Long-Term Risk Assessment of Levee Cutoff Walls-PPT Presentation

PPT Presentation

Pdf Summary

The presentation assesses long-term risks to seepage cutoff walls in levees, which are widely used to control seepage but lack established methods for monitoring their condition over decades. Because wall longevity and functionality are uncertain, aging infrastructure creates uncertainty in levee risk assessments, maintenance costs, and community safety.<br /><br />Potential deterioration mechanisms include seismic damage, cracking from drying, chemical reactions that degrade cement or bentonite, vegetation and root intrusion, and animal burrows. Possible consequences include increased permeability and through-seepage, piping, slope instability, and leakage at joints, gaps, or wall edges. Interviews with USACE experts found that walls are typically judged through surface inspections; seepage is often attributed to underseepage, while instrumentation may receive limited monitoring after construction. Experts generally reported few observed wall failures, but acknowledged gaps in knowledge.<br /><br />A seepage simulation showed that a cutoff wall can substantially reduce exit gradients while its hydraulic conductivity remains low; performance diminished as conductivity increased. The presentation concludes that cutoff walls are generally durable and effective, but recommends greater monitoring and investigation in high-risk or high-consequence areas. Proposed future work includes recording wall attributes in national infrastructure databases, modeling damaged-wall performance, and coring older walls to assess changes in permeability.

Keywords

seepage cutoff walls

levees

long-term durability

monitoring

deterioration mechanisms

permeability

underseepage

piping

USACE experts

infrastructure risk