Some aspects of the compression and collapse behaviour of an unsaturated natural loess

The compression and collapse behaviour of a natural unsaturated loess from northern France was investigated by running a series of constant rate of strain oedometric compression tests (together with some step loading tests) while monitoring suction by means of a high-capacity tensiometer. The reasonably constant suction measured during constant water compression tests was linked to the collapse of the largest dry pores. Time-dependent behaviour was also observed, with different responses obtained at different strain rates. In a standard fashion, collapse tests appeared to bring the representative point from the constant water content curve to the zero suction compression curve, indicating the existence of a maximum collapse stress. Data were qualitatively interpreted using the loading collapse (LC) yield curve of the Barcelona basic model. Changes in the LC yield curve inclinations could account for the existence of a maximum collapse value.