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<p>Backward erosion piping (BEP), a critical mechanism of internal erosion in levees and dams, initiates at downstream blanket defects where hydraulic pressures exceed the resistance of cohesive soil layers. While prior studies focused on BEP with preset exits, this research investigates failure patterns under varying defect geometries and soil properties through laboratory experiments and a simplified analytical model. The model integrates defect dimensions (length, width, thickness), soil cohesion, and internal friction angle to predict three failure modes: shear, bending, and bending-shear. The model was verified by laboratory results and revealed the following: (1) the increase in soil cohesion and internal friction angle enhanced seepage resistance, but this effect diminished for defects with high length-to-thickness ratios (<i>a</i>/<i>t</i>) or width-to-thickness ratios (<i>b</i>/<i>t</i>); (2) Larger <i>a</i>/<i>t</i> or <i>b</i>/<i>t</i> ratios reduced the shear strength coefficient (<i>η</i>) exponentially, shifting failure dominance from shear to bending; and (3) the combinations of the ratio of the pressure head at the near-upstream edge and far-upstream edge to the head of the reference point (<i>ξ</i><sub>1</sub> and <i>ξ</i><sub>2</sub>) had minimal influence on failure thresholds, but transient flow conditions (e.g., sudden head surges) could bypass gradual bending deformation, triggering abrupt shear failure.</p>

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Analyses for failure patterns of blanket defects on initiation of backward erosion piping

  • 期刊论文

  • 发表日期：

    2025年4月10日

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  • Sige Peng,
  • Chufei Li,
  • John D. Rice,
  • Wu Zhang,
  • Guanyong Luo,
  • Hong Cao,
  • Hong Pan

摘要

Backward erosion piping (BEP), a critical mechanism of internal erosion in levees and dams, initiates at downstream blanket defects where hydraulic pressures exceed the resistance of cohesive soil layers. While prior studies focused on BEP with preset exits, this research investigates failure patterns under varying defect geometries and soil properties through laboratory experiments and a simplified analytical model. The model integrates defect dimensions (length, width, thickness), soil cohesion, and internal friction angle to predict three failure modes: shear, bending, and bending-shear. The model was verified by laboratory results and revealed the following: (1) the increase in soil cohesion and internal friction angle enhanced seepage resistance, but this effect diminished for defects with high length-to-thickness ratios (a/t) or width-to-thickness ratios (b/t); (2) Larger a/t or b/t ratios reduced the shear strength coefficient (η) exponentially, shifting failure dominance from shear to bending; and (3) the combinations of the ratio of the pressure head at the near-upstream edge and far-upstream edge to the head of the reference point (ξ1 and ξ2) had minimal influence on failure thresholds, but transient flow conditions (e.g., sudden head surges) could bypass gradual bending deformation, triggering abrupt shear failure.