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.
Highlights
Calcareous sand is a special marine soil, which is widely distributed in coral islands and reefs, and has been commonly used as a construction material for offshore hydrocarbon facilities
The results suggest that the incipient failure of strain localization is not always synchronous to but fluctuating at around the peak stress in drained triaxial shearing
Laboratory drained triaxial shearing tests incorporating with acoustic emission (AE) measurement were conducted on saturated coral sands under the confining stress of 100 kPa, 200 kPa, or 400 kPa
Summary
Calcareous sand is a special marine soil, which is widely distributed in coral islands and reefs, and has been commonly used as a construction material for offshore hydrocarbon facilities. The moment regarding the initiation of strain localization, which was normally interpreted as indicative of incipient failure warning soil instability, remains a debated issue [9,10,11,12,13,14,15,16,17]. This is because the technical constraints and the inherent. Sensors were directly attached on the membrane using quick-drying glue into four layers, and information regarding the schematic layout and spatial coordinates of the AE sensors is shown in Figures 3(c) and 3(d) and Table 1, respectively
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