Department of Civil Engineering, Sharif University of Technology, Azadi Ave., Tehran, Iran.
J Contam Hydrol. 2022 Aug;249:104042. doi: 10.1016/j.jconhyd.2022.104042. Epub 2022 Jun 17.
Clay liners are widely used as porous membrane barriers to control solute transport and to prevent the leakage of leachate both in horizontal and vertical flow scenarios, such as the isolated base and ramps of sanitary landfills. Despite the primary importance of saturated hydraulic conductivity in a reliable simulation of fluid flow through clay barriers, there is no model to predict hydraulic conductivity of clayey soils permeated with saline aqueous solutions because most of the current models were developed for pure water. Therefore, the main motivation behind this study is to derive semi-empirical models for simulating the hydraulic conductivity of clayey soils in the presence of arbitrary solute concentrations in addition to deionized water. In order to achieve this goal, a relatively comprehensive dataset of 842 measured hydraulic conductivities was retrieved from the experimental literature, where almost 44% of them are related to certain solute concentrations. Afterwards, two modelling approaches were introduced; the first one is a modified form of Mbonimpa et al.'s (2002) model, in which the constants are adjusted to take into consideration the variations in liquid limit due to a change in solute concentration. A modification term was added to the model for the sake of accuracy. In the second approach, a new form of solute concentration-dependent hydraulic conductivity function was proposed, where special attention was given to void ratio and adaptive liquid limit as effective parameters. The results revealed that hydraulic conductivity predictions could be erroneous if the influence of solute concentrations in permeating fluid is ignored. An error analysis was conducted to examine the models' applicability and deviations. A blind independent set of data, including 132 data points, was also used to verify models. On the other hand, both newly proposed models could predict the hydraulic conductivity for a variety of soils, salt species, and concentrations well. Therefore, the proposed modelling approaches are somehow unique by considering the salinity of the pore fluid in addition to deionized water. More importantly, both models are comprised of easy-to-measure parameters with clear physics-based implications.
黏土衬垫被广泛用作多孔膜屏障，以控制溶质运移，并防止水平和垂直流动场景（如卫生填埋场的隔离基底和斜坡）中浸出液的泄漏。尽管饱和水力传导率对于可靠模拟通过黏土屏障的流体流动至关重要，但目前还没有模型可以预测渗透有盐溶液的黏土的水力传导率，因为大多数现有模型是为纯水开发的。因此，这项研究的主要动机是推导出半经验模型，以模拟存在任意溶质浓度以及去离子水的情况下黏土的水力传导率。为了实现这一目标，从实验文献中检索到了一个相对全面的 842 个水力传导率测量数据集，其中近 44%与特定的溶质浓度有关。之后，引入了两种建模方法；第一种是 Mbonimpa 等人（2002 年）模型的改进形式，其中常数进行了调整，以考虑由于溶质浓度变化而导致的液限变化。为了提高准确性，在模型中添加了一个修正项。在第二种方法中，提出了一种新的溶质浓度相关水力传导率函数形式，其中特别关注了孔隙比和自适应液限作为有效参数。结果表明，如果忽略渗透液中溶质浓度的影响，水力传导率的预测可能会出现误差。进行了误差分析以检查模型的适用性和偏差。还使用包括 132 个数据点的盲独立数据集来验证模型。另一方面，两种新提出的模型都可以很好地预测各种土壤、盐类和浓度的水力传导率。因此，与仅考虑去离子水相比，所提出的建模方法在考虑孔隙液的盐度方面具有一定的独特性。更重要的是，两种模型都包含易于测量的参数，并且具有明确的物理意义。
