Quantification of the Change in Clay Permeability Due to Contamination

废物控制设施设计不当或化学品泄漏的最严重后果是化学品进入地下水供应。分析污染物在土壤中的传输的核心是了解土壤在被化学物质饱和前后的渗透性。这项研究的目的是开发一种预测污染引起的土壤渗透性变化的方法。该项目将寻求开发一种方法，以量化因用一定量的特定污染替换孔隙流体而引起的渗透率变化。粘性土的力学性质在很大程度上取决于孔隙流体的组成。当现有的孔隙水被另一种流体取代时，颗粒间力在某些情况下可能会变得更具排斥力，导致颗粒的分散，但在另一些情况下会变得更有吸引力，导致颗粒团的絮凝和收缩。以水为介质的渗透性试验可以在合理的时间内进行。然而，确定污染引起的渗透率相应变化的直接方法是在实验室对未受干扰的现场样品进行配伍性测试。考虑到各种可能的污染，这一过程非常耗时和昂贵。一种估计渗透率变化的新方法是基于Olsen的集群模型，该模型认识到粘性土壤中的颗粒以集群形式排列，流体通过这种土壤主要通过集群间的孔隙流动。应用于该模型的Kozeny-Carmen方程较好地反映了孔隙度对渗透率的影响。在实验确定了污染前渗透率的基础上，修正的Kozeny-Carmen方程允许计算污染引起的渗透率变化作为簇间孔隙度变化的函数。以前发展的物理化学理论将被用来计算污染引起的团间和团内孔隙度的变化。本研究将使用商业粘土(包括蒙脱石、伊利石、高岭石和混合物)以及两种天然土壤。污染物包括甲酰胺、乙醇、醋酸、三乙胺、庚烷、苯和工业垃圾渗滤液样本。

The most serious consequence of inadequate design of waste containment facilities or a chemical spill is migration of chemicals into groundwater supply. Central to the analysis of pollution transport through soils is knowledge of permeability of the soil, before and after becoming saturated with chemicals. The objective of this research is to develop a method of predicting the change in soil permeability due to contamination. The project will seek to develop a method of quantifying the change in permeability caused by replacement of pore fluid with a certain amount of specific contamination. The mechanical behavior of the clayey soils in this study depends to a great extent on the composition of the pore fluid. When existing pore water is replaced with another fluid, the interparticle force may in some cases become more repulsive, causing the dispersion of the particles, and yet in other cases become more attractive, causing flocculation and shrinkage of particle clusters. A permeability test with water as the permeant can be conducted in a reasonable length of time. However, a direct method of determining a contamination-induced corresponding change in permeability is to perform a compatibility test in a laboratory on undisturbed field specimens. Considering the wide variety of contamination possible, this procedure is very time consuming and costly. A new method to estimate the change in permeability is based on the Olsen's cluster model, which recognizes that particles are arranged in clusters in a clayey soil, and that fluid flow through such a soil occurs primarily through inter-cluster pores. The Kozeny-Carmen equation applied to this cluster model was found to represent reasonably well the influence of porosity on the value of permeability. With the pre-contamination permeability experimentally determined, this modified Kozeny-Carmen equation allows the calculation of the permeability change caused by contamination as a function of the change in inter-cluster porosity. Previously developed physico-chemical theories will be used to compute the change in inter- and intra-cluster porosity caused by contamination. Commercial clays (including montmorillonite, illite, kaolinite, and mixtures) as well as two natural soils will be used in this study. Contaminants will include formamide, ethanol, acetic acid, triethylamine, heptane, benzene, and a sample of industrial landfill leachate.