Cut-off Wall for “Old” Dams for Restricting/Preventing Leakages/Seepages-PPT Presentation

PPT Presentation

Pdf Summary

The presentation describes cut-off walls (COWs) as a method for reducing or preventing seepage through aging dams and embankments. It outlines installation using trench cutters or Cutter Soil Mixing (CSM), including one- and two-phase procedures. Quality control includes wet-grab sampling and coring, with typical performance requirements of 28-day unconfined strength around 0.75–4 MPa and permeability near 10⁻⁸ m/s.

Four projects illustrate the technology’s range:

- <strong>Lake Okeechobee, Florida (2008–2014):</strong> A CSM wall addressed uncontrolled water loss and stability concerns at the Herbert Hoover Dike. Soil was predrilled where necessary, then mixed with cement-based slurry.
- <strong>Rennersdorf, Germany (2013–2014):</strong> A 6.5-km-long wall, up to 30 m deep, rehabilitated a flood-retention dam with seepage through its bitumen-core sealing. The two-phase CSM method used overlapping primary and secondary panels, with a minimum 5 m embedment.
- <strong>Dead Sea, Israel (2011–2014):</strong> A 34.2 m-deep, 800 mm-wide wall was installed in abrasive gravel, clay, limestone, and saline groundwater. The project used specialized materials and equipment, with sheet piles incorporated into the wall.
- <strong>Red Dog Mine, Alaska (2007–2010):</strong> A wall up to 45 m deep limited seepage from a tailings impoundment. Excavation passed through warm permafrost, variable overburden, and fractured bedrock, and the wall was keyed at least 0.9 m into low-permeability rock. Panels were excavated under slurry and backfilled with tremie-placed plastic concrete.

Together, the cases demonstrate how cut-off-wall design and construction can be adapted to different dam conditions, geology, climates, and seepage-control requirements.

Keywords

cut-off walls

seepage control

dam rehabilitation

embankment dams

Cutter Soil Mixing

trench cutter

quality control

permeability

unconfined strength

tailings impoundment