Mechanical behavior of unsaturated compacted Iowa loess

The collapsible soils possess a high apparent strength at their low natural moisture content but undergo large reduction in volume upon wetting. The volume change and shear strength behavior of a laboratory compacted loess soil was studied and presented. Collapse tests and partial collapse tests were conducted using conventional oedometer. Undrained shear strength was measured from Torvane shear tester. Penetration tests were also performed on collapsible soil specimens. Undrained cohesion, c[Subscript u], was obtained from the measured values of penetration resistance using Sanglerat\u27s equation. Correlations were proposed to relate collapse potential with the penetration resistance. Tests were conducted to determine the variation of water content with suction for loess. The unsaturated soil behavior was investigated for nine conditions produced by varying initial water contents and compactive efforts. The initial water content was replaced with suction and the effect of initial suction on the collapse potential was studied. The collapse potential of loess was found to be dependent on the initial water content, initial dry unit weight and flooding stress (vertical stress at inundation). The amount of partial collapse increased with increase in degree of saturation. The effect of variation in initial water content was more significant as compared to the effect of compactive effort on soil water characteristic curves. Undrained cohesion obtained from Torvane shear tests and penetration tests were found to tally and to give a good correlation. The collapse potential increased with increase in initial suction. However, the percentage increase in collapse on increasing suction reduced as the compactive effort increased