ABSTRACT
Unsaturated clays often contain isolated fissures. This study reports laboratory and theoretical investigations on the mechanics of fissure propagation and failure of clay samples subjected to unconfined compression tests. The samples tested had fissures inclined at 15, 30, 45, 60 and 75 degrees with the vertical. They also had water contents (w) of 3, 9, 15, 22 and 27%. The samples with w smaller than 20% were found to behave like brittle materials and their failure was by fissure-induced tension. The samples with w in excess of 20% were found to behave like plastic materials and their failure was in shear. The strength of the samples that failed in tension was found to increase with an increase in w. The strength of the plastic samples was found to decrease with an increase in w. The failure modes of the samples was explained using the pendular, funicular, and saturated water distribution in the samples.
