为了解决传统压实黏土封顶系统在干旱及半干旱地区存在干燥开裂的问题，三种新型的ET (Evapotranspiration) 封顶系统的设计方案被提出了。其中，一种ET封顶系统设计方案的结构由上下各1m厚的植物生长土层和阻隔土层构成，另外两种ET封顶系统分别在中间与底部增设了一层生物阻隔层。在考虑降水与蒸发蒸腾循环补给的条件下，建立了水汽在多层非饱和土壤中迁移的一维数学模型。以1976年大连市全年的降水与蒸发蒸腾强度为边界条件，模拟了水汽在四种封顶系统中的迁移规律。计算结果表明，在传统压实黏土封顶系统中，由于压实黏土层具有极低的渗透性，致使整层土壤不能得到有效的水分补给；ET封顶系统中整个土层可以在降水的过程中有效地从边界得到补给，同时在蒸发蒸腾的条件下，把土层中的储水释放；ET封顶系统设计方案2中设置的生物阻隔层，不仅可以防止生物对阻隔土壤层的破坏，而且起到了排水作用。

In order to solve desiccation cracks of conventional compacted clay cover system in arid and semiarid areas, three alternative evapotranspiration (ET) covers were proposed.One alternative option configuration consisted of 1m vegetation soil layer and 1m barrier soil layer, while two additional alternatives contained biointrusion barriers layer placed at different depths within the structural profile.Considering precipitation and evapotranspiration, a onedimensional moisture transport model through multilayer unsaturated soil was developed.By the case study of four covering systems under precipitation and evapotranspiration intensity of Dalian city at 1976, it was shown that the compacted clay layer of the traditional landfill cover could not get effective moisture charge.ET cover act as a reservoir during precipitation events and subsequently returned it to atmosphere as evapotranspiration.The biointrusion barriers layer located in the second ET cover design would restrict animal movement and play a key role in drainage.Consequently, these results would be used to assist in decisionsmaking of the landfill cover system in semiarid areas.

国家自然科学基金项目(50679015); 中科院武汉岩土力学研究所湖北省环境岩土工程重点实验室开放课题资助项目(T110504)