Soil bentonite (SB) slurry trench cutoff walls have been widely used for over 40 years to control ground water flow through and beneath dams and levees and to control subsurface contaminant transport at contaminated sites. The idea that the state-of-stress in SB slurry trench cutoff walls is less than geostatic was first published over 30 years ago and it is well established that the hydraulic conductivity of SB backfill is stress dependent. With funding from the National Science Foundation, a full-scale, instrumented SB slurry trench cutoff wall was constructed with embedded instrumentation that directly measures the stress and pore pressure in three dimensions at multiple depths and locations. These data have been synthesized and the authors compare the results of stress measurements in this wall with various models. Finally, the authors provide summary opinions and practical recommendations for the design and construction of SB walls.
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