ISSN: 0149-6115
Page Count: 16

Effects of Test Duration and Specimen Length on Diffusion Testing of Unconfined Specimens

Cotten, TE
Geoenvironmental engineer,OR,

Davis, MM
Geotechnical engineer,Shepherd Miller, Inc.,CO,

Shackelford, CD
Associate professor,Colorado State University,CO,

Abstract

Effective diffusion coefficients, D*, of chloride and zinc diffusing in saturated, unconfined specimens of a compacted sandclay mixture are measured for three specimen lengths, L (2.91, 5.83, and 11.60 cm) and three test durations (7, 14, and 21 days). For a specimen length of 2.91 cm, both the chloride and zinc D* values tend to decrease with increasing test duration, possibly due to the measurement of concentration-dependent D* values. For a 14-day test duration, no consistent trend in D* with specimen length is observed, but the overall effect of specimen length on D* is minor relative to the range of measured D* values. A 21-day test duration provides the best correlation between the D* values based on reservoir concentrations, D*^Res, and the D* values based on soil concentrations, D*^Soil, for chloride for a given test regardless of the specimen length. The effect of test duration on the correlation between D*^Res and D*^Soil for zinc is minor based on the relatively narrow range of measured zinc D* values. The observed effects of specimen length on the correlation between D*^Res and D*^Soil for a given test are consistent with the more uniform final porosity distributions in the shorter specimens and the contrasting effects of the non-linear distributions in porosity and dry density that become less significant as the specimen length increases.

Keywords:
adsorption, attapulgite clay, batch equilibrium, chloride diffusion, contaminant transport, diffusion testing, Freundlich isotherm, sand-clay mixture, swelling, zinc diffusion

Paper ID: GTJ10746J
DOI: 10.1520/GTJ10746J
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