BASTOS, E. G.; BASTOS, Edinalva Gomes.
Abstract:
The mechanism of volume change on expansive clays is influenced by a number of
factors, which can be considered in three groups: the soil properties, the environmental
conditions and the state of stress. The main purpose of this thesis is to present the volume
change behavior of an unsaturated expansive clay from the north coast of Pernambuco. The
experimental research carried out involved soil characterization, soil suction and soil moisture
content profiles up to 4.5 m. These profiles were used to determine the depth of active layer.
In situ soil suction is measured by employing the filter paper method. For extreme climate
conditions the soil suction varies from 40 kPa to 6.000 kPa at 1.0 m depth. Volume changes
behavior was investigated using oedometer tests under controlled vertical stress and suction.
The potential swell and swell pressure parameters were also determined using the standard
oedometer tests. Membrane pressure cells were used in the determination of suction-moisture
content relationships. These studies were used to predict volume changes using three simple
methods based on laboratory and field tests data. Shrink/swell prediction results are shown
to be a reasonable agreement with the observations. In general, the predicted results tends to
overestimate field shrink/swell. With reference to volume change, the soil suction parameter
allows a best ability to represent unsaturated soils.
