UNDISTURBED SAMPLING OF SATURATED SANDS BY FREEZING

概要

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A method to obtain undisturbed samples of saturated clean sands is presented. In this method a mixture of ethanol and crushed dry ice is circulated through a buried tube to freeze a column of sand which is then pulled out en masse. Laboratory tests and theoretical analyses were conducted to examine factors influencing the quality of the samples with the following results : (1) For sands containing less than 5-percent fines, the expansive strains due to freezing were less than 0.1 percent when the vertical effective stress exceeded about 0.3 kg/cm^2; (2) a sequence of freezing and thawing had negligible effects on the strength and deformation characteristics of sands under drained conditions; (3) radial freezing in the field is not expected to cause significant change in the mean principal stress in the sand; and (4) the exterior part of the frozen column of sand nearly retained the in situ density. It is concluded that the proposed method of sampling is an effective means to obtain high quality undisturbed samples of clean sands below ground water table, with a built-in capability to check the quality of the samples by determining the density distribution in radial direction.
社団法人地盤工学会の論文
1978-09-15