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Cohesion in colloidal soils

Published online by Cambridge University Press:  27 March 2009

F. Hardy
Affiliation:
(Imperial College of Tropical Agriculture, Trinidad, British West Indies.)

Extract

1. Experiments in which were measured the resistances to (a) transverse breaking, (b) crushing, and (c) parting under tensile pull of standard blocks of soil prepared in different ways and under particular moisture conditions are described and discussed.

2. The soils examined comprised three highly colloidal siliceous soils containing amounts of calcium carbonate ranging from 7·2 to 0·2 percent., and two red lateritic soils.

3. The most significant results were obtained by employing, in a special tenacity apparatus, granular test-blocks, prepared by moistening sieve-graded dry soil packed into rectangular moulds. The results thus obtained are believed to furnish a reliable measure of the cohesiveness of soil colloidal matter, especially in soil blocks that have previously been brought to constant moisture content in a humidifier. The method of preparation simulates the effect of rain in causing the “running together” of colloidal soil particles.

4. The relative cohesiveness of the soils examined appears to follow the same order as their rates of settling from aqueous suspension. This observation strengthens the view that cohesiveness in colloidal soils is to a certain extent due to chemical forces that depend on the presence of active atoms or atomic groups possessing powerful fields of residual affinity, although probably film tension also plays a part.

Type
Research Article
Copyright
Copyright © Cambridge University Press 1925

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References

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page 423 notes 1 Manufactured by Central Scientific Company, U.S.A.

page 424 notes 1 Unless the granular soil blocks are prepared by adding water slowly to the sifted soil, swelling causes them to assume a convex upper surface, so that their cross-sectional area exceeds 1 sq. in.

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page 427 notes 2 Hardy F., J. Agric. Sci., loc. cit., also Journ. Phys. Chem. (in press).

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page 429 note 2 The flocculation phenomena of the lateritic soils employed in these investigations are fully described in the article already cited (footnote 1). The siliceous soils behaved normally in that the rate of flocculation of their aqueous suspensions varied directly with lime content. The highly calcareous soil settled from suspension rather more slowly than either of the lateritic soils.

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