Expansive and collapsible soils pose severe risks to civil infrastructure. When expansive clays absorb water, they swell and exert upward pressure on foundations. Conversely, collapsible soils structurally breakdown and settle drastically when wetted.
Initial and final void ratios are calculated using the specific gravity ( Gscap G sub s ) of the soil solids, dry mass ( Mdcap M sub d ), and specimen volume ( Swell or Settlement Strain (
: Used for reconstituted specimens simulating compacted fills. It measures swell pressure and free swell by applying different loads to identical specimens before wetting.
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Civil engineers and geotechnical professionals frequently encounter soils that change volume with moisture variations. These expansive soils can crack foundations, buckle pavements, and damage utilities. To quantify this behavior, the industry relies on , the latest standard for evaluating the one-dimensional swell or settlement potential of cohesive soils.
(such as loosely deposited loess or poorly compacted fills) seem stable when dry but undergo catastrophic structural collapse—known as hydrocompression—upon wetting.
The specimen is placed in the consolidometer at its natural moisture content and subjected to a specific vertical stress (such as the estimated in-situ overburden pressure). Once the specimen stabilizes under the load, it is inundated with water. The resulting vertical deformation (swell or collapse) is measured. Method B: Constant Volume (Swell Pressure) Expansive and collapsible soils pose severe risks to
The acceptable limits for solid content vary depending on the application and industry. However, here are some general guidelines:
This method measures the free swell of a soil sample under a minimal seating load, followed by incremental loading to determine the swell pressure.
This method measures the swell or collapse at a predetermined overburden pressure, followed by load-induced compression. It is often used to simulate the actual loading conditions in the field. Test Method C: Variable Load Swell/Collapse Initial and final void ratios are calculated using
The data produced by these tests is used to estimate the potential for volume change in confined soil profiles. Key applications include:
Intact (undisturbed) or compacted soil samples are trimmed carefully into the specimen ring to minimize disturbance. Initial mass, height, and moisture content are recorded.
Place the specimen into the loading frame between the porous stones.