Moisture conditions associated with pavements in South Africa
Date
2015-01-26
Authors
Haupt, Frank Johannes
Journal Title
Journal ISSN
Volume Title
Publisher
Abstract
A variety of geotechnical and pavement engineering problems require that
one know whit the eventual moisture conditions under a covered area will
be, as considerable savings may result from preventive design measures.
The historical development of the theory describing soil water movement
is summarized and the factors affecting the establishment of the moisture
regime in pavements are discussed. & comprehensive literature survey,
firstly to determine the state of the knowledge concerning pavement
moisture conditions and secondly to accumulate the greater part of
available moisture prediction techniques, was carried out and the salient
features are highlighted. It was decided to evaluate these models'
prediction accuracies when applied to local conditions and for this all
available local moisture information was gathered. The most common methods
available to measure soil water potential are briefly discussed and
recommendations regarding routine measurements put forward. None of the
models tested were found to be applicable without modifications and
consequently an exhaustive statistical analysis of the local data was
undertaken in order to develop more accurate empirical prediction techniques
for local conditions. This analysis included multiple stepwise linear
regressions, the transformation and combination of certain predictors,
linear regressions for certain ranges of values, non-linear regressions
and linear regressions on only selected parameters. Conclusions about
general moisture trends have also been drawn. The influence of climate
and compactive effort on the empirical prediction models were evaluated
and recommendations put forward as to how these influences may be accounted
for in design. A method is proposed for calculating a probable maximum
(or minimum) moisture content for design purposes. The term "characteristic
maximum (or minimum) moisture content" is defined as that moisture content
above (or below) which only a certain percentage of actual moisture content
values will fall. The application of this concept in pavement and geotechnical
engineering is explained. Relationships between other soil
engineering parameters are also given. A provisional rational method,
incorporating soil suction, is also proposed for completeness1 sake. This
method is intended, at least initially, to serve as a check on the empirical
method, but with time it is bound to be refined to a more accurate