TOWARDS AN ABSOLUTE MEASUREMENT OF SOIL STRUCTURAL STABILITY USING ULTRASOUND

Calibrations enabled controlled application of a range of known dispersive energies to a selected soil sample. The corresponding levels of dispersion were measured in terms of the weight fraction of particles < 2 .mu.m equivalent spherical diameter produced, and are used to define a dispersion characteristic for the test soil. Interpretation of this characteristic in terms of a microaggregate theory provides the energy value associated with complete primary dispersion of micro-aggregates, which under normal field conditions is a direct practical measure of soil stability. This leads to a definition of the specific stability index (.sigma.) of a soil which for the gleyed brown earth used in this work has the value (25 .+-. 3) J g-1.