Slope Creep
Adams Stirling PLC


Slope creep is not a process that could reasonably be expected to lead to bodily harm; however, deformation resulting from long-term, slow-rate creep can have a serious effect upon roadways, drainage structures, fence lines, screen walls, retaining walls, utilities, homes, and other improvements. Indicators of creep include tilting and separation of walls in a down slope direction, tension cracks near the top of a slope, and curved trunks of trees which have been growing on a creeping slope for many years.

Creep can occur for various reasons. The most common form of creep is the seasonal expansive soil creep process. This process might be expected to influence the outermost ten to twenty feet of a slope. In a compacted fill slope even deeper expansive soil-related movement can occur. Since expansive soil swelling pressures can easily be in the range of a few to several thousand pounds per square foot, swelling might occur to several tens of feet in depth. In proximity to a slope, long term moisturization will cause the expansive soil to swell and move laterally in the direction of the slope. This process of swelling in the direction of the slope which is referred to by some as lateral fill extension results in the stretching of the building site associated with the soil volume increase.

Slope Softening. Another creep process is slope softening. The slope softening process can occur without significant volume change and without necessarily involving massive or surficial failure. Slope softening tends to be of most concern in compacted fill areas. Slopes change from stiff to soft in response to moisture changing from a drier to a more moist condition.

Information & illustrations courtesy of American Geotechnical, Inc.

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Adams Stirling PLC