Particle breakage and morphology changes of calcareous sands under one-dimensional compression loading

Abstract

Particle breakage and the corresponding change of morphology are two key factors governing the mechanical behavior of calcareous sands in offshore geotechnical engineering constructions. To reveal the characteristics of these two factors, oedometer tests on calcareous sands have been performed in this study. The materials were sampled from the South China Sea with a homogenous composition but different particle size ranges and relative densities. In these tests, the dynamic imaging analysis (DIA) by Microtrac PartAn3D and acoustic emission (AE) techniques were employed to investigate the evolution of particle morphology and characteristics of AE signaling associated with the material deformations, respectively. The compressive deformation of calcareous sands was mainly induced by the particle rearrangement and particle breakage which are effectively irreversible plastic deformations. The irregular particle shape has led to strong interparticle filling and interlocking effects, which affected the particle slippage and rearrangement significantly during the deformation. The intensity and type of AE-triggering micro-mechanical behaviors were characterized by AE ringdown counts (RDC) and peak frequency, respectively. The RDC values concentrated primarily in the compression stage and increased rapidly under the normal stress of 400–3200 kPa. The RDC values increased with the increase of particle size but decreased with the increase of initial relative density. The compressive deformation and breakage characteristics of calcareous sands are consistent with the existing acoustic emission laws.