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The behaviour of granular materials when subjected to rotation of their principal axes of stress or strain is not fully understood. In the late 1980s a new apparatus was developed to allow general plane strain conditions to be applied to an analogue soil (Schneebeli cylinders). This paper presents a short description of this apparatus and its capabilities. Experimental results from different types of cyclic tests involving the continuous rotation of principal axes are given, mainly in terms of volume change and the co-axiality of stress and strain increment tensors. The results show that cyclic rotation induces a general tendency to compaction, and that the principal axes of stress and strain increment are not coincident as it is generally assumed in isotropic elastoplastic modelling.

A technique of cementing porous materials artificially using calcite is presented. The technique depends on flushing a mixture of chemical solutions through a porous medium, leading to precipitation of calcite due to reaction of the solution ingredients. The experimental procedures adopted to achieve the cementation are described. The response of different soils to the cementation process is analysed. The bond mechanism created by the calcite is illustrated, using optical and electron micrographs. The paper discusses the factors that appear to determine the response of geomaterials to calcite treatment. It has been found that the strength of a calcite-treated material increases with: (a) intrinsic strength of the individual grains, (b) density, (c) decreasing particle size of the host grains, (d) pre-coating of grains with calcite, and (e) roundness and non-angularity of soil grains. The cementation technique described in this paper has proved successful in reproducing the mechanical behaviour of natural calcarenite from the North West Shelf of Australia.