Loose, dry, low-density deposits that compact when they are wetted mantle extensive areas in North America, Europe, and Asia. This process, here referred to as hydrocompaction, has produced widespread subsidence of the land surface. Hydrocompaction may occur under natural overburden load or may occur only with the addition of a surcharge load.
Deposits that subside because of hydrocompaction are generally one of two types: (1) loose, moisture-deficient alluvial deposits; and (2) moisture-deficient loess and related eolian deposits. Such deposits occur in regions where seasonal rainfall seldom, if ever, is sufficient to penetrate below the root zone; thus, they have remained moisture deficient throughout their postdepositional history and are readily susceptible to hydrocompaction when they are artificially wetted.
Subsidence due to hydrocompaction is of serious concern in the design and maintenance of aqueducts, buildings, pipe lines, highways, and other major engineering structures. Damage usually can be minimized by precompacting the deposits before construction begins.
