Volume 27, Issue 6 (November 2004)
Volumetric Shrinkage Strain Measurements in Expansive Soils Using Digital Imaging Technology
Expansive soils undergo large volumetric shrinkage strains, which eventually lead to high heave movements upon hydration of these soils. Current test methods to determine shrinkage strain potentials of soils are restricted by several limitations including small specimen sizes, molds with rigid walls that restrain shrinkage strains in lateral directions, and manual measurement errors. In this paper, a novel methodology to conduct volumetric shrinkage strain test on cylindrical soil specimens and a digital imaging technique to analyze and determine volumetric shrinkage strains of the test are described. As part of the evaluations of this methodology, volumetric shrinkage strains of four types of medium to high expansive soils were researched. Shrinkage tests were conducted on all four soils at three different moisture contents. Volumetric shrinkage strains were then measured using both digital and conventional manual approaches. Test results showed that the test and the developed measurement methodology provided repeatable and realistic shrinkage strain measurements. Digital measurements provided more accurate results than manual measurements by accounting for even minor shrinkage cracks in the soils. The significance of the digital measurements in relation to the current shrinkage strain characterizations is discussed. Potential geotechnical application areas where these test results could be used are also described.