Abstract:
This paper presents the results of a centrifuge study in which swell of an expansive clay profile was induced in the
centrifuge. A factor which has previously hindered such research is the time required to induce significant swell
in-flight, within a reasonable time frame. In this study the use of an artificially fissured fabric together with
geotextile layers allowed for a significant magnitude of swell to be achieved within a matter of hours. Measurements
of matric suction and water content throughout testing highlight the potential difficulties associated
with such measurements in a fissured profile. The suction in clay along the interfaces of fissures can be significantly
reduced almost instantaneously with the ingress of water. In contrast, elements closer to the centre of
intact masses may take significantly longer to respond, illustrating the role of the dual processes (and hence dual
scaling laws) of moisture ingress along fissures, followed by diffusion associated with swelling of the clay. A
comparison of the magnitude of swell induced in this centrifuge model with that of conventional oedometer swell
tests indicated gross overpredictions from the oedometer testing. In this comparison, the severe limitation of
oedometer tests reducing a sample to a point of zero suction is emphasised. Finally, it is illustrated how an
understanding of the rate of swell throughout an expansive profile can provide insights into the validity of the
predictions from oedometer swell tests.
