颗粒级配与形状对钙质砂渗透性的影响

钙质砂是富存于热带海洋环境（包括中国南海海域）中的一种特殊岩土介质，具有不同于陆源砂的水理性质。采用传统常水头渗流试验，首先探究了不同不均匀系数和曲率系数条件下级配对钙质砂渗透性的影响。针对钙质砂的颗粒形状特性，采用扫描电镜（SEM）与图像处理技术，引入球度 和圆度X的比值 从三维空间角度上对颗粒形状进行了定量描述。并在粒径区间、相对密实度相同的条件下，通过与福建标准砂、玻璃珠进行对比试验来考察钙质砂渗透特性，从而进一步探究颗粒形状对钙质砂渗透性的影响。试验结果表明，钙质砂渗透性随着颗粒粒径不均匀系数和曲率系数的增大而增大，符合级配对一般砂土渗透性的影响规律；钙质砂颗粒形状具有较强的结构性和不均匀性，同等密实度下钙质砂的渗透性小于陆源的石英砂。本研究获得的钙质砂渗透规律对今后南海岛礁填筑和海上平台基础工程设计具有一定的指导意义。

Effects of particle size distribution and shape on permeability of calcareous sand

Calcareous sand is widespread in tropical marine regions (including the South China Sea). It is one type of special geomaterial with unique hydro-physical properties different from terrigenous sands. Through the conventional constant head permeability tests, the effect of particle size distribution with varied uniformity coefficients and curvature coefficients on the permeability of the calcareous sand has been investigated. In light of the unique shape of calcareous sand particle, the ratio, , of sphericity to circularity X was introduced to quantitatively describe the particle shape based on the SEM images. To explore the effect of particle shape on the permeability of the calcareous sand, an investigation was performed by comparing with Fujian standard sands and glass beads with the same particle size distribution and relative compaction. The test results indicate that the permeability of the calcareous sand increases with the growth of uniformity coefficients and curvature coefficients, being consistent with the effect of particle size distribution on common sands. Compared to the other two kinds of granular materials, the particle shape of the calcareous sand has significantly structural and nonuniform properties, which can significantly reduce the permeability. The results of the present study will provide a guide for the designs of the island building and platform foundations.