粒组含量对钙质砂压缩变形特性影响的宏细观研究

钙质砂是一种海洋生物成因的特殊岩土介质，其颗粒形态与基本性质较一般陆源砂有很大的不同。一方面通过钙质砂及石英砂的显微镜三维成像试验，对比研究了钙质砂的三维颗粒形态特征。发现相比石英砂，钙质砂颗粒棱角更显著，轮廓趋于扁平。另一方面，对两砂进行一维压缩试验，分析了各粒组含量对钙质砂压缩特性的影响规律，并利用三维形态分析从细观上解释了钙质砂的压缩宏观特性。发现相同级配、密实度下，钙质砂的压缩性比石英砂高约60%～160%（以av1-2表征），且粗粒组（5～1 mm）含量对钙质砂的压缩性影响最为显著；当粗粒组含量<25%，中、细粒组质量比值M一定时，存在最劣粗粒含量使钙质砂压缩性最大，且该值随着M的增大而减小，并提出了一个经验公式。

Macro-micro study of compressive deformation properties of calcareous sand with different particle fraction contents

Calcareous sand is a special type of rock soil developing in the ocean. This marine sediment with irregular shape has different mechanical properties from the land originated sand. On one hand, microscopic 3D imaging was conducted in this paper for comparing the micro properties of calcareous and quartz sands. It can be found that calcareous sand particles are multi-angular and flatter in comparison with quartz sand. On the other hand, the effect of different particle fraction contents on compressive deformation properties of calcareous sand was investigated in compression tests. Then the 3D morphology was used to discuss the effect mechanism from a microscopic viewpoint. Quartz sand was used as a reference for comparison. It is shown that the compressibility of calcareous sand is 1.6-2.6 times that of quartz sand under the same gradation and compactness. The effect of the coarse fraction (5-1 mm) content in the gradation plays the most significant role in this feature. When the content of coarse particles is less than 25% and the mass ratio of middle and fine particles (M) is constant, there is the worst coarse fraction content causing the greatest compressibility of calcareous sand. With the increase of the mass ratio of middle and fine particles, the worst coarse fraction content decreases, and an empirical formula is proposed.