南海钙质砂微观构造三维图像分析与表征

3D image analysis and characterization of morphology of calcareous sand in South China Sea

将侧限压缩试验与CT断层扫描技术相结合,获取钙质砂样本在压缩过程中的三维图像,采用自适应分水岭法对图像中颗粒进行分割,获取颗粒尺寸、形状(球度、凸度、棱角度等)和主轴方向等基本信息,对土样微观形态进行三维表征,并对颗粒形状与尺寸参数进行相关性分析;同时,基于膨胀算法获取颗粒间接触网络,并对受力过程中颗粒配位数及接触方向演变特性进行分析。研究结果表明:钙质砂颗粒形状和配位数与其尺寸存在明显相关性,本研究可为钙质砂本构模型开发与离散元数值模型验证提供参考。

In situ confining compression test on a calcareous sand sample was conducted in a computed tomography(CT) scanner, to obtain three dimensional images that capture the evolution of the morphology at particle scale. An adaptive segmentation technique was implemented to segment the grains in the image, based on which statistical data of the grain sizes and shapes(sphericity, convexity, angularity, etc.) was obtained. This enabled quantitative analysis of the correlation between shape and size parameters. Meanwhile, the contact network among the grains was obtained using a purpose-designed algorithm, and the variation of coordination number and contact direction were analyzed. The results show that the grain sizes are relevant to its shapes and coordination number. This study intends to provide reference data for the validation of constitutive models for calcareous sand, as well as relevant discrete element models.