INTERPRETING THE "COLLAPSING" BEHAVIOR OF UNSATURATED SOIL BY EFFECTIVE STRESS PRINCIPLE

This paper examines the applicability of suction stress-based effective stress in describing the "collapsing" behavior of soil in oedometer testing under inundation conditions. The experimental data, originally used to invalidate Bishop's effective stress in the earlier sixties, are used to illustrate that the suction stress-based effective stress can well reconcile the phenomenon of soil sample "collapsing" during inundation process. It is shown that during inundation, suction stress increases drastically, leading to drastic reduction in effective stress and the failure of soil sample in oedometer without any changes in total stress.