饱和度-压力曲线法预测柴油在毛细带中形成的透镜体厚度

轻非水相液体（LNAPL）进入到地下环境中，首先在非饱和带进行垂向迁移，到达毛细带后在地下水面以上形成饱和透镜体。准确预测LNAPL渗漏在毛细带形成的透镜体厚度，对于LNAPL的去除及污染含水层的修复具有重要的指导意义。通过模拟实验测定了水-油两相吸湿及脱湿曲线，采用水-油饱和度-压力曲线拟合出了吸湿及脱湿进入压力。根据透镜体达到稳定状态时脱湿、吸湿压力水头之间的关系，建立了透镜体厚度的预测计算方法，并以中砂和粗砂为例，预测出实验条件下柴油在毛细带形成透镜体稳定时的厚度分别为4.61 cm和1.29 cm。通过室内模拟槽实验，测得柴油在中砂和粗砂中迁移时形成的透镜体厚度分别为5.30 cm和1.50 cm。预测与实验结果的相对误差分别为13.0%和14.0%。误差产生的主要原因为脱湿与吸湿曲线是在非干燥情况下测得，从而导致预测的透镜体厚度偏小。

Estimation of Lens Thickness of LNAPL Using Saturation-Pressure Curve

After entering underground, light non-aqueous phase liquid (LNAPL) will firstly migrate vertically in unsaturated zone, and then form a saturated lens above the water table when reaching the capillary zone. Precisely predicting the lens thickness in the capillary fringe is of great significance for the restoration of polluted aquifer. The authors measured the initial drainage curve and initial wetting curve of the water-oil phase through laboratory experiment, and then fitted the entry pressure with the saturation-pressure curve. According to the relationship between the drainage entry and wetting entry pressures when the lens become stable, a method to predict the thickness of the lens was established. A case study of medium sand and coarse sand shows that the predicted thickness of the lenses are 4.61 and 1.29 cm,respectively;while by laboratory experiments, the measured lens thickness are 5.30, 1.50 cm, respectively. The relative errors between the predicted and measured results are 13.0%, 14.0%, respectively. We can hardly get the absolute drainage or wetting curves in laboratory, therefore the lens thickness predicted is smaller than measured in laboratory.