Micromechanical Behavior of Granular Soils Characterized by Acoustic Emission

Abstract

Abstract The study of failure mechanisms from a microperspective demands a comprehensive understanding of the initiation and evolution of shear banding within granular materials. However, this topic is not fully understood due to the technical constraints in continuous quantification of the failure degree and visualization of particle interactions within soil specimens due to their inherent opacity. This paper reports the possibility of acoustic emission (AE) technique in characterizing the micromechanical behavior of saturated coral sands subjected to drained triaxial shearing. Results show that coral sand is less emissive than silica sands, while its AE rate forms concrete mathematic relations with soil mechanical parameters, which agrees with those revealed for silica sands. This allows soil mechanical parameters of coral sands that are difficult to be assessed in the field to be back-evaluated by acoustic measuring. The traced AE source locations confirm their spatiotemporal correspondence with the photographed appearance of deformed specimens, in which complex shear banding process, regarding the initiation and evolution, is traced. Three acoustic precursors are observed before the complete soil failure and are considered resulting from the structural variation that affects the emission and propagation of AEs, which hence could be used as indicators for early warning of soil’s instability.