Examining Atterberg Limits for Expansive Soils
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Date
2006-12
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Addis Ababa University
Abstract
Expansive soils have been responsible for many structural damages that result in great
financial losses in many parts of the world including Ethiopia. Proper understanding of the
properties of the soil helps to understand the actual causes of failure of structure.
The main objective of this research work is to examine Atterberg limits by giving emphasis
on the range at which a reduction of water content will not cause a decrease in the volume of
the soil mass, i.e. shrinkage limit. In addition to this an attempt has been made to define the
maximum moisture content corresponding to the maximum swelling and the effect of initial
moisture content on the swell pressure of expansive soils.
To achieve the research objective, disturbed and undisturbed samples of both Expansive and
red clay soils were collected from Addis Ababa. The red clay soil was used as a methodology
control of Atterberg limits .The following laboratory and field test were conducted to attain
the purpose of this work
Free swell and linear shrinkage
Atterberg limits
Swelling measurement with and without seating load
Artificial flooding of test pit and moisture content
Measuring of volume at various stages of desiccation ( Drying process)
Re wetting of the completely dry pat
Swell pressure measurement by varying initial moisture content
Laboratory test results on both clay samples show that the volume change of expansive soil is
more significant than that of red clay soil. The volume change on expansive soil is mainly due
to the swell property of the soil and this volume change is sufficient enough to develop
distress on structures.
The investigation of swell measurement and moisture content of undisturbed soil samples
showed that the moisture content after a complete swelling is found with in the range of liquid
x
limit and plastic limit. In addition to this high moisture content soils experience less uplift,
but the pressure required to maintain a constant volume is not altered.
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Geo-technical Engineering