An investigation into Atterberg limits and their suitability for assessing the shrinkage and swelling characteristics of clay soils for foundation design.
Matthew Frost
C. A. Gray
2134/3592
https://repository.lboro.ac.uk/articles/online_resource/An_investigation_into_Atterberg_limits_and_their_suitability_for_assessing_the_shrinkage_and_swelling_characteristics_of_clay_soils_for_foundation_design_/9438245
Clay soils shrink and swell with changes in moisture content. This can be
exacerbated in the presence of trees, and in the vicinity of buildings, the resultant
effects can cause structural damage. For foundation design in such circumstances in
the UK, reference is often made to guidelines published by the National House
Building Council (NHBC), which were primarily written for low-rise residential
structures. These guidelines are based on a clay shrink / swell potential assessed
using Atterberg Limits and a 'water demand' classification for trees.
Atterberg limits are semi-empirical tests that assess a fraction of a soil sample which
passes an arbitrary sieve size. The structural features of clay soils, mineralogy,
chemistry, prior stress history and cyclic effects all influence the magnitude of
volumetric change. Atterberg limits do not directly measure any of these features but
have been related to some of them empirically.
This paper reviews the processes of clay shrinkage and swelling and the applicability
of the Atterberg limits in the assessment of volume change potential. It concludes
that modifications to the NHBC guidelines can make designs more site specific.
However, because the guidelines are based on a cost - benefit analysis, they will
over-design foundations for structures other than low rise residential houses and will
not be relevant for others. It is concluded that a more appropriate analysis should be
based on a wider overall assessment of all the available soil/site information, in
conjunction with a simple assessment of plasticity.
2008-09-01 14:58:04
Atterberg limits
Clay shrinkage
Foundation design
NHBC 4.2
Volumetric change
Tree root damage
Built Environment and Design not elsewhere classified