Acoustic Emission Behavior of Cohesive Soils

In this, the second of a series of three papers on acoustic emission monitoring of soils, cohesive soils are evaluated. A study of acoustic emission fundamentals showed that the amplitude of the emissions in cohesive soils are from ½ to 1/400 of that in granular soils, that frequencies are in the low kiloherz range (predominantly 2 kHz-3 kHz), and that attenuation is high, from 30 dB/ft to 57 dB/ft (1.0 dB/cm to 1.9 dB/cm), and is related to water content. Regarding the macroscopic behavior of acoustic emissions in cohesive soils, the study showed that acoustic emission counts and strain are interrelated, both bearing a definite relationship to the imposed stress level, that increasing water content or plasticity index, or both, decreases the level of acoustic emissions generated, and that stress history effects are reflected in a change of acoustic emission rates. This latter finding allows for acoustic emission monitoring of undisturbed samples for the potential location of the preconsolidation pressure.