Particle breakage mechanism and particle shape evolution of calcareous sand under impact loading

Exploring the meso-fabric characteristics of calcareous sand (CS) is of vital importance for predicting its macro-mechanical responses under impact loading. To reveal the particle breakage mechanism and particle shape evolution of CS under impact loading, multiple impact tests were conducted on CS under different numbers of impact tests (or cumulative impact energy levels). Screening tests and particle shape scanning tests were used to measure the particle gradation and shape of CS before and after impact testing, respectively. According to the results: (I) CS particles 2−5 mm in size showed the largest breakage extent with increasing number of impact tests. Breakoff and abrasion were the primary CS particle breakage modes under impact loading. (II) Particle size obtained from particle shape scanning tests was mostly smaller than that from sieving tests; and different measuring principles for these two tests and irregular particle shape of CS constituted the direct and essential cause of this result, respectively. (III) The relative change ratio of the particle shape parameter was proposed to quantify variations in CS particle shapes with increasing number of impact tests, and CS particle shapes became increasingly regular with increasing particle breakage.