Geotextiles, as a type of common filtration material, have broad prospects in emergency rescue of dike backward erosion piping (BEP). To investigate the filtration performance of geotextile in BEP emergency rescue, several experiments were conducted using nonwoven and woven geotextiles to simulate the process of rescuing BEP with geotextiles. The influence of geotextile specifications and types on hydraulic compatibility of the filter system was analyzed, and the clogging mechanism of geotextile during dealing with BEP was revealed at a microscopic level. The results showed that the nonwoven geotextile filter with an equivalent pore size of 0.103 mm had a gradient ratio value of less than 3, and it had a highest flow rate of 260 mL/min. Increasing the thickness and pore size of nonwoven geotextiles within a certain range helped enhance their anti-clogging ability. The main mechanism of clogging in nonwoven geotextiles was the deposition of fine sand particles on their surface, forming a layer of low permeability soil. Plain woven geotextiles experienced severe clogging with a 42% reduction in flow rate, and it was not suitable for rescuing BEP. The clogging mechanism of woven geotextile involved the blocking of horizontal water passages by fine sand particles.

Abstract The renaissance botanical garden of ‘El Bosque’ in Béjar (Salamanca, Spain) presents a pond bounded by a dam in its western part. The latter is formed by two masonry walls interconnected by buttresses. Cubic spaces in between are filled with a variable grain‐size material (silty sand) that allows limited water flow. In recent years, the southern part of the dam has experienced localized and random subsidence that jeopardizes the entrance to part of the garden. To regain access, a proper and reliable diagnosis of the origin, magnitude and relevance of the subsidence must be made. In this regard, we have undertaken a microgravity survey in the dam area to identify places with an anomalous distribution of the filling material in order to foresee further sinking or potential collapsing areas. The precise positioning (2 mm resolution) and accurate terrain correction needed in this kind of high‐resolution gravity surveys (points every 1.5 m) were achieved by creating a detailed digital terrain model (cm resolution) with a remotely piloted aircraft. In addition, we performed three electric resistivity tomography (ERT) profiles at different levels of the garden: (i) on the dam itself; (ii) right on the foot of the dam and parallel to it (5 m below and ∼17 m to the W); and (iii) a bit farther, but also parallel to the dam (8 m below and ∼27 m to the W). The ERT profiles identified high conductivity in water‐saturated areas and determined the paths that rainfall and pond's seepage water follow in the dam and its underground, formed by granites. The geophysical studies were paired with geotechnical analyses of the sunk materials. The study concluded that the thinnest fraction of the dam's filling material (i.e., silts) is being washed away, leaving behind sand with less density and stability, susceptible to collapse. Thus, the observed sinking is related to soil piping, that is to soil internal erosion and compaction issues that force the soil material to re‐adjust geometrically and volumetrically.

During the July 2021 Flood, the main flood defences along the River Meuse in the Netherlands performed well and did not breach. This paper provides an overview and description of the reported incidents related to flood defences, including a few breaches in minor flood defences. The incidents include overflow of embankments, sand boils, internal erosion at structures, and damage to a large weir and an outflow structure. Also, two local flood defences breached: an emergency embankment at Horn and an embankment in Roermond. During the event, the media reported on a dike breach at Meerssen/Bunde, however, after further investigation, it appeared that the concentrated outflow there was fuelled from a forgotten buried culvert.

In zoned embankment dams, horizontal and vertical cracks developing in the upstream-downstream direction for various reasons cause internal erosion, resulting in serious consequences such as dam failure. Hydraulic fracturing is one of the mechanisms that cause these cracks to develop in the upstream-downstream direction. Hydraulic fracturing occurs when the stresses at the upstream face of the core are less than or equal to the hydrostatic stresses originating from the reservoir. The arching phenomenon creates the stress environment in which hydraulic fracturing can develop. In transverse arching, one of the arching types, stress transfer occurs from the core to the transition and shell zones. As a result of this stress transfer, the vertical stresses on the upstream surface of the clay core decrease. This study examines the effect on zoned dam transverse arching behavior in combinations where the geomechanical characteristics of the clay core (Elasticity modulus and Poisson ratio) change, provided that the material characteristics in the transition and shell zones are constant. Numerical analyses were carried out using the finite element method using the maximum cross-section of Çınarcık Dam. As a result of numerical analysis, it was seen that the increase in the elasticity modulus and Poisson ratio values, which are the deformation parameters of the clay core, was effective in reducing the transverse arching potential.

The prediction of railway embankment failure is still a global challenge for the railway industry due to the complexity of embankment failure mechanisms. In this work, the pre-failure deformation and the settlement from abnormal deformation to the final failure were investigated based on earth observation and on-site monitoring with a focus on the deformation stage and failure mechanism of railway embankments. Some new viewpoints are suggested: (1) the differential settlement of ~19 mm revealed via InSAR at the failure region of the embankment may have been caused by internal erosion after rapid drawdown. The cumulative settlement was found to increase with the decline of the lake water level. (2) The railway embankment experienced three phases of primary, secondary, and accelerated creep phases, similar to the evolution of most landslide or dam failures. However, the train loading and seepage force may have aggravated the secondary consolidation, promoting the embankment to enter the accelerated creep phase quickly. The deformation pattern was presented as an exponential curve trend. (3) The formation mechanism of embankment collapse can be summarized as “seepage failure-creep-shear slip-collapse” failure under repeated train loading and rapid drawdown. This work provides some clues for early warnings and for the development of maintenance plans.

Particle erosion in 90-Degree elbow pipe of pneumatic conveying System: Simulation and validation

Effects of pre-shearing stress ratio on the mechanical behaviours of gap-graded soils subjected to internal erosion

The soil piping erosion has been closely related to the soil composition and its dispersive nature. The phenomenon of dispersivity is explained by the property by virtue of which the soil breaks down into their component particles upon exposure to water. Dispersive soils are highly prone to erosion. If the soil at top is hard and soft dispersive clays present at bottom, in presence of seepage water, there are chances for piping erosion to occur. These kinds of process are very common in lateritic terrains. In appearance the normal erosion resistant clays are similar to dispersive clays, they are, in fact, prone to significant erosion and are susceptible to severe damage. Exchangeable sodium present in the soil is the primary cause of dispersivity. Special methods are required to distinguish between dispersive and non-dispersive soils, common soil classification tests are not sufficient. The recommended tests to identify the dispersive clay soils are Crumb test, Double hydrometer test, Pin hole erosion test, and some chemical tests.This paper reports the problems associated with dispersive soils and discuss the results of double hydrometer tests carried out in various piping regions of Kerala along with the stabilization of dispersive soils with lime. Double hydrometer test as per British standards have been used in the present study. Comparative study of the dispersion ratios obtained for various samples shows that the Idukki samples are having more dispersion ratio than other regions. And as the piping was present in those areas the dispersion ratio was expected to be higher than 30%, the lower values obtained can be due to the erosion of dispersive clays in those regions. Effectiveness of stabilization with lime is checked and it was found that the ideal proportion of lime for minimizing dispersion potential is 1%.

Prediction ability of discrete element model of loose granular media subjected to complex loadings

Parametric Analysis on the Erosion and Corrosion Behavior of GRP's Hybrid Composite Pipes Used for the Transport of Petroleum Waste-water

Understanding the mechanism of biofilm distribution and detachment is very important to effectively improve water treatment and prevent blockage in porous media. The existing research is more related to the local biofilm evolving around one or few microposts and the lack of the integral biofilm evolution in a micropost array for a longer growth period. This study combines microfluidic experiments and mathematical simulations to study the distribution and detachment of biofilm in porous media. Microfluidic chips with an array of microposts with different sizes are designed to simulate the physical pore structure of soil. The research shows that the initial formation and distribution of biofilm are influenced by bacterial transport velocity gradients within the pore space. Bacteria prefer to aggregate areas with smaller microposts, leading to the development of biofilm in those regions. Consequently, impermeable blockage structures form in this area. By analyzing experimental images of biofilm structures at the later stages, as well as coupling fluid flow and porous medium, and the finite element simulation, we find that the biofilm detachment is correlated with the morphology and permeability (kb) (from 10-15 to 10-9 m2) of the biofilm. The simulations show that there are two modes of biofilm detachment, such as internal detachment and external erosion.

Rainfall is the main cause of erosion damage in loose slope deposits. During rainfall infiltration, fine particles in the soil mass will move with water infiltration, thus changing the localized particle distribution of the soil mass, which, in turn, causes changes in the pore water pressure and volumetric water content within the slope and ultimately affects slope stability. In order to develop advanced soil and water conservation programs to prevent slope damage, it is crucial to understand and accurately reproduce the particle migration and aggregation characteristics of soils under different rainfall conditions. Therefore, this paper systematically investigates the soil particle migration characteristics of the soil body under rainfall conditions by simulating the internal erosion of the lateritic soil slope body under rainfall conditions via slope internal erosion simulation experiments and experimentally analyzing the migration and aggregation of fine particles in the slope body, as well as the changed rules regarding pore water pressure and volumetric water content at different locations of the slope body with rainfall. The results of this study show that (1) with the infiltration of rainfall, the fine particles in the slope body mainly infiltrate in the vertical direction in an early stage of rainfall; in a later stage, there is vertical downward and down-slope seepage. Therefore, fine particles always gather at the toe of the slope, which leads to relatively high water content and pore water pressure at the toe of the slope, and thus, the slope is always damaged from the toe of the slope. (2) Inside the slope, the fine particles always gather at the smallest pore diameter. With the enhancement of hydrodynamic force, they will be lost again, which leads to a sudden decrease in the local volumetric water content of the slope, and the pore space increases. Then, it is filled with seepage water, which makes the pore water pressure fluctuate or increase. (3) Based on the particle distribution parameter, the present study produced a distribution map of the fine particle content of the slope body under different rainfall intensities and established a model of the dynamic change of fine particles, which improves the understanding of the effect of the change in the fine particle composition of the slope body on the water content and the pore water pressure and may be helpful for the assessment of the initiation of the mudslides.

Internal erosion refers to the movement of fine particles within soil framework due to subsurface water seepage. Existing criteria for assessing internal erosion usually are based on static loading, and the effect of cyclic load is not considered. Additionally, there are limited studies to examine the particle-size distribution and origin of eroded fine particles. This study presents an experimental investigation that examines the impact of cyclic loading on internal stability through a series of seepage tests. The composition and origin of lost particles are quantitatively studied using particle staining and image recognition techniques. With increasing hydraulic gradient, particle erosion progresses from top layer to bottom layer, with a gradual increase in the maximum particle size of eroded particles from each layer. After significant loss of particles, the specimens reach a state of transient equilibrium, resulting in a gradual slowdown of both particle loss rate and average flow velocity. The results indicate that cyclic loading promotes massive particle loss and causes erosion failure of specimens that are considered stable according to existing criteria. The reason is that under cyclic loading, local hydraulic gradients is oscillating, and a larger than average hydraulic gradient may occur, which is responsible for the internal instability. The analysis suggests that existing criteria can provide a reasonable assessment of the relative stabilities of specimens under static loads but fail to capture the stabilities under cyclic loading conditions.

Experimental Investigations on the Evolution of Undrained Mechanical Characteristics of Cohesionless Soils Subjected to Internal Erosion

This work focuses on the mechanisms that trigger internal erosion of the pervious foundation of flood protection dikes. The origin of these permeable layers is generally attributed to the presence of a paleo-valley and paleo-channels filled with gravelly-sandy sediments beneath the river bed and dikes. These layers may extend into the protected area. Visual observations of leaks, sand boils and sinkholes in the protected area testify to internal erosion processes in the underground soil. Local geological conditions are part of the information to be sought to explain these processes: presence of permeable soils and position of interfaces. Results obtained on Agly dikes (France), using two classical geophysical methods (EMI and ERT), were analyzed using cored soils and showed that it is not enough to simply conclude to the presence of backward erosion piping. The possibility of internal erosion, such as suffusion or contact erosion, must also be considered as the cause of leaks, sand boils and sinkholes. As the results obtained are explained by the presence of a paleo-valley and paleo-channels beneath the river bed and dikes—commonly encountered in this context—the methodology presented and the results obtained are likely to be relevant for many dikes.

Microscopic mechanism of the combined effects of confining pressure and fines content on suffusion in gap-graded underfilled soils

Layered deposited-soil slopes are widely distributed in mountainous terrain. The rainfall-induced instability of layered deposited-soil slopes is not only controlled by the unsaturated infiltration process but also by the seepage-induced internal-erosion process within the deposited soils. In this paper, the main physical processes within two-layer deposited-soil slopes under rainfall infiltration are summarized, and a coupled seepage–erosion finite element model is established to analyze the interactions between the rainfall infiltration process and the internal-erosion process within layered deposited-soil slopes. This finite element model was validated by simulating the coupled seepage–erosion process in a one-dimensional layered soil column. Then, serials of two-dimensional coupled seepage–erosion simulations were conducted to investigate the rainfall-induced seepage–erosion patterns, as well as their impact on the stability evolution of the layered deposited slopes. It was shown that the rainfall-induced seepage–erosion accelerate the water infiltration into the slope and facilitate the generation of subsurface stormflow near the layer interface, which will weaken the soils around the layer interface and accelerate the slope failure process inevitably. Special attention should be paid to the rainfall-induced seepage–erosion effect when evaluating the stability of layered deposited-soil slopes.

An innovative application of fine marble dust for the construction industry to mitigate the piping, internal erosion and dispersion problems of sodium-rich clays

Suffusion behavior of crushed calcareous sand under reversed cyclic hydraulic conditions

Hybrid regularization and weighted subspace algorithms with random forest model for assessing piping erosion in semi-arid ecosystem