Measurement of aggregate bond energy using ultrasonic dispersion

Abstract

Numerous protocols have been developed to assess soil stability, such as wet sieving, end‐over‐end shaking and rainfall simulation, but a major limitation of these procedures is that they apply an arbitrary application of mechanical energy that is not quantified, resulting in a stability assessment that can only be related to the context in which it is being used. To address this, previous authors demonstrated that the energy (L) responsible for dispersing soil could be determined when using ultrasonic agitation. Changes in ultrasonic equipment, with the inclusion of a feedback system to adjust the output energy, E_p, of the ultrasonic probe, preclude the assumption that E_pis the same in pure water and in dispersed and undispersed soil–water systems, which may explain why previous approaches have not been routinely adopted. Our paper presents a new theory for estimating the components of the energy balance in an ultrasonic system fitted with a power‐adjusting feedback mechanism facilitating the estimate of L. Using Vertisol and Ferrasol soil samples, the components of the ultrasonic energy balance were successfully estimated and the estimate of L was greater than that reported in earlier work. When used to calculate the soil dispersion characteristic curve, it was found that the critical dispersive energy (L_d) was in the range of 100–600 J g⁻¹, which appears to be much larger compared with previously published values, and the L_dconstituted 3–20% of the total energy applied to the soil–water system.