Abstract: Based on a tailor-made transparent model box and the close-range photogrammetry technology, compression and particle crushing characteristics of calcareous sand are explored through confined compression tests. Results show that the compression deformation of calcareous sand undergoes three stages: The first one is an initial compaction stage under low vertical stress where deformation is dominated by particle rearrangement, leading to a decrease in the volume of inter-particle pores; In the second stage dominated by grinding and angular rupture of sand particles under medium stress, the crushing destroys the interlocking and friction between sand particles to a certain extent, and makes the deformation develop further; In the third stage of overall particle crushing under high stress, the calcareous sand sample is dense and its deformation is controlled by overall particle crushing. The sand particles are broken into a larger number of small ones and the pores are released. Different particle sizes imply different particle crushing modes, but all the samples with a particle size greater than 5 mm undergo a full three-stage process under the conditions of test stress (σmax < 6 MPa).

Key words: calcareous sand, particle crushing mode, pore change, close-range photogrammetry