Seepage through and under existing levees and embankment dams is a major threat tosuch structures all across the country, and programs of unprecedented scale have beeninitiated to remediate this problem. In other publications, the authors have describedmethods used to create cut-offs for dams, hundreds of feet deep through overburden, filland rock (principally karstic limestone and dolomite). However, much work is projectedor is actually underway to considerably shallower depths in Sacramento, New Orleansand Lake Okeechobee, as examples. The paper provides a technology review of thevarious methods used to install such cut-offs, principally in softer ground conditions.These technologies include:· Category 1cut-offs involve backfilling of a trench previously excavated underbentonite slurry. Examples include the use of backhoes, grabs and hydromills.· Category 2cut-offs involve the mixing of the levee and foundation soils in situ.Examples include conventional (vertical axis) Deep Mixing, the TRD method andCSM method.For each, the pros and cons, methodologies, applicability and budget costs are provided,as are details from recent case histories and a comprehensive bibliography.
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