Study On The Evapotranspiration Cover For Landfills In Lanzhou Area

China’s current solid waste sanitary landfill technical specifications (CJJ17-2004), as well as the world’s landfill standards, has an implicit assumption of heavy precipitation, so that strict design top seal and bottom lining impervious system are needed to control leachate and landfill gas pollution to the environment. At the arid or semi-arid with scarce precipitation and strong evaporation, this design principle implies an "excessive defense". Ignored regional differences in climate, the country to adopt a unified design patterns, not only unscientific, but also increase the cost of garbage disposal of the arid and semi-arid regions. Therefore, arid and semi-arid regions, need an alternative cap layer. Evapotranspiration(ET) cover is such a suitable alternative cap in arid and semi-arid regions.Evapotranspiration cover works with a very cleverly use of unsaturated soil "capillary pores absorbent" and "atmospheric evaporation pump" principle, allowing the limited infiltration of precipitation. Its design goal is to prevent the infiltration of water through the cap by means of evaporation. Compared to the traditional standard cap, evapotranspiration cover has some advantages such as low cost, easy construction, easy maintaince.This thesis takes Lanzhou as an example represeting landfill site at semi-arid area. Geotechnical tests were conducted to obtain basic physical paremeters of loess; The soil water characteristic curve tests were used to obtain field capacity and wilting point of loess. Meteorological data were collected from Lanzhou University Semi-arid Climate Observatory and Laboratory. After processing of meteorological data, Hydrus-1D software was used to simulate. Firstly, the silty clay cover was simulated under Lanzhou meteorological conditions, and compared with standard cover, the result shows that it is necessary to seek alternative cover of lanfills final cover design in Lanzhou area. Secondly, taking loess as cover materials, discussing the relationship among the evapotranspiration cover, loess dry density and hydraulic conductivity, and then the evapotranspiration which was simulated was compared with the standard cover. The result shows that loess alternative is feasible in theory.