Volume Change Characteristics of Unsaturated Clay

Compression tests under controlled effective stress paths show the stress path independence of volumetric strain and degree of saturation. Stress path dependency appears to be caused by a reversal in the direction of saturation. The swelling process does not in itself appear to introduce an important path dependency. The collapse mechanism is controlled by a potentially unstable structure, a high applied stress and a high suction pressure. The absence of one of these three factors removes the possibility of significant collapse. The effect of molding water content and compaction method on the structure of compacted clay is illustrated by the different compression behavior of clays compacted dry and wet of optimum. The compression behavior is treated best in terms of the separate components of applied stress and suction pressure, and for one-dimensional compression, the stress-strain relationship for a clay can be stated in a simple form.