Abstract:
The behaviour of collapsible soil is often quantified by conducting a Collapse Potential Test or
double oedometer test. However, these tests interpret the soil behaviour in terms of total stress,
while it is well known that the behaviour of soil is governed by its effective stress. This article
shows the results of a test conducted on undisturbed residual granite to study the collapse of
the soil in terms of effective stress. The test was conducted in a modified oedometer which
allowed the incremental addition of water to the sample during the test. The matric suction was
quantified as a function of the moisture content of the soil during the test. The results indicate
that the reduction in effective stress plays an important role during soil collapse. In addition
it was found that much of the collapse settlement may be due to creep which occurs after the
reduction in effective stress.
