Abstract

As stated in the paper, the term ‘completely weathered’ was used, as recommended by the British Standards Institution (1981), to describe a rock mass in which all the material was decomposed and no visible corestones were present. In this context the term ‘completely’ is etymologically correct.

The terms ‘completely weathered’ used by Moye (1955) and ‘extremely weathered’ used by Stapledon (1976), refer to a material which disintegrates on soaking. The decomposed rock described in the paper did not, as it was well below the water table and already saturated.

Above the water table, factors such as laterization, localized saturation by preferential water paths (sometimes loosely called perched water tables), or desaturation and the development of capillary water tensions, complicate the analysis so much that it would indeed be surprising if correlations between dry density and resistance to penetration were found. In fact, the author wonders if the differences found between the materials classed as EWG and HWG by the writer of the preceding discussion are in any way connected with the weathering process.

The British Standards Institution (1981) does not distinguish between these two classes and recommends using the term ‘decomposed rock’ for both. This is also finding favour with the International Society of Soil Mechanics and Foundation Engineering, who use the greek version ‘saprolite’ (Nogami 1985). It has the advantage that it has been used for decades (Lumb 1962), is recognized by all civil engineers in Hong Kong, and coincides with the term ‘soft ground’ used in excavations and

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