Abstract: In the current design of anti-seepage projects using compacted clay layers (CCL) against oily pollutants, the criterion that the hydraulic conductivity of water in CCLs should be less than 10-7 cm/s may be abused. In this paper, we performed oil (0# diesel and 93# gasoline) and water alternate seepage through CCLs of Yunnan Province, China. The results show that (1) under different seepage pressure, the hydraulic conductivity of water ranged (0.412.52)×10-8 cm/s, indicating the Yunnan clay can be used as natural anti-seepage lining; (2) critical hydraulic gradients for 0# diesel and 93# gasoline seepage through water-saturated CCLs were 0.05 and 0.02 MPa, respectively; once the critical hydraulic gradient was broken, the permeability of CCL increased rapidly and hydraulic conductivity of oily pollutants was 13 orders of magnitude higher than that of water; (3) in the process of water seepage through 0# diesel or 93# gasoline filled CCLs, the hydraulic conductivity of water was (10-710-6) cm/s; oil-soaked CCLs could not serve as anti-seepage lining again; and (4) the current standard for anti-seepage design against oily pollutant requires that hydraulic conductivity of water in CCL to be less than 1×10-7 cm/s, which is not applicable; the level of CCLs anti-seepage performance should be improved.

Key words: hydraulic conductivity, compacted clay layer, diesel, gasoline, anti-seepage