Estimating Thaw‐Strain Settlement of Frozen Fill

In fill that is frozen, ice acts as a lightweight solid and occupies space that would otherwise be a void or filled with soil particles. Therefore, a fill's dry density (density of solid particles) will decrease as ice content increases. Compacting with a normal, smooth‐drum, vibratory roller has little effect on the dry density of frozen fill with an ice content greater than 6%. A frozen fill's ice content can be reduced, and dry density thereby increased, by processing it in a kiln. Results of laboratory tests indicate that frozen‐fill dry density can also be increased by dynamic compaction. Thaw strain occurs when ice melts in frozen fill. During thaw strain, soil particles settle from their initially frozen dry densities to their loosest thawed dry densities. This loosest thawed dry density has been called the settled dry density. Expected thaw‐strain settlement increases with increasing ice content. Fill with a dry density greater than the settled dry density has the lowest thaw‐strain potential. Methods are presented to estimate thaw‐strain settlement that will occur when ice melts in fill.