Experimental research on size effect and avalanche dynamics characteristics of calcareous sand particles

Calcareous sand is widely distributed on the coastal continental shelf and coastline and is the important geotechnical material for coastal engineering. Particle crushing behavior of the calcareous sand brings challenges to the construction of coastal and marine engineering. Single particle compression tests are carried out on the calcareous sand particles with three different average sizes from an island in South China Sea. The test method is mechanical loading with acoustic emission monitoring and real-time observation by optical microscope. The Weibull distribution is used to investigate the single particle strength of the calcareous sand. The size effect is observed on the characteristic strength of the calcareous sand particles. The energy distribution, waiting time distribution and aftershock distribution of acoustic emission (AE) signals are analyzed through the avalanche dynamics statistics. The waiting time distribution and aftershock distribution of the calcareous sand particles with different particle sizes both meet the good power laws and share the same power exponent. For the energy distribution AE, the calcareous sand particles with average particle sizes of 0.9 mm and 1.58 mm demonstrate similar power-law distribution and power exponent (around 1.40), which are both consistent with those of the histogram method and the maximum likelihood estimation method. The power exponent of the calcareous sand with the size of 2.18 mm is significantly larger than that of the particles with other two sizes and exhibits a mixing power law distribution.