COMPARISON OF SHRINK-SWELL POTENTIAL OF SEVEN ULTISOLS AND ONE ALFISOL USING TWO DEFFERENT COLE TECHNIQUES1

Abstract

The coefficient of linear extensibility (COLE), used to estimate the shrink-swell hazard of natural soil fabric, requires that intact soil clods be collected when near saturation or be rewetted. Clods must be coated with saran, and significant laboratory equipment is needed to determine the clod shrinkage. A shrink-swell test is needed that can be used in a nonlaboratory setting to evaluate the shrink-swell potential of soils prior to the design of buildings, septic tank subsurface absorption systems (ST-SAS), and other structures. A technique for estimating COLE by extruding a soil paste in the shape of a rod (COLErod) and measuring shrinkage with drying is evaluated as an estimator for COLE determined with the standard technique (COLEstd) for a group of Ultisols with a range of physical, chemical, and mineralogical properties. The COLE values of 39 discrete samples were determined by both techniques. The samples were collected from B and C horizons of eight soil types at multiple sites per soil type. COLErod is a highly significant estimator (R2 = 0.55, p < 0.001) of COLEstd. Variability is probably due to loss of soil fabric when determining COLErod, as well as limited precision with both techniques. COLErod agreed well with the similar linear shrinkage test (r2 = 0.96, p < 0.001), further suggesting that the COLErod methodology is acceptable.