scholarly journals ANTI-EROSION CAPACITY OF A GRANULAR FILTER SUBJECTED TO A PERIODICALLY VARIABLE HYDRAULIC GRADIENT

2021 ◽  
Vol 55 (4) ◽  
Author(s):  
Yue Liang ◽  
Hongjie Zhang ◽  
Xixi Shi ◽  
Chen Ma ◽  
Bin Zhang ◽  
...  
Keyword(s):  
Water Level ◽  
Hydraulic Gradient ◽  
Internal Erosion ◽  
Cohesionless Soil ◽  
Seepage Velocity ◽  
Seepage Failure ◽  
Granular Filter ◽  
Filter System ◽  
Loading Mode ◽  
Experimental Apparatus

The instability of a filter system is a significant cause of seepage failure in embankment projects. The filter system in the earth-rock embankment is mainly composed of graded cohesionless soil. To uncover the performance of the granular filter in resisting the internal erosion, a set of experiments was carried out with an improved experimental apparatus, considering different hydraulic loading scenarios. The movement of graded cohesionless soil, the seepage velocity and the hydraulic gradient were monitored in the experiments. It was found that during the process of increasing the hydraulic gradient, the failure of the granular filter mainly experienced three stages: the first one was the dynamic equilibrium stage; the second was the critical start stage; and the third was the failure stage, in which a sudden change in the seepage velocity was the precursor of seepage failure. The critical hydraulic gradient and destructive hydraulic gradient decreased with the water level amplitude. Moreover, the experiments revealed that the loading modes of the hydraulic gradient significantly influenced the anti-erosion capacity of the granular filter. Compared with the stepwise loading mode, the cyclic reciprocating loading mode greatly weakened the anti-erosion capacity of the granular filter under the same water level amplitude. The destructive hydraulic gradient of the latter was only 71.8 % of the former under a higher water level amplitude, indicating that the corresponding measures should be considered to avoid the occurrence of a periodically variable hydraulic gradient.

scholarly journals Analysis of Pore Water Pressure and Piping of Hydraulic Well

Water ◽  
2021 ◽  
Vol 13 (4) ◽  
pp. 502
Author(s):  
Jinman Kim ◽  
Heuisoo Han ◽  
Yoonhwa Jin
Keyword(s):  
Numerical Analysis ◽  
Water Level ◽  
Pore Water ◽  
Large Scale ◽  
Pore Water Pressure ◽  
Water Pressure ◽  
Hydraulic Gradient ◽  
Water Levels ◽  
Seepage Velocity ◽  
Seepage Analysis

This paper shows the results of a field appliance study of the hydraulic well method to prevent embankment piping, which is proposed by the Japanese Matsuyama River National Highway Office. The large-scale embankment experiment and seepage analysis were conducted to examine the hydraulic well. The experimental procedure is focused on the pore water pressure. The water levels of the hydraulic well were compared with pore water pressure data, which were used to look over the seepage variations. Two different types of large-scale experiments were conducted according to the installation points of hydraulic wells. The seepage velocity results by the experiment were almost similar to those of the analyses. Further, the pore water pressure oriented from the water level variations in the hydraulic well showed similar patterns between the experiment and numerical analysis; however, deeper from the surface, the larger pore water pressure of the numerical analysis was calculated compared to the experimental values. In addition, the piping effect according to the water level and location of the hydraulic well was quantitatively examined for an embankment having a piping guide part. As a result of applying the hydraulic well to the point where piping occurred, the hydraulic well with a 1.0 m water level reduced the seepage velocity by up to 86%. This is because the difference in the water level between the riverside and the protected side is reduced, and it resulted in reducing the seepage pressure. As a result of the theoretical and numerical hydraulic gradient analysis according to the change in the water level of the hydraulic well, the hydraulic gradient decreased linearly according to the water level of the hydraulic well. From the results according to the location of the hydraulic well, installation of it at the point where piping occurred was found to be the most effective. A hydraulic well is a good device for preventing the piping of an embankment if it is installed at the piping point and the proper water level of the hydraulic well is applied.

Spatial and temporal progression of internal erosion in cohesionless soil

2011 ◽  
Vol 48 (3) ◽  
pp. 399-412 ◽  
Author(s):  
Ricardo Moffat ◽  
R. Jonathan Fannin ◽  
Stephen J. Garner
Keyword(s):  
Seepage Flow ◽  
Hydraulic Gradient ◽  
Internal Erosion ◽  
Cohesionless Soil ◽  
Cohesionless Soils ◽  
Multi Stage ◽  
Internal Instability ◽  
Post Test ◽  
Erosion Test ◽  
Permeameter Tests

Permeameter tests were performed on four widely graded cohesionless soils, to study their susceptibility to internal erosion. Test specimens were reconstituted as a saturated slurry, consolidated, and then subjected to multi-stage seepage flow under increasing hydraulic gradient. The occurrence of internal instability is described qualitatively, from visual observations through the wall of the permeameter during a test and from post-test observations; it is also described quantitatively, from change of hydraulic gradient within the specimen and from axial displacement during a test. The results provide a novel insight into the spatial and temporal progression of seepage-induced internal instability. This insight yields an improved characterization of suffusion and suffosion in cohesionless soils, the progression of which appears governed by a critical combination of hydraulic gradient and effective stress.

scholarly journals Unsteady Seepage Behavior of an Earthfill Dam During Drought-Flood Cycles

Geosciences ◽  
2018 ◽  
Vol 9 (1) ◽  
pp. 17 ◽  
Author(s):  
Ziyang Li ◽  
Wei Ye ◽  
Miroslav Marence ◽  
Jeremy Bricker
Keyword(s):  
Pressure Gradient ◽  
Water Level ◽  
Pore Pressure ◽  
Internal Erosion ◽  
Reservoir Water ◽  
Reservoir Water Level ◽  
Upstream Slope ◽  
Earthfill Dams ◽  
The Stability ◽  
Pore Pressure Gradient

Climate change with extreme hydrological conditions, such as drought and flood, bring new challenges to seepage behavior and the stability of earthfill dams. Taking a drought-stricken earthfill dam of China as an example, the influence of drought-flood cycles on dam seepage behavior is analyzed. This paper includes a clay sample laboratory experiment and an unsteady finite element method seepage simulation of the mentioned dam. Results show that severe drought causes cracks on the surface of the clay soil sample. Long-term drought causes deeper cracks and induces a sharp increase of suction pressure, indicating that the cracks would become channels for rain infiltration into the dam during subsequent rainfall, increasing the potential for internal erosion and decreasing dam stability. Measures to prevent infiltration on the dam slope surface are investigated, for the prevention of deep crack formation during long lasting droughts. Unsteady seepage indicators including instantaneous phreatic lines, equipotential lines and pore pressure gradient in the dam, are calculated and analyzed under two assumed conditions with different reservoir water level fluctuations. Results show that when the water level changes rapidly, the phreatic line is curved and constantly changing. As water level rises, equipotential lines shift upstream, and the pore pressure gradient in the dam’s main body is larger than that of steady seepage. Furthermore, the faster the water level rises, the larger the pore pressure gradient is. This may cause internal erosion. Furthermore, the case of a cracked upstream slope is modelled via an equivalent permeability coefficient, which shows that the pore pressure gradient in the zone beneath the cracks increases by 5.9% at the maximum water level; this could exacerbate internal erosion. In addition, results are in agreement with prior literature that rapid drawdown of the reservoir water level is detrimental to the stability of the upstream slope based on embankment slope stability as calculated by the Simplified Bishop Method. It is concluded that fluctuations of reservoir water level should be strictly controlled during drought-flood cycles; both the drawdown rate and the fill rate must be regulated to avoid the internal erosion of earthfill dams.

scholarly journals Numerical Simulation of the Fluid–Solid Coupling Mechanism of Internal Erosion in Granular Soil

Water ◽  
2020 ◽  
Vol 12 (1) ◽  
pp. 137 ◽  
Author(s):  
Yu Wang ◽  
Junrui Chai ◽  
Zengguang Xu ◽  
Yuan Qin ◽  
Xin Wang
Keyword(s):  
Numerical Model ◽  
Information Exchange ◽  
Stokes Equations ◽  
Exchange Process ◽  
Hydraulic Gradient ◽  
Solid Particles ◽  
Particle Migration ◽  
Internal Erosion ◽  
Particle Flow Code ◽  
Coupling Mechanism

Internal erosion involves migration and loss of soil particles due to seepage. The process of fluid–solid interaction is a complex multiphase, coupled nonlinear dynamic problem. In this study, we used Particle Flow Code (PFC3D, three-dimensional PFC) software to model solid particles, and we applied computational fluid dynamics (CFD) and the coarse mesh element method to solve the local Navier–Stokes equations. An information-exchange process for the PFC3D and CFD calculations was used to achieve fluid–solid coupling. We developed a numerical model for internal erosion of the soil and conducted relevant experiments to verify the usability of the numerical model. The mechanism of internal erosion was observed by analyzing the evolution of model particle migration, contact force, porosity, particle velocity, and mass-loss measurement. Moreover, we provide some ideas for improving the calculation efficiency of the model. This model can be used to predict the initiation hydraulic gradient and skeleton-deformation hydraulic gradient, which can be used for the design of internal erosion control.

A Unified View of Nonlinear Resistance Formulas for Seepage Flow in Coarse Granular Media

Water ◽  
2021 ◽  
Vol 13 (14) ◽  
pp. 1967
Author(s):  
Juan Carlos López ◽  
Miguel Ángel Toledo ◽  
Rafael Moran
Keyword(s):  
Granular Materials ◽  
Granular Media ◽  
State Of The Art ◽  
Seepage Flow ◽  
Hydraulic Gradient ◽  
Nonlinear Relationship ◽  
Seepage Velocity ◽  
Unified View ◽  
Nonlinear Resistance

There are many studies on the nonlinear relationship between seepage velocity and hydraulic gradient in coarse granular materials, using different approaches and variables to define the resistance formula applicable to that type of granular media. On the basis of an analysis of the existing formulations developed in different studies, we propose an approach for comparing the results obtained by some of the most important studies on state-of-the-art seepage flow in coarse granular media.

scholarly journals Study on Critical Hydraulic Gradient Theory of Flow Soil Failure in Cohesive Soil Foundation

Geofluids ◽  
2021 ◽  
Vol 2021 ◽  
pp. 1-13
Author(s):  
Mei Zhou ◽  
Faning Dang ◽  
Yutao Li ◽  
Jiulong Ding ◽  
Jun Gao
Keyword(s):  
Shear Strength ◽  
Cohesive Soil ◽  
Hydraulic Gradient ◽  
Gradient Theory ◽  
Clay Layer ◽  
Soil Thickness ◽  
Seepage Failure ◽  
Critical Hydraulic Gradient ◽  
Comparison Results ◽  
Soil Foundation

The current formula of critical hydraulic gradient is not adapted to solve critical hydraulic gradient of cohesive soil. Assume that the seepage failure mode of the cohesive soil foundation was cylindrical or inverted circular truncated cone, based on the calculation formula of the critical hydraulic gradient of Terzaghi, the analytical formula of the critical hydraulic gradient considering the influence of the shear strength of the soil was derived. Then, the seepage failure process of the clay layer was simulated numerically, and the effects of the clay layer thickness, failure radius, and shear strength indexes on the critical hydraulic slope were analyzed. The comparison results show that the numerical test results are in good agreement with the calculated results of the new formula. In addition, the critical hydraulic gradient of sandy loam and loess under different working conditions was studied severally by a self-made permeation failure instrument. The results show that the critical hydraulic gradient decreases with the increase of soil thickness and failure radius, and the maximum error between the test and the corresponding formula results is no more than 16%.

Three-dimensional analysis of water infiltration into the Gouhou rockfill dam using saturated–unsaturated seepage theory

2006 ◽  
Vol 43 (5) ◽  
pp. 449-461 ◽  
Author(s):  
Qun Chen ◽  
L M Zhang
Keyword(s):  
Three Dimensional ◽  
Water Infiltration ◽  
Internal Erosion ◽  
Seepage Water ◽  
Two Dimensional ◽  
Material Anisotropy ◽  
Seepage Failure ◽  
Rockfill Dam ◽  
Seepage Theory ◽  
Unsaturated Seepage

The Gouhou Dam was a concrete-faced rockfill dam built in a steep canyon that collapsed in 1993 due to internal erosion during the initial reservoir filling. In this paper, the process of water infiltration into the originally unsaturated rockfill dam is studied using three-dimensional saturated–unsaturated seepage theory. The three-dimensional characteristics of seepage through the dam bounded by steep abutments, the effect of material anisotropy, and the effect of rockfill stratifications are studied. The three-dimensional results are compared with those from two-dimensional analyses. The three-dimensional simulations show that seepage water flows faster and the hydraulic gradients are greater near the abutment boundary in the dam. As such, the evolution of the seepage failure in the three-dimensional cases is faster than that in the two-dimensional analyses, and the two-dimensional analyses will underestimate the risk of seepage failure, particularly near the abutment boundary. If the materials in the dam were uniform, the reservoir water would infiltrate into the dam along a downward flow path towards the riverbed, and not exit from the surface on the downstream slope. Increasing the horizontal coefficient of permeability of the rockfill increases the infiltration velocity, but the material anisotropy does not appreciably change the infiltration pattern. Stratifications in the rockfill, however, cause the seepage water to advance more quickly in the horizontal direction along the interface between the sandwich layer and the rockfill, thus increasing the possibility of seepage failure.Key words: seepage, seepage failure, rockfill dam, unsaturated soils, wetting front, numerical analysis.

scholarly journals Effect of Clay on Internal Erosion of Clay-Sand-Gravel Mixture

2020 ◽  
Vol 2020 ◽  
pp. 1-18
Author(s):  
Chen Liang ◽  
Cai Guo-dong ◽  
Gu Jia-hui ◽  
Tan Ye-fei ◽  
Chen Cheng ◽  
...  
Keyword(s):  
Hydraulic Conductivity ◽  
Fine Particle ◽  
Fine Particles ◽  
Fine Sand ◽  
Hydraulic Gradient ◽  
Internal Erosion ◽  
Engineering Project ◽  
Critical Flow Velocity ◽  
Critical Hydraulic Gradient ◽  
Mixture Samples

In this study, a one-dimensional seepage test apparatus was used to investigate the effect of clay on the critical hydraulic gradient, hydraulic conductivity, migration of fine particles in soil, and percentage of fine particle loss during the internal erosion of clay-sand-gravel mixture, compared with clean gravel. The critical hydraulic gradient and fine sand loss percentage of the clay-sand-gravel mixture decreased, and critical flow velocity and the hydraulic conductivity increased. Six clay-sand-gravel mixture samples with different clay contents were used to evaluate the effect of different clay contents on internal erosion. As the percentage of clay mass to fine particle mass increases from 0% to 25%, the critical hydraulic gradient of soil samples decreases by nearly half and the fine sand loss percentage decreases from 13.73% to 3.48%. Overall, clay has a significant effect on the development of internal erosion of clay-sand-gravel mixture. And attention should be paid in engineering project; clay-sand-gravel mixture with a small amount of clay is more likely to be damaged than clean gravel.

Hydraulic Lifting of Manganese Nodules Through a Riser

2004 ◽  
Vol 126 (1) ◽  
pp. 72-77 ◽  
Author(s):  
J. X. Xia ◽  
J. R. Ni ◽  
C. Mendoza
Keyword(s):  
Deep Sea ◽  
Solid Phase ◽  
Laboratory Data ◽  
Manganese Nodule ◽  
Hydraulic Gradient ◽  
Design Tool ◽  
Water Mixture ◽  
Upward Flow ◽  
Manganese Nodules ◽  
Experimental Apparatus

The calculation of the hydraulic gradient due to the upward flow of a large size particles—water mixture in a vertical pipe is a central problem in the design of systems for deep-sea mining of manganese nodules. Here, the problem is investigated experimentally and with a new calculation method. An experimental apparatus that mimics the deep-sea mining system was built to measure the hydraulic gradient due to the mixture upward flow, the settling velocity of a single manganese nodule, and to explore the relationship between the concentration of fluidized manganese nodules and the solid slip velocity. Experimental relations are found. Also, a formula to compute the total hydraulic gradient of the mixture flow under different flow and solid-loading conditions is developed; the formula accounts for the hydraulic gradients produced by the liquid phase, the solid phase, and the inter-particle collisions. The predictions obtained with the derived equation are compared with experimental data readily available and with the newly acquired laboratory data; these predictions agree very well with the empirical data and demonstrate the value of the model as a design tool.

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