Study on mechanism of Oil contamination and remediation in the ground

通过平面应变条件下的模型试验和x射线计算机断层扫描（CT）方法，可视化了轻质非水相液体（LNAPL）在干湿砂土中的迁移过程。为了评估砂土中水分或LNAPL的饱和度，本文提出了一种确定x射线CT图像阈值的新方法。结果表明，砂土的饱和度和颗粒性质改变了LNAPL的迁移机制，且液体的分布形式存在S-p关系差异。饱和度≥20%的沙质土层对LNAPL垂直入渗有抑制作用。近地表保留的水分比LNAPL多。在分级良好的材料中，LNAPL渗透在注入点周围发育。

The migration of Light Non-Aqueous Phase Liquid (LNAPL) in dry/wet sandy soils was visualized by the model tests in plane strain condition and using X-ray Computed Tomography (CT) method. To evaluate the saturation degree of water or LNAPL in the sandy soil, new method to decide the threshold value in X-ray CT image was proposed in this paper. It was concluded that saturation degree and grain property of sandy soil changed the migration mechanism of LNAPL, and the distribution form of liquids differed by S-p relation of liquids. Sandy soil layer with saturation degree at least more than 20% inhibited the vertical infiltration of LNAPL. More amount of water than LNAPL was retained in near-surface. LNAPL permeation developed around injection point in well graded materials.