sub>d</sub>) and critical shear stress (τ<sub>c</sub>), were measured in a purpose-built apparatus. The results were correlated with the shear strength under zero normal stress (τ<sub>ds</sub>) obtained from a modified direct shear test. It was found that while τ<sub>c</sub> showed a strong correlation with τ<sub>ds</sub> in soils with varying fines contents, this correlation weakened under stress history effects. In contrast, the correlation between K<sub>d</sub> and τ<sub>ds</sub> remained more consistent for varying fines contents and stress history conditions. Notably, higher fines content did not always enhance erosion resistance, and excessive fines could reduce the erosion resistance. Increasing OCR improved the erosion resistance, with the most notable changes occurring at OCR<=4. Moreover, the stress history effects on soil erodibility were visualized by linking the erosion coefficient to the void index.