Numerous highway embankments experience post-construction settlement problems, such as bridge approach settlement that results in the 'bump at the end of the bridge'. One of the causes may be wetting-induced collapse settlement or simply, collapse settlement. Collapse settlement is a time-dependent process resulting from post-construction increases in moisture content. The post-construction settlement of numerous Oklahoma highway embankments raised questions as to whether the current Oklahoma Department of Transportation embankment specifications and construction practices are adequate in addressing collapse settlement, and prompted the current study to examine the influence of soil type on collapse potential of Oklahoma soils. One-dimensional oedometer tests were conducted to study the potential for collapse settlement of 22 Oklahoma soils and shales under conditions typically encountered in compacted fills. Results show that factors related to fine composition, such as clay-size fraction, plasticity index, liquid limit, activity, and AASHTO group index can be used for preliminary estimation of collapse index. Statistical analysis of the oedometer test data indicates that variables having the most impact on collapse index are moisture content, dry unit weight, plasticity index, and clay-size fraction.
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