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Frontiers of Structural and Civil Engineering

Front. Struct. Civ. Eng.    2014, Vol. 8 Issue (2) : 160-166     https://doi.org/10.1007/s11709-014-0257-7
RESEARCH ARTICLE |
3D finite element method (FEM) simulation of groundwater flow during backward erosion piping
Kristine VANDENBOER1,*(),Vera van BEEK2,3,Adam BEZUIJEN1,2
1. Department of civil Ergineering, Ghent University, Ghent 9000, Belgium
2. Deltares, Delft 2628, Netherlands
3. Section Geoengineering, Delft University of Technology, Delft 2628, Netherlands
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Abstract

Backward erosion piping is an important failure mechanism for cohesive water retaining structures which are founded on a sandy aquifer. At present, the prediction models for safety assessment are often based on 2D assumptions. In this work, a 3D numerical approach of the groundwater flow leading to the erosion mechanism of backward erosion piping is presented and discussed. Comparison of the 2D and 3D numerical results explicitly demonstrates the inherent 3D nature of the piping phenomenon. In addition, the influence of the seepage length is investigated and discussed for both piping initiation and piping progression. The results clearly indicate the superiority of the presented 3D numerical model compared to the established 2D approach. Moreover, the 3D numerical results enable a better understanding of the complex physical mechanism involved in backward erosion piping and thus can lead to a significant improvement in the safety assessment of water retaining structures.

Keywords backward erosion piping      groundwater flow      3D finite element method (FEM)     
Corresponding Authors: Kristine VANDENBOER   
Issue Date: 19 May 2014
 Cite this article:   
Kristine VANDENBOER,Vera van BEEK,Adam BEZUIJEN. 3D finite element method (FEM) simulation of groundwater flow during backward erosion piping[J]. Front. Struct. Civ. Eng., 2014, 8(2): 160-166.
 URL:  
http://journal.hep.com.cn/fsce/EN/10.1007/s11709-014-0257-7
http://journal.hep.com.cn/fsce/EN/Y2014/V8/I2/160
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Kristine VANDENBOER
Vera van BEEK
Adam BEZUIJEN
Fig.1  Schematic drawing of (a) the 2D assumption and (b) its 3D equivalent: A ditch
Fig.2  Contour plot of the flow velocity computed with the 2D FEM model
Fig.3  Vertical exit velocity in the hole
Fig.4  Model geometry
Fig.5  Contour plots of the flow velocity for a hole type exit in different sections
Fig.6  Schematic drawing of the flow patterns for a ditch (a), a hole (b), a hole with a growing pipe (c) and a hole after breaching of the pipe (d)
Fig.7  Vertical exit velocity in the outflow opening for different widths W (a) and vertical exit velocity as a function of the model width (b)
Fig.8  Top view contour plot, flow and vertical outflow velocity in the center of the hole for a single outflow opening (a) and three outflow openings (b) with model width 30 cm
stageH/cmflow/(mL·min-1)pipe volume/mm3pipe length/mmlargest pipe width/mmpipe depth/mm
121.60000
2639.142834102.5
38.565.78696510.62.5
48.568.111281008.22.7
58.571.316821408.82.7
69115.6757934016.42.7
79164.82955134064.42.7
Tab.1  Pipe characteristics, gradient and flow for 7 pipe development stages
Fig.9  Photo of the pipe and crater at a certain moment during the experiment
Fig.10  Flow as a function of pipe volume: Comparison between numerical results and experimental measurements
Fig.11  Evolution of the maximum exit velocity as a function of the model width for the different pipe development stages. The stages refer to Table 1
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