Apparatus for Constant Rate-of-Strain Consolidation of Slurry Mixed Soils

A constant rate-of-strain (CRS) consolidation apparatus was developed to allow testing of slurry mixed soils prepared within 102-mm (4-in) inner diameter acrylic columns with varying lengths using a laboratory mixing apparatus. The laboratory mixing apparatus was previously developed to mimic the mixing process associated with the use of slurries containing bentonite and granular zero-valent iron (ZVI) for in situ remediation at sites contaminated with chlorinated solvents. Example consolidation results are provided for specimens of dry sand mixed with bentonite-ZVI slurry with lengths of 305 mm (12 in), 457 mm (18 in), or 610 mm (24 in). After mixing, all of the specimens except for the 610-mm specimen were consolidated directly within the same columns to minimize sampling disturbance. The 610-mm specimen was sectioned into thirds before consolidation testing to evaluate effects of vertical heterogeneity. As expected, all specimens were highly compressible, with maximum (large) strains ranging from 10.7 % to 48.0 %. For specimens prepared and tested within the same columns, the effects of differences in column length and strain rate were minor. The CRS testing apparatus offered a convenient, rapid (< 3 day), and economical approach for evaluating the consolidation behavior of the bentonite-ZVI slurry mixed sand.