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Int J Environ Res Public Health. 2011 Jul;8(7):2640-55. doi: 10.3390/ijerph8072640. Epub 2011 Jun 28.

Geotechnical characterization of mined clay from Appalachian Ohio: challenges and implications for the clay mining industry.

Author information

1
CH2M Hill, 7927 Nemco Way, Suite 120, Brighton, MI 48116, USA. Anthony.Moran@ch2m.com

Abstract

Clayey soil found in coal mines in Appalachian Ohio is often sold to landfills for constructing Recompacted Soil Liners (RSL) in landfills. Since clayey soils possess low hydraulic conductivity, the suitability of mined clay for RSL in Ohio is first assessed by determining its clay content. When soil samples are tested in a laboratory, the same engineering properties are typically expected for the soils originated from the same source, provided that the testing techniques applied are standard, but mined clay from Appalachian Ohio has shown drastic differences in particle size distribution depending on the sampling and/or laboratory processing methods. Sometimes more than a 10 percent decrease in the clay content is observed in the samples collected at the stockpiles, compared to those collected through reverse circulation drilling. This discrepancy poses a challenge to geotechnical engineers who work on the prequalification process of RSL material as it can result in misleading estimates of the hydraulic conductivity of the samples. This paper describes a laboratory investigation conducted on mined clay from Appalachian Ohio to determine how and why the standard sampling and/or processing methods can affect the grain-size distributions. The variation in the clay content was determined to be due to heavy concentrations of shale fragments in the clayey soils. It was also concluded that, in order to obtain reliable grain size distributions from the samples collected at a stockpile of mined clay, the material needs to be processed using a soil grinder. Otherwise, the samples should be collected through drilling.

KEYWORDS:

Appalachian Ohio; Atterberg limits; Recompated Soil Liners (RSL); analysis; clay content; grain size distribution; hydraulic conductivity; hydrometer analysis; mined clay; shale; sieve

PMID:
21845150
PMCID:
PMC3155321
DOI:
10.3390/ijerph8072640
[Indexed for MEDLINE]
Free PMC Article

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