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Geotechnical properties and behaviour of the Monasavu halloysite clay, Fiji

Published online by Cambridge University Press:  09 July 2018

D. J. Knight
D. J. Knight*
Affiliation:
Geotechnical Engineering, Sir Alexander Gibb & Partners, Earley House, London Road, Earley, Reading RG6 1BL
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Abstract

Geotechnical properties and behaviour are described of the very wet, halloysitic, residual clay found in the dense rain forest at Monasavu, Viti Levu, Fiji, where the annual rainfall can exceed 5 m. The tropical climatic conditions have caused deep weathering of sandstones and produced a highly plastic clay with low density and a natural moisture content greatly in excess of the standard compaction optimum. This clay was found to contain halloysite which was ‘amorphous’ rather than crystalline. The material was used in this natural state in an 85-m high rockfill dam at Monasavu Falls as an unusually soft core, the construction of which involved unconventionally light compaction by low-ground-pressure-tracked dozers. Its resulting behaviour in terms of three-dimensional total and effective stresses, stress paths and deformations throughout the construction, impounding and full reservoir stages was closely monitored. This behaviour is examined in the light of the clay's classification, mineralogical, compaction and engineering properties determined before and during construction. Despite its unusual properties, it is concluded that the clay is a good engineering material, behaving like others containing halloysite in the more common tubular form, and, moreover, that the high natural moisture content is of positive benefit.

Type
Research Article
Information
Clay Minerals , Volume 21 , Issue 3 , September 1986 , pp. 311 - 332
Copyright
Copyright © The Mineralogical Society of Great Britain and Ireland 1986

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