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Piping in loose sands: the importance of geometrical fixity of grains

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Abstract
Piping is one of the possible failure mechanism for dams and levees with a sandy foundation. Water flowing through the foundation causes the onset of grain transport, due to which shallow pipes are formed at the interface of the sandy layer and an impermeable blanket layer. In the past, the mechanism has been investigated predominantly in densely packed sands, in which the process was observed to start at the downstream side (backward erosion). Recently performed experiments in loose sand (van Beek et al. 2009) showed a different failure mechanism (forward erosion). In this article additional experiments of piping in loose sands are described for investigating the relevance of the forward process for practice. In these experiments the type of process was found to be dependent on the presence of shear resistance between sand box cover and top sand grains, that causes grains to be fixed geometrically. Without this shear resistance the process was found to be forward, whereas with this shear resistance the process was found to be backward oriented. The change in degree of fixity and relative density as a result of loading is investigated with electrical density measurements. The experiments show that the forward process is not relevant for levees in practice, in which the cohesive blanket layer causes the sand grains to be fixed properly.
Keywords
backward erosion, electrical density, forward erosion, piping, relative density

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Chicago
Van Beek, Vera, Adam Bezuijen, and FM Schenkeveld. 2012. “Piping in Loose Sands: The Importance of Geometrical Fixity of Grains.” In 2nd European Conference on Physical Modelling in Geotechnics, Proceedings, 1–10. Ghent, Belgium: Ghent University, Department of Civil engineering.
APA
Van Beek, Vera, Bezuijen, A., & Schenkeveld, F. (2012). Piping in loose sands: the importance of geometrical fixity of grains. 2nd European conference on physical modelling in geotechnics, Proceedings (pp. 1–10). Presented at the 2nd European conference on physical modelling in geotechnics (EUROFUGE - 2012), Ghent, Belgium: Ghent University, Department of Civil engineering.
Vancouver
1.
Van Beek V, Bezuijen A, Schenkeveld F. Piping in loose sands: the importance of geometrical fixity of grains. 2nd European conference on physical modelling in geotechnics, Proceedings. Ghent, Belgium: Ghent University, Department of Civil engineering; 2012. p. 1–10.
MLA
Van Beek, Vera, Adam Bezuijen, and FM Schenkeveld. “Piping in Loose Sands: The Importance of Geometrical Fixity of Grains.” 2nd European Conference on Physical Modelling in Geotechnics, Proceedings. Ghent, Belgium: Ghent University, Department of Civil engineering, 2012. 1–10. Print.
@inproceedings{2097875,
  abstract     = {Piping is one of the possible failure mechanism for dams and levees with a sandy foundation. Water flowing through the foundation causes the onset of grain transport, due to which shallow pipes are formed at the interface of the sandy layer and an impermeable blanket layer. In the past, the mechanism has been investigated predominantly in densely packed sands, in which the process was observed to start at the downstream side (backward erosion). Recently performed experiments in loose sand (van Beek et al. 2009) showed a different failure mechanism (forward erosion). In this article additional experiments of piping in loose sands are described for investigating the relevance of the forward process for practice. In these experiments the type of process was found to be dependent on the presence of shear resistance between sand box cover and top sand grains, that causes grains to be fixed geometrically. Without this shear resistance the process was found to be forward, whereas with this shear resistance the process was found to be backward oriented. The change in degree of fixity and relative density as a result of loading is investigated with electrical density measurements. The  experiments show that the forward process is not relevant for levees in practice, in which the cohesive blanket layer causes the sand grains to be fixed properly.},
  author       = {Van Beek, Vera and Bezuijen, Adam and Schenkeveld, FM},
  booktitle    = {2nd European conference on physical modelling in geotechnics, Proceedings},
  keyword      = {backward erosion,electrical density,forward erosion,piping,relative density},
  language     = {eng},
  location     = {Delft, The Netherlands},
  pages        = {1--10},
  publisher    = {Ghent University, Department of Civil engineering},
  title        = {Piping in loose sands: the importance of geometrical fixity of grains},
  year         = {2012},
}