Part 3Part 3

Behavior of Behavior of Overconsolidated Overconsolidated

ClayClay

Normal versus Normal versus Overconsolidated clay Overconsolidated clay

behaviorbehavior

Clay retains a Clay retains a “memory” of its load “memory” of its load historyhistory

The The effective cohesioneffective cohesion of of overconsolidated overconsolidated clayclay can be significant can be significant

The effective cohesion The effective cohesion can be lost through can be lost through subsequent wettingsubsequent wetting, , especially, load cycling especially, load cycling with with moisturemoisture

Mohr Circle plot of a typical Mohr Circle plot of a typical overconsolidated clayoverconsolidated clay soil, illustrating the artificially high cohesion soil, illustrating the artificially high cohesion engendered by tortuous desiccation. Note the engendered by tortuous desiccation. Note the apparent preconsolidation pressure caused by the apparent preconsolidation pressure caused by the severe shrinkage. severe shrinkage.

The fundamental problem with slabs-on-grade on The fundamental problem with slabs-on-grade on expansive soils is expansive soils is differential swelldifferential swell beneath the corners, beneath the corners, sides, and under the center of a uniformly-loaded slab, sides, and under the center of a uniformly-loaded slab, as sketched here. as sketched here.