The waterproofing properties of compacted clay barrier at landfill site will be greatly weakened by crack which is induced by the waste’s differential settlement. In order to reveal the effects of preferential flow on the anti-seepage performance of cracked barrier

the crack is treated as high-permeable porous medium

and a simplified saturated/unsaturated seepage model of the barrier with a single crack is developed to study the process of preferential flow. In addition

the influence of crack position

depth

width and permeability coefficient on the anti-seepage performance of the barrier is comparatively analyzed. The results show that the infiltration process can be divided into three stages: early stage

penetrating stage and steady stage. Besides

the bottom crack has little influence on the barrier’s anti-seepage performance

but it is greatly affected by upper or fully penetrated crack. The breakthrough time will be significantly shortened with crack depth increasing until the crack is thoroughly penetrated; and it is better to keep the crack depth under 0.1 time of the barrier’s thickness to ensure its anti-seepage performance. What’s more

with the increase of crack width and permeability coefficient

the water breakthrough time will be rapidly shortened and the steady leakage will increase respectively; and they tend to be stable when they are reaching a certain value. It also shows that the barrier’s anti-seepage performance would significantly deteriorate as soon as the crack is fully penetrated; and the steady leakage will increase linearly with the increase of crack width and permeability coefficient.