PARAMETERS FOR CHARACTERIZING THE SOIL VOLUME CHANGE AS A FUNCTION OF THE SOIL MOISTURE

The authors discuss the parameters used for characterizing the soil swellingshrinking phenomena and propose new parameters: the coefficient of volumetric expansibility (COVE) and the average coefficient of volumetric variation (ACVV). The coefficient of volume expansibility, COVE, defined as ratio of the difference between the moist bulk (V m ) and the dry bulk (V d ) of a soil clod to the dry bulk: COVE= (V m -V d ) / V d = V m / V d - 1 Practically, COVE is calculated from data about soil bulk densities (BD): COVE= This coefficient is calculated from the same data used for COLE (coefficient of linear extensibility) calculation, but without extracting cubic root from the ratio between dry and moist bulk density. Therefore, there are the following relations between COVE and COLE: (BD d / BD m ) - 1 COVE = (COLE+1) 3 -1 and COLE = (COVE+1) 1/3 -1 The COVE better answers to the evaluation of the magnitude of the soil swellingshrinking phenomena depending on soil moisture and it also express directly bulk variation (expansion) of soil mass and not linear extension. In fact, the COLE (as it as calculated) is an "disguised" COVE, being a ”rectified” (“returned”) COVE (in order to correspond to the definition) by mathematical passing from three-dimensional size to an unidirectional one, an artifice that is properly only if the mentioned phenomena take place isotropically. The average coefficient of volume variation (ACVV) refers to the soil volume variation for one percent of increase of soil moisture. The relation among these parameters are presented together with the interpretation of their values.