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Analytical and experimental investigation of a disturbed zone around a pipe in sand

  • Ying Ping Xiao
  • Hong Cao
  • Cong Zhai
Technical Paper
  • 75 Downloads

Abstract

Backward erosion piping is an important failure mechanism in both dikes and dams where sandy layers are covered by a cohesive layer. Shallow pipes are formed at the interface of the sandy or silty layer and the cohesive cover layer. As a pipe is formed, a zone of disturbed sand grains forms around it, which may have an effect on the equilibrium of forces on the grains at the tip and walls of the pipe. This study focuses on the size and hydraulic conductivity of the disturbed zone, and its impact on pipe progression. Experiments were conducted with a range of sand types, to investigate the process of disturbed zone formation at the grain scale. A camera was used to record the process of pipe formation from above. Images captured during pipe development were analysed to obtain displacement fields for particles in front of the pipe tip, and to determine the size and degree of looseness of the disturbed zone there. The hydraulic conductivities of the disturbed soils were estimated based on the displacement of sand grains. An algorithm was derived to calculate the hydraulic head distribution in front of the pipe tip, taking the disturbed zone into consideration. Based on this, the effect of the disturbed zone on the hydraulic conditions near the pipe tip was analysed. The findings of the study are essential to properly understanding the backward erosion mechanism.

Keywords

Erosion Piping Laboratory tests Dam Levee 

Notes

Acknowledgements

The financial support provided by The State Key Laboratory of Subtropical Building Science is gratefully acknowledged. The thoughtful comments from anonymous reviewers and the editors are appreciated.

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Copyright information

© The Brazilian Society of Mechanical Sciences and Engineering 2018

Authors and Affiliations

  1. 1.The State Key Laboratory of Subtropical Building ScienceSouth China University of TechnologyGuangzhouChina
  2. 2.School of Transportation and Civil Engineering and ArchitectureFoshan UniversityFoshanChina

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