Short-Term Hydraulic Conductivity and Consolidation Properties of Soil-Bentonite Backfills Exposed to CCR-Impacted Groundwater

AbstractThe present study investigated the effectiveness of two soil-bentonite slurry wall backfills, specifically sand/conventional Na-bentonite (NaB) and sand/hexametaphosphate (SHMP)-amended Ca-bentonite (SHMP-CaB), for the containment of the coal combustion residuals (CCR) impacted groundwater....

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Bibliographic Details
Published in:Journal of geotechnical and geoenvironmental engineering 2018-06, Vol.144 (6)
Main Authors: Yang, Y.-L, Reddy, Krishna R, Du, Y.-J, Fan, R.-D
Format: Article
Language:English
Subjects:
Backfill
Bentonite
Chemical compatibility
Compressibility
Compression
Conductivity
Consolidation
Containment
Distilled water
Drinking water
Duration
Groundwater
Hydraulic conductivity
Hydraulics
Liquid limits
Sand
Scanning electron microscopy
Short term
Slurries
Soil
Soil compressibility
Soil investigations
Soil properties
Swell
Technical Papers
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Summary:AbstractThe present study investigated the effectiveness of two soil-bentonite slurry wall backfills, specifically sand/conventional Na-bentonite (NaB) and sand/hexametaphosphate (SHMP)-amended Ca-bentonite (SHMP-CaB), for the containment of the coal combustion residuals (CCR) impacted groundwater. Several series of laboratory experiments were conducted to determine swell index, liquid limit, slump, hydraulic conductivity, and compressibility of the backfills using distilled water or tap water and simulated CCR impacted groundwater. The results showed that NaB exhibited a higher free swell index as compared with that of SHMP-CaB in both the CCR-impacted groundwater and the distilled water. Both NaB and SHMP-CaB possessed lower liquid limit values with the CCR-impacted groundwater. During the test duration of 96 days, the CCR-impacted groundwater caused 1.39 times increase in the short-term hydraulic conductivity of the sand/NaB backfill, while there was a 0.95–0.91 times decrease in the short-term hydraulic conductivity of the sand/SHMP-CaB backfill. The compression index and rebound index values of the tested backfills prepared with the CCR-impacted groundwater were lower than the backfills prepared with tap water. Scanning electron microscope analysis showed that SHMP promoted the Ca-bentonite to exist in more dispersed particle association with smaller particle size, resulting in the observed results for SHMP-CaB backfill. Additional research is recommended to assess long-term chemical compatibility of the backfills with CCR-impacted groundwater.
ISSN:1090-0241
1943-5606
DOI:10.1061/(ASCE)GT.1943-5606.0001877