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Swell Potential

Test Method

ASTM Designation: D 4546, “Standard Test Methods for One-Dimensional Swell or Settlement Potential of Cohesive Soils”

Summary of Test Method

The following three alternative test methods require that a soil specimen be restrained laterally and loaded axially in a consolidometer with access to free water.

Method A: The specimen is inundated and allowed to swell vertically at the seating pressure (pressure of at least 1 kPa (20 lbf/ft2) applied by the weight of the top porous stone and load plate) until primary swell is complete. The specimen is loaded after primary swell has occurred until its initial void ratio/height is obtained.
Method B: A vertical pressure exceeding the seating pressure is applied to the specimen before placement of free water into the consolidometer. The magnitude of vertical pressure is usually equivalent to the in situ vertical overburden pressure or structural loading, or both, but may vary depending on application of the test results. The specimen is given access to free water. This may result in swell, swell then contraction, contraction, or contraction then swell. The amount of swell or settlement is measured at the applied pressure after movement is negligible.
Method C: The specimen is maintained at constant height by adjustments in vertical pressure after the specimen is inundated in free water to obtain swell pressure. A consolidation test is subsequently performed in accordance with Test
Method D 2435. Rebound data is used to estimate potential heave.

The relative swell/settlement potential of soil determined from these test methods can be used to develop estimates of heave or settlement for given final moisture and loading conditions. The initial water content and void ratio should be representative of the in situ soil immediately prior to construction. Selection of test method, loading, and inundation sequences should, as closely as possible, simulate any construction and post-construction wetting and drying effects and changes in loading conditions.

Minimum Sample Size

Undisturbed Sample: 1 Tube (1 lb)
Remolded Sample: 2 Canvas Bags (80 lb)

Last Updated September 29, 2005