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In order to study the impact of internal erosion at the scale of an engineering structure, a hydro-mechanical continuous modelling approach considering suffusion is needed. It requires a relevant mechanical model for granular soils considering the f c -dependency ( f c : fines content) and a hydraulic model for suffusion to control the changes in t...
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... provides a user subroutine option (UEL) that allows users to define a new type of element with the user's governing equations and degrees of freedom (DOFs). The global calculate-flow of ABAQUS with the call of UEL subroutine is shown in Figure 6 where the part 'Call UEL' was developed in this study. In general, Abaqus/UEL solves the overall system of non-linear equations by Newton's method: ...
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... Le tassement dû à l'instabilité mécanique peut se produire instantanément lors d'une érosion importante (lorsque le sol est saturé), ou ultérieurement, lorsque le sol sec précédemment érodé est à nouveau soumis à une saturation. Bien que des fontis soient observés en pied de digues en milieu non karstique (Van et al., 2022), l'origine de ces phénomènes est encore difficile à expliquer (Garner et Fannin, 2010) et leur modélisation reste complexe (Yin et al., 2023). À notre connaissance, il n'existe pas d'étude à ce jour permettant d'expliquer l'apparition d'un fontis dans le sol de fondation d'une digue fluviale tenant compte des conditions géologiques à différentes échelles. ...
Ce travail porte sur les mécanismes physiques à l’origine des processus d’érosion interne dans les sols de fondation des digues de protection contre les inondations. La présence de matériaux perméables est le plus souvent associée à la présence d’une paléo-vallée comblée de sédiments alluviaux sous le lit de la rivière et sous les digues ou de paléo-chenaux sableux pouvant s’étendre au niveau de la zone protégée. Le cas des digues de l’Agly montre que plusieurs processus d’érosion interne doivent être pris en compte pour décrire ces phénomènes : l’érosion régressive, l’érosion de contact et la suffusion. L’utilisation combinée des méthodes d’induction électromagnétique (EMI) et de tomographie de résistivité électrique (ERT) est une solution rapide et peu coûteuse qui permet d’imager le sol et de fournir la géométrie des différentes couches. Combinées à des sondages carottés, les résultats obtenus permettent de localiser la profondeur des interfaces et de mettre en évidence plusieurs scenarii possibles d’apparition de résurgences, de sand-boils et de fontis en bordure de digue, ou au niveau du val protégé.
... The major fields of connected to microfluidics are: molecular analysis, biodefence, molecular biology, and microelectronics (Tamayol et al., 2011a). With advances in microfluidics and microfabrication techniques, flow through microfluidic model in describing the porous media has become an area of great interest (Wan and Wilson, 1994;Bazylak et al. 2008), such as flow rate and interface wettability impacts on immiscible displacement (Conn et al., 2014;Hu et al., 2018;Chen et al., 2023), fines migration and pore clogging (Pozrikidis, 1994;Auset and Keller, 2004;Cao et al., 2019;Yang et al., 2020a;Yang et al., 2020b;Yin et al., 2023), as shown in Fig. 1. There is no doubt that using a microfluidic model to study permeability of porous media shows great potential. ...
In this study, permeability of structured porous media with microfluidic model is experimentally and numerically determined, and compared with the classic Kozeny-Carman (KC) equation. The Reynolds number () varies from 0.83 to 142.98. It is observed that the threshold of the Reynolds number is 1. When is below the threshold, the permeability is independent of the Reynolds number. When is over this threshold, the viscous force plays a dominant role and the permeability decreases with the Reynolds number increment. The permeability also rises with the diameter increment. With the same micropillar diameter, the microfluidic model with triangular pillar arrangement yields lower permeability than that with square pillar arrangement. The tortuosity obtained by numerical simulation in the triangular-arrangement model is higher than that in the square-arrangement model. Based on the arrangement of micropillars, a tortuosity model is proposed for quasi-two dimensional microfluidic models. There is an inverse relationship between permeability and tortuosity. In addition, permeability generated by numerical simulation is consistent with that obtained experimentally. However, permeability estimated by the classic KC equation roughly agrees with experimental results when the porosity is between 0.50 and 0.60. A model proposed in this study is suitable for predicting the permeability of microfluidic models. Furthermore, anisotropy induced by the tilt angle () of a model rectangular micropillar arrangement causes preferential flow and decreases the effective porosity. When the tilt angle increases from to , the tortuosity declines from 2.04 to 1.03, causing the permeability to rise from to .
... For example, Ke and Takahashi (2014b) investigated the fine particle loss patterns and PSD variations of saturated cohesionless soils under different stress states by conducting percolation tests. Yang et al. (2019) and Yin et al. (2020) established a fourconstituent continuum model utilizing the porous continuum medium theory to investigate particle migration during internal erosion. Shire and O'Sullivan (2013) applied the discrete element method to provide a micromechanical explanation for internal erosion and visualize the loss of fine particles. ...
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 destitution and origin of eroded fine particles. This work 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. 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.
... Settlement due to mechanical instability can occur immediately during significant erosion (when the soil is saturated), or later, when the previously eroded soil is dry and subject to saturation. Although sinkholes are observed on dikes in a non-karstic setting [7,8,24,25], the origin of these phenomena is still difficult to explain [26] and their modeling is complex [27]. Up to now, no studies have been proposed to explain their formation in foundation soils of river dikes that consider local geological conditions. ...
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.
... The suffusion phenomenon is a long-term seepage problem that can induce changes in the particle size distribution, porosity and hydraulic conductivity of the soil [38]. Subsequently, progressive degradation of the mechanical properties of the soil may occur, then the internal stability of the soil is impacted [39,56,57], which may be responsible for crack-filling in zoned dams [10,11], landslides [25,34], land subsidence [42,[48][49][50], and even ground collapse [45,47]. Correia Dos Santos et al. [10] proved that the content of fines in filter material at upstream plays important role in the internal erosion for crack-filling in zoned dams under horizontal seepage. ...
Suffusion is a typical kind of internal erosion that changes the permeability property of soil without destroying its structure. A horizontal laboratory test was conducted to analyze the permeability property variation in sandy soil caused by suffusion, and the content of fine sand (Rf) varied from 5 to 25%. Water-level along the seepage path is monitored, and the average hydraulic conductivity of the whole experimental soil (kav) and hydraulic conductivity between two adjacent monitoring tubes (kij) were obtained. The suffusion process experienced diffuse, strong and gentle-migration phases temporally according the variation tendency in kav. The rate of change in kav (Rav) enhanced after suffusion, and the critical value of Rf resulted in the largest variation in Rav was 11.8%, and this conclusion was verified by a discrete element method, in which the corresponding value was 12.2%. According to the variation in Rf along the seepage path, three areas were divided as the runoff, transited and accumulated areas spatially. Moreover, values of the rate of change in kij (Rij) in the runoff and the accumulated areas were much larger than that in the transited area, which were resulted from loss of fine sand, rebound of water-level and comprehensive effect of migrated and accumulated fine sand.
... This paper discusses the selection of low viscosity pore fluids, the experimental procedures, and the results of saturation front movement and fine movements for silt-sized particles of approximately 50 µm diameter. Suggestions for the future development of the methods are presented, which can support in turn the development of constitutive models that are being proposed to predict fine migration (e.g., Yin et al. [36]). These local measurements are important for validating numerical models of multiphase flow in porous media, as well as for linking observations to coupled processes, such as multiphase flow and the mass transfer between fluids. ...
The cyclic liquefaction of soils and associated mud-pumping can lead to costly repairs of roads, railways, and other heavy-haul infrastructure. Over the last decade, several laboratory studies have been conducted to investigate these phenomena, but, due to the opacity of soil, the typical experimental observations of cyclic liquefaction have been limited to post-test observations of fine movement and the data of water pressures and soil settlements. In this paper, we show how partially transparent soil models can be used to provide the visualization of a moving saturation front and that fully transparent models can be used to observe fine migration during the cycling loading of a soil column. The changing saturation degree was tracked using a correlation between the degree of saturation, soil transparency, and grayscale image values, while particle movements of fines and larger particles were measured using a small number of fluorescent particles and particle tracking velocimetry. Another innovation of the work was in using mixtures of ethyl benzoate and ethanol as a low-viscosity pore fluid with the refractive index matching the fused silica soil particles. The benefits and challenges of these visualization tests are discussed.
... seepage velocity or hydraulic gradient). Table 1 summarises common erosion/deposition laws [22,[79][80][81]. The predictive capability of these erosion/deposition laws in the current five-phase model will be investigated later in Section 4. Finally, to complete the proposed governing equations for coupled seepage-erosion and flow-deformation in unsaturated/saturated porous media, a robust constitutive model capable of describing the influence of suction and mass loss on the overall shear strength of soils is required, and this will be discussed in the next section. ...
... Yang et.al. [22,79] Sterpi [80] Cividini et al. [81] 2 ̂= (1 − ) | | Vardoulakis et al. [14] 3 ̂= | | Khalil et al. [84] 3 ̂= (1 − ) | | 2 Steeb et al. [16] Notes: , , are material parameters; is current fines content; ∞ is the ultimate fines; 0 is the initial fines content; ∞ * is the ultimate fines content under reference velocity; is hydraulic gradient; is current time; a, b, c, d are constants; and | | is the absolute value of Darcy's flow velocity. ...
Seepage-induced internal erosion and failure in unsaturated/saturated porous media is challenging for computational simulations as they involve the behaviour, interactions (solid, air, water) and transformation (fluidization and deposition of fines grains) of different phases. Tackling this challenging problem requires correct mathematical descriptions of phase interactions and transformation together with a robust computational framework, both of which are addressed in this paper. The new mathematical model and coupled governing equations based on the continuum mixture theory enable the use of a single set of SPH particles for the descriptions of behaviour, interactions and phase transformation of all five phases of the porous media (soil skeleton, erodible fines particles, fluidised particles, water, and air), including the effect of both saturation and erosion on the shear strength of porous media. A fully explicit and stabilised SPH framework that allows accurate SPH approximations of spatial gradients is proposed for the numerical solutions of coupled governing equations. The proposed computational framework performs well in benchmark tests against available analytical and numerical solutions and achieved reasonable agreements with experiments. Numerical results obtained from the predictions of seepage-induced erosion and failure demonstrate that the proposed computational framework is efficient for addressing challenging problems involving coupled flow-deformation, seepage-induced internal erosions, and large deformation failures of unsaturated/saturated porous media.
... The mechanized excavation using tunnel boring machines (TBMs) has become the prevalent choice for the construction of underground or underwater tunnels [23,44]. An excavation with TBM is characterized by numerous complex interactions between the soil and TBM components, including the face support, tunnel segment assembly, tail void grouting, and so forth [18]. ...
During the tunnel boring machine-based tunnelling, the grout loss caused by the grout penetration and filtration in sandy soils is a complicated multiphysics process. In this study, a novel coupled hydro-mechanical modelling approach based on mixture theory is developed and implemented into a finite element code, which can qualitatively simulate the transport of grout in the soils around the tail void of the TBM tunnel, as well as predict the ground deformation induced by tunnelling and backfill grouting. Using the proposed approach, the time-dependent grout penetration area, grout loss, variation of soil porosity due to grout filtration and the ground deformation are identified. The effects of five key variables including grout pressure, duration, rheological property, filtration in soil mass and hydraulic conductivity of the soil are simulated. The results reveal that to reduce the ground disturbance and grout loss of TBM tunnelling in highly permeable soil, the grout pressure should be increased and the grout time reduced. In addition, grout materials with large permeability, dehydration and hardening rate are recommended.
... Mixtures of coarse-grained soils with fines (gap-graded soils) are commonly encountered in various geological systems and engineering problems, and the important influence of fines content (and type) has been recognized in many previous studies, particularly referring to large deformation behavior [30][31][32][33][34][35][36], leading to the development of constitutive models as proposed by many researchers [37][38][39][40][41] or the study of internal erosion which is of major interest in geomechanics problems [42][43][44][45][46]. Several attempts have been made to incorporate the effect of fines content into predictive/constitutive models of small strain shear modulus [47][48][49][50][51][52][53][54][55] and to provide insights into the fundamental role of fines portion on the behavior of granular materials [56][57][58]. ...
Sand-clay mixtures are often encountered in natural deposits and compacted soils in earth structures in the form of gap-graded soils. They commonly display anisotropic fabric which markedly influences their wave propagation and mechanical properties. In this study, a comprehensive experimental program is carried out to thoroughly examine the influence of the inclined bedding plane and clay type on the small strain shear modulus (Gmax) of granular soils mixed with various portions of low and high plasticity fines, controlling in this way the double diffuse layer of the microparticles. To this end, cylindrical samples containing different fines contents are prepared with their corresponding optimum water contents and maximum dry densities in a standard proctor mold. Undisturbed specimens are then extracted by the continuous coring method and wave propagation tests with bender elements are applied at different angles with respect to the bedding plane (α- direction), evaluating in this way shear wave velocity and Gmax. The test results suggested that α-direction has a significant influence on Gmax of sand-clay mixtures and this influence is amplified at lower fines contents and higher confining pressures. Mixtures of sand with high plasticity clay are observed to have lower degree of anisotropy compared to those containing low plasticity clay, specifically at lower confining pressures. The contribution of fines in the load carrying structure of the solid skeleton decreases for high plasticity clays; the phenomenon which is primarily attributed to the thick diffuse double layer of the microparticles; this trend becomes more pronounced at higher contents of fines inclusion where the sand-in-fine structure dominates. A previously proposed expression for sands is rectified and extended so as to develop a Gmax model of sand-cohesive clay mixtures taking into account the bedding plane direction. Mircomechanical-based interpretations are further elaborated considering the intervention of the microparticles on the contact response of sand grains altering their normal and tangential contact behavior, so as to supplement the findings, from the wave propagation tests, with multi-scale insights.
... 35,36 The CSL translation has been simulated differently in previous studies. 2,[37][38][39][40][41][42] In the proposed interface constitutive model, the effect of particle breakage in interface area is taken into account by translating downward the CSL in the e-σ n plane through the determination of the reference critical void ratio (e ref ) using the approaches by Liu et al 43 as given in Equation (11). ...
This paper aims to develop the nonlinear incremental modeling approach for describing both monotonic and cyclic behaviors of the soil‐structure interface. An exponential function is adopted as an example to reproduce the asymptotic relationship between the interface shear stress ratio and the shear displacement. A stress‐dilatancy relation is developed for the shear‐induced change of interface thickness. A shear stress reversal technique is incorporated for cyclic loading effect. Then, three numerical schemes for simulating constant thickness, constant normal load, and constant normal stiffness tests are established respectively. Next, three modifications are made to enhance the model by introducing a nonlinear shear modulus, the critical state concept, and the grain breakage effect. The enhanced model is evaluated with satisfactory performance in simulating interface tests under various loading conditions. Furthermore, the extensions to other nonlinear incremental interface model and clay‐structure interface modeling with rate effect relating to drainage conditions are successfully demonstrated and discussed.
