Collapse of Compacted Clayey Sand

Compacted soils wetted under load can both swell and collapse (subside) depending on their condition and the magnitude of the vertical overburden stress. One‐dimensional compression tests were conducted to clarify the influences of compaction method, compaction water content, relative compaction, vertical stress level, and load‐wetting sequence on post‐compaction wetting‐induced volume changes in a moderately plastic clayey sand. Compaction method and load‐wet sequence had only a minor effect on wetting‐induced collapse. The double‐odometer test was judged to be sufficiently accurate for use in evaluating wetting‐induced collapse. Both swelling and collapse were reduced or eliminated by compacting the soil at water contents on the wet side of the line of optimums for impact compaction. Collapse, but not swelling, could also be reduced by compacting the soil to high levels of relative compaction. By plotting isograms of volume changes in the compaction water content‐relative compaction space, combinations resulting in no wetting‐induced volume change were identified for various vertical stress levels corresponding to the values existing in large fills and embankments.