Compaction properties of lateritic soils (The Case of Assossa)
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Date
2008-04
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Addis Ababa University
Abstract
High temperature and moisture fluctuating in tropical areas, enhancing chemical weathering
leads to the formation of lateritic soils when the soil is well-drained. These highly weathered
tropical materials may irreversibly change properties when dried, and even simply
remoulding the material may cause significant change in properties.
Embankment construction is one of the major activities in Civil Engineering works, which
enhance development. Hence, great attention has to be given during construction of such
infrastructures when using the tropical soils as construction materials.
Embankments which are constructed using lateritic soils have a great advantage in that they
are constructed from locally available materials within sound technical and affordable
financial capacity. To use lateritic soils safely and economically, appropriate methods of
determining the geotechnical properties, compaction properties, shear strength parameters,
unconfined compression strength (UCS) have to be investigated and developed.
Accordingly, in this paper the compaction properties of lateritic soils which are taken from
Assossa have been investigated. In addition to this, some peculiar geotechnical and geochemical
characteristics of these soils have been studied. Accordingly, the soils from Assossa
have been obtained to be true lateritic as the geo-chemical test and tests from laboratory
indicated.
The soil samples were compacted at optimum moisture content, at drier side of the optimum
moisture content and at wetter side of the optimum moisture contents. Then, the UCS tests
were done on the soil samples to investigate the variation in strength properties as a function
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of time after compaction of these soils. Keeping the compacted lateritic soil samples for a
longer period shows an increase in the UCS values and samples compacted at optimum
moisture content have higher values of UCS as compared to the once on the drier and wetter
sides.
Compaction of these soils has been influenced by depth, drying, mineralogical composition
and compaction energy as illustrated in this thesis. Moreover, the effect is higher as the
degree of laterization increases.
The effect of permeability of compacted lateritic soils in relation to change in compaction
moisture content and time effect after compaction were investigated.Acordingly, the effect of
compaction moisture shows that permeability decreases towards the optimum moisture
content. In addition to this, the time effect after compaction has been investigated and the test
showed that permeability decreases as time after compaction increases.
The soils are less sensitive to expansion when there is fluctuation of water. Further, the soil is
highly sensitive to remoulding of samples as the compaction curves and the degree of
sensitivity showed.
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Case of Assossa