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The paper describes the development of a method for the compaction of groups of identical oedometer specimens. Groups were compacted from several soils at various densities and moisture contents. The specimens in each group were tested later in the oedometer over the complete range of initial saturations, and it was important that they should be as near as possible to identical after compaction.
The paper considers, by means of a literature review, the various methods of compaction available. The conclusion reached is that the static method is most suitable for compaction of relatively thin specimens. Soil was compacted directly into the oedometer rings under static loading. The advantages and disadvantages of this approach are discussed.
A special mold developed for this purpose is described in detail. This enabled a known mass of soil to be compacted into a 76.2 by 19.05-mm-thick specimen. The procedure used in the laboratory is outlined.
It was necessary to allow most specimens to either increase or decrease in moisture content after compaction so that oedometer tests could be carried out over the complete range of saturation. The procedures followed are described, and it is stressed that these model as closely as possible what would happen in a road embankment.
Finally, the paper considers the dry densities of groups of specimens immediately prior to being placed in the oedometer. It is shown that variations within each group are lower than those found in undisturbed samples, and it is concluded that the standardized method produced groups of specimens which were closer to identical than would have been obtained by other methods. This, in turn, enabled the influence of other variables, principally the compaction moisture content and initial dry density, to be studied with more confidence.
soils, compaction, embankments, collapse settlement, consolidation, oedometers, density, partial saturation, roads
chief research officersenior engineer, National Institute for Road ResearchDuff and Geddes, PretoriaEdinburgh,