Abstract:
The geotechnical investigation of most sites located on dolomite
invariably includes the assessment of the nature and properties of the
residual weathering product of the dolomite, termed "wad". Ironically,
much confusion previals concerning the geotechnical properties of this
material leading to its potential behaviour often being grossly misinterpreted.
This study attempts to improve the understanding of this comp~ex
material, its origin, structure and geotechnical properties.
Two principal types of weathering product of dolomite rock have been
identified namely wad and ferroan soils. These respective groups of
materials may be subdivided into laminated or ~assive wad and laminated
or massive ferroan soil on the basis of the ma~r?fabric they display.
Secondary features, such as bedding planes and joints superimposed on the
original parent rock may be retained as residual features.
The disturbance, displacement, slumping and reworking of the residual massive and laminated wad and ferroan soils, with the possible addition
of external impurities, give rise to a material which may be classed as a
totally reworked wad or ferroan soil.
The geotechnical properties of.the different wad and ferroan spils have
been ascertained through laboratory and field testing. Relationships
between the nature, form and spatial arrangement of macrofabric features
and laboratory measurements have been examined. The influence of secondary
features or discontinuities imposed on these soils, are considered.
Wad and ferroan soils are noted to possess both poor and very positive
behavioural characteristics. The assessment of these materials, requires
that particular attention is paid to fabric description and degree of
reworking. Several additions to the MCCSSO system of soil profile
description are proposed to embrace discriptors essential for the
engineering geological appreciation of a site underlain by wad and/or
ferroan soil.
