Seepage Erosion Research Articles

Experimental Assessment on the Internal Instability of Broadly Graded Silty Sand

Suffusion can occur when fine particles are under low effective stress and free to travel through constrictions between coarse particles, and sufficient seepage forces move the fine particles through the voids. Generally, gap-graded soils, which are a binary mixture of two distinct particle sizes, are susceptible to suffusion. Such soils show clear manifestations of suffusion, such as a significant quantity of fine particles discharged and an increase in permeability and void ratio. Therefore, in previous studies on seepage erosion problems, gap-graded soils were mostly utilized as the target soil. However, it is not clear whether the broadly graded soils, the fill dam materials in South Korea, are susceptible to suffusion according to the existing criteria and previous research. Additionally, experimental studies on broadly graded soils have rarely been conducted, especially in terms of hydraulic conditions. Therefore, a deeper understanding of the suffusion progress on broadly graded soils under various hydraulic conditions (hydraulic gradients) is required. In the present study, suffusion tests were performed on gap-graded andbroadly graded soils with different relative densities by using the newly developed suffusion test apparatus. During the test, the hydraulic gradient was increased stepwise, and the occurrence and progress of internal erosion were analyzed based on the amount of discharged soil and the coefficient of permeability. In contrast to gap-graded soils, the test results for broadly graded soils showed a continuous reduction in k before the initiation of erosion. At the onset of internal instability, sudden increases in k and soil discharge occurred under a relatively high hydraulic gradient. Additionally, a series of seepage tests on broadly graded soils showed that the higher the relative density, the higher the hydraulic gradient required to reach an unstable state.

Modeling dam deformation in the early stage of internal seepage erosion – Application to the Teton Dam, Idaho, before the 1976 incident

Internal seepage erosion of dams is hidden from view and can cause unanticipated dam failure and calamity. Recognition of dam deformation associated with internal erosion may identify the occurrence of internal erosion and provide early warning to the public on the oncoming failure; but quantitative analysis of dam deformation due to internal erosion is currently lacking. In this study we formulate the early stage of internal erosion and dam deformation by using a numerical model that couples several aspects of the problem, including groundwater flow, erosion and transportation of solid particles, and deformation of the solid skeleton. We apply the model to the Teton Dam of Idaho, which failed in 1976 due to internal erosion. Our simulation shows that the early stage of internal erosion degrades the stiffness of the dam and produces recognizable ground subsidence. It increases porosity and permeability and accelerates flow and internal erosion in a positive feedback process. The predicted magnitude of the surface deformation of the dam during the early stage of internal erosion ranges from several cm to tens of cm that may be detectable with current land survey and space geodesy. Detection of such deformation during the early stage of the internal erosion of the dam should provide sufficient early warning to the oncoming failure. Our result suggests that continuous geodetic monitoring may be an effective measure to detect the occurrence of internal erosion, together with an early warning system, may help to mitigate dam failure and the loss of life and properties.

Prediction of water–mud inrush hazard from weathered granite tunnel by an improved seepage erosion model

Prediction of water–mud inrush hazard from weathered granite tunnel by an improved seepage erosion model

Optimization design of a large-scale seepage control system at a high arch dam site

The Baihetan Hydropower Station, located in the lower reaches of Jinsha River in southwest China, is the second largest hydropower station in the world. The site is characteristic of extremely complex geological and hydrogeological conditions, with fractures, faults, and shear zones that make water tables wedge-shaped. A large-scale seepage control system that contains grouting curtains covering an area of 780,000 m2 and 12,300 drainage holes, together with concrete plugs, were designed to control the seepage in the dam foundation and in the underground powerhouse areas as the reservoir water level will be raised by 225 m during operation. How to assess the performance and optimize the design of seepage control system becomes a key technological issue in the design and construction of this project. In this study, a three-dimensional finite element model that well represents the site conditions is established. The drainage holes are modelled with a substructure technique and the seepage field is solved with the variational inequality method of Signorini’s type. A procedure is proposed to optimize the layout of the seepage control system by taking the amount of leakage, the distribution of uplift pressure, the risk of seepage erosion and cost into account. Numerical results yield the appropriate parameters for the seepage control system, including the extension and depth of grouting curtains, and the spacing of drainage holes. With these optimized parameters, the seepage control system is effective in lowering the phreatic surface and limiting the amount of leakage at the dam site.

Visual Simulation of Soil-Structure Destruction with Seepage Flows

This paper introduces a method for simulating soil-structure coupling with water, which involves a series of visual effects, including wet granular materials, seepage flows, capillary action between grains, and dam breaking simulation. We develop a seepage flow based SPH-DEM framework to handle soil and water particles interactions through a momentum exchange term. In this framework, water is seen as a seepage flow through porous media by Darcy's law; the seepage rate and the soil permeability are manipulated according to drag coefficient and soil porosity. A water saturation-based capillary model is used to capture various soil behaviors such as sandy soil and clay soil. Furthermore, the capillary model can dynamically adjust liquid bridge forces induced by surface tension between soil particles. The adhesion model describes the attraction ability between soil surfaces and water particles to achieve various visual effects for soil and water. Lastly, this framework can capture the complicated dam-breaking scenarios caused by overtopping flow or internal seepage erosion that are challenging to simulate.

Hydro-mechanical behaviour of soil experiencing seepage erosion under cyclic hydraulic gradient

Numerous incidents and failures of earth slopes, dykes, levees and embankment dams are caused by internal erosion. At a time of global climate change, rapid pore-water pressure changes in soil masses are frequently induced by extreme rainfall, storm surges, waves, flash floods and so on. Under such complex cyclic hydraulic conditions, the soil erodibility, hydraulic conductivity and subsequent stress–strain behaviour may differ from those under the monotonic seepage condition, and are still poorly understood. In this study, preliminary laboratory tests have been conducted to investigate the development of internal erosion and changes in hydraulic conductivity under one-way cyclic seepage, and the post-erosion stress–strain behaviour. Representative internally stable and unstable soils were tested. The effects of mean hydraulic gradient and cyclic gradient amplitude were investigated in detail. Results show that the erosion development is significantly influenced by both the initial grain size distribution and the pattern of imposed cyclic hydraulic gradient. The cyclic seepage promotes the loss of fine particles and leads to larger hydraulic conductivity. For the internally unstable soil, the eroded soil mass and hydraulic conductivity increased significantly with increasing cyclic gradient amplitude. Nevertheless, the internally stable soil experienced a small amount of particle loss, even under large cyclic gradients. For both types of soil, a larger cyclic gradient amplitude corresponds to a stronger post-erosion contractive shearing behaviour and a smaller critical friction angle.

Investigation of drainage function of geosynthetics for basal-reinforced embankments

This study investigates the behaviour of basal-reinforced embankments under seepage flow. For this purpose, physical embankment models with dimensions of 195 cm long, 100 cm wide and 110 cm high were constructed in the laboratory. The seepage gradient within the embankment was generated by applying a constant water head of 100 cm at the water compartment located behind the models. The unreinforced embankment experienced seepage erosion at the toe section which triggered deep-seated global failure. Due to the limited transmissivity of the non-woven geotextile, the geotextile-reinforced embankment exhibited similar pore-water pressure distribution to that of the unreinforced embankment, which resulted in lateral spreading failure between the base of the embankment and the non-woven geotextile. In contrast, the geocomposite drain, which has a higher in-plane flow capacity compared to that of the geotextile, significantly alleviated the pore-water pressures within the embankment. The behaviour of the physical models was verified numerically by variably saturated flow modelling conducted for a wide range of in-plane permeabilities for the basal reinforcement. The effect of increasing in-plane permeability of the basal reinforcement layer on pore-water pressure reduction was quantified irrespective of the geosynthetic type.

Experimental study on the process of overtopping breach of concrete-faced sand-gravel dam

A concrete-faced sand-gravel dam (CFSGD) is likely to experience a dam breaching accident once there is leakage through the concrete face slab joints or overtopping of the dam. This study aimed to examine the physical process of a CFSGD overtopping breach and considered the influence of the failure of the vertical joint water barrier. The similarity criterion of the model test was deduced and the face slab that met the requirements of the model test was prepared. Through flume model tests, the process of overtopping dam breach was divided into four stages, i.e. Stage I, seepage erosion stage, Stage II, gradual erosion stage, Stage III, violent dam breach stage and Stage IV gradual stabilisation stage. The results showed that under the influence of seepage erosion, the initial breach of the dam occurred at the upper edge of the seepage surface of the downstream slope. The flow process line of the breach was of a ‘lean and high’ type, and there was a clear increase in the average rate of undercutting and horizontal expansion of the breach, highlighting the important influence of the early seepage erosion stage on the later dam breach process.

Influences of buried depth and grain size distribution on seepage erosion in granular soils around tunnel by coupled CFD-DEM approach

For tunnels built in the saturated silty sand ground, fine particles may be migrated into tunnels through seams of tunnel segmental joints and then seepage erosion is triggered, which may induce ground settlement. However, the process from fine particles erosion to the stress redistribution and soil properties’ change surrounding the tunnel and ground settlement has not been clarified up to now. For this purpose, five numerical tests of seepage erosion in granular soils around the tunnel are conducted using the Computational Fluid Dynamics and Discrete Element Method (CFD-DEM) coupling method. The influences of buried depth and grain size distribution (GSD) of gap graded soils (mainly controlled by the fines content and mean particle size ratio from coarse to fine) on the seepage erosion around the tunnel are investigated. Eroded mass, fines loss mode, surface vertical displacement, stress redistribution, fabric anisotropy, soil behavior and water pressure around the tunnel during the seepage erosion process for five tests are presented and compared. The following results can be upscaled to the practical tunnel engineering, such as: (1) the number of fines loss, the eroded zone and the ground settlement increase with buried depth and mean particle size ratio; (2) the earth pressure near the crack significantly increases due to the stress redistribution induced by fines loss, and the stress redistributed area expands with buried depth; (3) the strength and stiffness of granular soils around the crack are significantly reduced by the seepage erosion. All results revealed that the CFD-DEM simulations provide a new sight on understanding the mechanics of tunnel seepage erosion from a microscopic perspective.

Numerical Simulation of Channelization Near the Wellbore due to Seepage Erosion in Unconsolidated Sands during Fluid Injection

The channels may be formed in the unconsolidated sands reservoir due to formation failure during high-pressure water injection or frac-packing. Based on the continuum mechanics, a mathematical model has been established to simulate the formation process of big channels in unconsolidated sands reservoir during fluid injection. The model considers the effect of reservoir heterogeneity, solid particles erosion, and deposition. The dynamic formation process of channels around the borehole and its influencing factors are analyzed by this model. The results indicate that the seepage erosion plays a very significant role in the formation of the channels during fluid injection for the unconsolidated sands with extremely low strength. The formation of the channels is closely related to the duration of fluid injection, injection pressure, reservoir heterogeneity, formation plugging, and critical fluid velocity. The long channels are more likely to form as injection time increases. Higher injection pressure will lead to higher flow rate, thus eroding the solid particles and forming big channels. The increase of the rock strength will enhance the value of critical fluid velocity, which makes it difficult for the occurrence of erosional channelization. The near-wellbore damage of the formation will decrease the flow rate, and the preferential flow channels are less likely to be induced under the same injection pressure when compared with undamaged formation. In addition, we also found that the reservoir heterogeneity is essential to the formation of preferential flow channels. The channels are especially prone to be formed in the regions with high porosity and permeability at the initial time. The study can provide a theoretical reference for the optimal design of high-pressure water injection or frac-packing operation in the unconsolidated sands reservoir.

Correction to: A new method to prevent seepage erosion of loess slope toe using the combination of filter pipe and siphon drainage

A Correction to this paper has been published: https://doi.org/10.1007/s10064-021-02204-7

A new method to prevent seepage erosion of loess slope toe using the combination of filter pipe and siphon drainage

Long-term agricultural irrigation on the top of the loess tableland will cause the toe of the slope to be eroded by seepage, which will induce repeated landslides. The coupled filter pipe and siphon drainage method (F&S method) is a new drainage method that combines existing methods and materials to focus on the mechanism by which seepage erosion occurs at the toe of the loess slope. The method was tested in the laboratory and the Heifangtai landslide group in Gansu Province, China. By testing the filtered water that was siphoned out during the tests and assessing the geomorphological changes after the field test, it was apparent that the F&S method effectively prevented the loess slope toe from being eroded and transported by the seeping groundwater. The drainage data and monitoring the groundwater level showed that the F&S method has a sensitive response capability and can automatically control the level of the groundwater. The results of the experiment with the physical model indicated the range of the influence of the F&S method on the loess, and this information, combined with the results of the field test, can be used to optimize the layout of F&S devices. The research showed that, compared with the methods that commonly are used to treat loess landslides, the F&S method has the advantages of strong pertinence, quick effect, simplicity, and low cost. This method is suitable for additional applications in loess areas.

Experimental Study on Monitoring of Dike Piping Process Based on Acoustic Emission Technology

Acoustic emission (AE) is employed in this study to monitor piping failure process in the dike subjected to varied head action. Piping is the main reason for the seepage failure of dikes and dams, and the AE characterization of piping process is investigated. The laboratory experiments and data analyses were carried out using specially designed physical model and data acquisition systems. The monitored data were analyzed using four methods, namely, AE ringing count, fractal dimension, frequency domain analyses and b value. The analysis results showed that the piping failure process can be divided into 3 phases: seepage erosion, piping generation, and piping development. In different stage, the activity of the AE signals is related to seepage flow and seepage pressure. Based on the fractal dimension and waveform energy spectrum distribution analysis in the entire process of piping failure, the measured acoustic signals in the test can reflect both a seepage-induced and a soil-seepage induced AE. The AE ringing count fractal dimension and waveform energy spectrum can be used as new index monitoring the occurrence and development of piping. The abrupt change of AE fractal dimension and AE energy spectrums curve with time can be considered as the precursor to piping occurrence and piping development. What’s more the b value of the AE signal can be used to describe the piping state.

Experimental investigation on seepage erosion of the soil–rock interface

Internal erosion under seepage flow affects the hydraulic and mechanical behavior of the soil, which is one of the most important factors of geological disasters. Due to that the soil–rock interface can be the potential preferential seepage channels commonly, the characteristics of erosion are more significant and hazardous at the soil–rock interface. In this study, a series of laboratory experiments are performed to investigate the failure mechanism and evolution of interfacial seepage erosion. The influences of two essential influence factors (i.e., the confining pressure and the roughness of the interface) are investigated by comparing the seepage velocity, hydraulic conductivity, failure hydraulic gradient, and failure hydraulic shear stress in experiments. Furthermore, the failure pattern of interfacial seepage erosion is particular investigated by the CT scanning. The interfacial seepage erosion tests indicate that the interfacial seepage erosion shows a three-phase progressive failure as the hydraulic gradient increases and the hydraulic conductivity decrease with the progress of suffusion in the initiation phase. The increase of confining pressure leads to the increase of failure hydraulic gradient. The results of CT scanning show that the roughness of the soil–rock interface significantly affects the size and shape of resulting zone of erosion.

Enzyme induced carbonate precipitation for soil internal erosion control under water seepage

Seepage induced internal erosion in earth dams, dikes, and their underlying soil strata may cause destruction of earthen structures and flooding of lowland regions. In this study, efforts were made to evaluate the use of the enzyme induced carbonate precipitation (EICP) method for the control of internal erosion under water seepage. Gap-graded soils with 15% fine particles were improved by the EICP method for 1 to 5 passes. In each pass of treatment, 1.5 pore volume treatment liquid containing soybean-derived urease and 0.5 mol/L equimolar urea-calcium chloride was applied to the soil sample. After the EICP improvement, the soil samples underwent seepage erosion of stepwise-increased flow rates. In addition to the EICP-treated soil samples, an untreated soil sample and a soil sample treated by the microbially induced carbonate precipitation (MICP) method were also tested for comparison. The results showed that, in terms of the amount and rate of eroded fine particles, the EICP soil samples had stronger resistance against seepage erosion as compared with the MICP sample and the untreated soil sample. The erosion control effects also improved with treatment passes. The EICP improvement was also effective in reducing the axial deformation of soil. The level of axial deformation was roughly consistent with the amount of fine particles eroded. The calcium carbonate distribution was relatively uniform in the EICP samples compared with the MICP sample. The results presented in the paper show that the EICP method is a promising solution for the control of seepage induced internal erosion in soils.

Effect of Alkali Seepage Erosion on Physical and Mechanical Properties of Laterite

Using a modified permeameter, laterite samples that were corroded and permeated by alkaline solutions at different concentrations for varying amounts of time were subjected to triaxial compression tests, chemical composition analysis, particle composition tests, and microstructure analysis. The results showed that the strength parameters c, φ, and K of the laterite samples that were corroded by alkaline‐solution permeation were reduced with increasing corrosion time and alkaline‐solution concentration. The alkaline‐solution corrosion had a minor effect on the strength parameters n and Rf. The contents of Al2O3 and Fe2O3 in the laterite fluctuated and decreased with increasing alkaline‐solution concentration and corrosion time. There were no distinct patterns in the relationships between the SiO2 content and the increases in the alkaline‐solution concentration and corrosion time. Due to the corrosion during the alkaline‐solution permeation, the content of clay particles increased with increasing time and concentration of the alkaline solution. After the permeation with the alkaline solution, the soil particles became smaller and were arranged in an ordered state. The analysis suggested that the permeation effect of the alkaline solution changed the chemical composition of the laterite and the connecting strength of the soil particles, resulting in changes in its physical and mechanical properties.

Source-to-mainstream: Hydrochemical water changes in a channel head in the young glacial area (Pomeranian Lakeland, Poland)

A channel head is a zone where hydrological changes occur that shape the chemical features of water, during the final stage of underground flow and the beginning of the surface water cycle. The study aims were as follows: (i) to characterise spatial water chemistry patterns; (ii) to establish the role played by the hyporheic zone in the chemical transformations associated with the groundwater that supplies the first-order stream; and (iii) to identify the factors that control the chemical composition transformations that occur in headwater alcoves. The analysis was performed on three sets of samples taken at the Żarnowo channel head situated in the young glacial landscape of the Parsęta drainage basin (NW Poland).The performed hydrochemical measurements showed that the waters found in the alcoves displayed a mosaic pattern, with spatial variability in the levels of trace metals and nutrients. In turn, geogenic ions featured in the mineralogical-petrographic compositions of deposits found in headwater catchments, such as Ca2+, HCO3−, Mg2+, and Na+, showed low temporal variability and small differences among the various sampled headwater alcoves. These results indicated that the majority of spatial variance associated with the chemical composition of water is driven by the transformation of groundwater discharges in the hyporheic zone. The locations of hydrochemical transformation hotspots can be explained by the influences of critical physical variables, such as the intensity of seepage erosion, sediment texture, bottom microtopography, groundwater discharge characteristics, water temperatures, and the diversity of groundwater-fed vegetation. Hydrochemical studies performed in the ground- and surface-water contact zones within a channel head can identify the underlying causes of changes to water chemistry, which, in turn, can facilitate the protection of water resources against unfavourable changes that may affect the water quality at the headwater catchment.

Experimental study on seepage erosion induced by pipeline damage under full pipe flow condition

Experimental study on seepage erosion induced by pipeline damage under full pipe flow condition

Amphitheatre‐headed canyons of Southern Utah: Stratigraphic control of canyon morphology

AbstractAmphitheatre‐headed canyons are common on Earth and Mars and researchers have long sought to draw inferences about canyon‐forming processes from the morphology of canyon heads and associated knickpoints, often suggesting that amphitheatre heads indicate erosion by groundwater seepage erosion. However, the conditions and processes that lead to amphitheatre‐headed canyon formation have been debated for many years. We consider two hypotheses that attribute the amphitheatre‐headed canyon formation to fluvial erosion of strong‐over‐weak stratigraphy or, alternatively, groundwater spring discharge and seepage erosion. A spatial analysis of canyon‐form distribution with respect to local stratigraphy along the Escalante River and on Tarantula Mesa, Utah indicates that canyon form is most closely related to variations in local sedimentary rock strata, rather than inferred groundwater spring intensity. Lateral facies variations that affect the continuity of strong layers can induce or disrupt the formation of amphitheatres. Furthermore, we find that amphitheatre retreat rate is dictated by the interaction of fluvial processes downstream of the amphitheatre headwalls and stratigraphy, rather than waterfall and groundwater processes that likely importantly influence headwall form. We conclude that fluvial erosion of strong‐over‐weak stratigraphic layering alone is sufficient to form amphitheatres at knickpoints and canyon heads. Thus, we re‐affirm that formation process should not be inferred from canyon‐head morphology, particularly where a strong‐over‐weak layering is known or plausible. © 2020 John Wiley & Sons, Ltd.

A Coupled Nonlinear Flow Model for Particle Migration and Seepage Properties of Water Inrush through Broken Rock Mass

A large number of statistics indicate that broken rock mass always transforms into a flowing channel and leads to water inrush disasters in mining engineering, such as fault, karst, and strongly weathered rock mass. During the process of water inrush, the structure of the broken rock mass is constantly changing due to seepage erosion under high-velocity flow. Therefore, it is of vital importance to quantitatively evaluate the flow behavior of the water inrush related to the seepage erosion in order to prevent or reduce the risks. This study described a coupled nonlinear flow model, which couples the high-velocity seepage, the small particle migration, and the evolution of the broken rock mass structure. The model was verified firstly for simulation of nonlinear flow behavior by comparing with the traditional one. Then, the proposed model was used to simulate the evolution of particle migration and seepage properties of the water inrush through broken rock mass by a numerical case. The simulation results generally agree well with the existing experimental results. The simulations indicate that small particle migration causes the unstable characteristics of the seepage and the heterogeneity properties of the broken rock mass, which lead to the nonlinear flow behavior of the water inrush in both time and space. From a different perspective, it also indicates that the proposed model is capable of simulating the interaction of high-velocity seepage, small particle migration, and evolution of broken rock mass structure in the process of water inrush.