钙质砂压缩过程中颗粒破碎的细观特征

本文采用自设计的透明模型箱，通过侧限压缩试验，结合近景摄影测量技术，探究了钙质砂的压缩与颗粒破碎特征。试验表明，钙质砂的压缩变形可以分为三个阶段：低应力下的初始压密阶段，变形以颗粒位置调整使得颗粒间孔隙被压缩为主；中等应力下的研磨和棱角破裂阶段，变形以颗粒研磨和棱角破裂的破碎模式为主，一定程度上破坏了钙质砂颗粒间的咬合力和摩擦强度，使得变形进一步发生；高应力下的整体破碎阶段，钙质砂颗粒以整体破碎的模式主导钙质砂试样的变形，钙质砂颗粒整体破裂成大量的小颗粒，钙质砂内孔隙被大量释放，钙质砂试样进一步被压密。不同粒径的钙质砂压缩破碎的模式不同，在试验应力条件下（σmax < 6 MPa），粒径大于5 mm的钙质砂试样压缩过程中会经历上述完整的三个阶段。

Meso characteristics of particle crushing of calcareous sand during compression

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).