Lab Services: Soil testing

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Test Method Title

Standard Test Methods for One-Dimensional Swell or Settlement Potential of Cohesive Soils

Reference Number

ASTM D4546

Material

Soil

Test Property

Compression index, swell index

Description of Test

Method A—This method can be used for measuring one-dimensional wetting-induced swell or collapse hydrocompression) strains of compacted or natural soils over a range of vertical stresses. Four or more identical specimens are assembled in consolidometer units. Different loads are applied to different specimens and each specimen is given access to free water until the process of primary swell or collapse is completed under a constant vertical total stress. The resulting swell or collapse deformations are measured. The final water contents and dry densities are also measured. This method can be referred to as wetting-after-loading tests on multiple specimens. The data from these tests can be used to estimate one-dimensional ground surface heave or settlement. In addition, the magnitude of “Swell Pressure,” the minimum vertical stress required for preventing swell, and the magnitude of free swell, the swell strain corresponding to a near zero stress of 1 kPa (20 lbf/ft²) can be interpreted from the test results. Method B—This method can be used for measuring one-dimensional wetting-induced swell or collapse strain of a single “intact” specimen of natural soil, or a single “intact” specimen of compacted soil obtained from an existing fill or embankment. The specimen is loaded to a specific vertical stress, typically the in-situ vertical overburden stress or a particular design pressure, or 1 kPa (20 lbf/ft²) for measuring the free swell strain, and then inundated to measure the wetting induced strain under that particular stress. This method can be referred to as single point wetting-after- loading test on a single specimen. Method C—This method is for measuring load induced strains after wetting-induced swell or collapse deformation has occurred. This method can be referred to as loading-after-wetting test. The results would apply to situations where new fill and/or additional structural loads are applied to the ground that has previously gone through wetting-induced heave or settlement. The first part of the test is the same as in Method A or B. After completion of the swell or collapse phase, increments of additional vertical loads are applied to the specimen in the same manner as in a consolidation test, Test Methods D2435, and the load-induced deformations are measured.

Preferred Test Sample Size

Number of Test Specimens

1

Test Specimen Size

2.87 in diameter x 0.8 in height

Keywords

Expansive soil, heave, settlement, swell pressure, swell index