Celik B, Rowe R K, Unlü K
Middle East Technical University, Department of Environmental Engineering, Inonu, Bulvari 06531, Ankara, Turkey.
Waste Manag. 2009 Jan;29(1):103-9. doi: 10.1016/j.wasman.2008.02.012. Epub 2008 Apr 8.
Leakage rates are evaluated for a landfill barrier system having a compacted clay liner (CCL) underlain by a vadose zone of variable thickness. A numerical unsaturated flow model SEEP/W is used to simulate the moisture flow regime and steady-state leakage rates for the cases of unsaturated zones with different soil types and thicknesses. The results of the simulations demonstrate that harmonic mean hydraulic conductivity of coarse textured vadose zones is 3-4 orders of magnitude less than saturated hydraulic conductivity; whereas, the difference is only one order of magnitude for fine textured vadose zones. For both coarse and fine textured vadose zones, the effective hydraulic conductivity of the barrier system and the leakage rate to an underlying aquifer increases with increasing thickness of the vadose zone and ultimately reaches an asymptotic value for a coarse textured vadose zone thickness of about 10m and a fine textured vadose zone thickness of about 5m. Therefore, the fine and coarse textured vadose zones thicker than about 5m and 10m, respectively, act as an effective part of the barrier systems examined. Although the thickness of vadose zone affects the effective hydraulic conductivity of the overall barrier system, the results demonstrated that the hydraulic conductivity of the CCL is the dominant factor controlling the steady-state leakage rates through barrier systems having single low permeability clay layers.
针对一种垃圾填埋场防渗系统评估渗漏率，该系统具有压实粘土层（CCL），其下为厚度可变的包气带。采用数值非饱和流模型SEEP/W来模拟不同土壤类型和厚度的非饱和区情况下的水分流动状态和稳态渗漏率。模拟结果表明，粗质地包气带的调和平均水力传导率比饱和水力传导率小3 - 4个数量级；而对于细质地包气带，差异仅为一个数量级。对于粗质地和细质地包气带，防渗系统的有效水力传导率以及向下方含水层的渗漏率均随包气带厚度增加而增大，对于粗质地包气带厚度约为10m和细质地包气带厚度约为5m时最终达到渐近值。因此，分别比约5m和10m厚的细质地和粗质地包气带，是所研究防渗系统的有效组成部分。虽然包气带厚度会影响整个防渗系统的有效水力传导率，但结果表明，压实粘土层的水力传导率是控制通过具有单一低渗透粘土层的防渗系统的稳态渗漏率的主导因素。
