Regional differences in influence of intermediate cover permeability on perched leachate in landfill

Intermediate cover may act as impervious layers in landfill and form perched leachates, which have adverse effects on the safe operation of landfill. The formation rules of perched leachate mound in different climate regions are not the same and still unclear. To solve this problem, a finite difference method that took account of climate boundaries was conducted. Four typical cities' climate data standing for Chinese climate and 4 permeability parameters of intermediate cover were used in the simulation. The results showed that key to the formation of perched leachate is that the infiltration rate of the leachate is greater than the ks of the intermediate cover. Under arid climate conditions, the infiltrates of the leachate are generally lower than the infiltration capacity of the intermediate cover, and it is not easy to form a perched leachate mound. In humid regions, when the ks of the intermediate cover is lower than 10(-5) cm/s, perched leachate forms easily in rainy seasons. The result can be useful to determine the permeability parameters of intermediate cover, especially in humid climate.