The loess in Shaanxi Province exhibits heavy metal contamination

primarily concentrated in the Guanzhong region. In addition

the main heavy metal ions in loess are Pb

Cu

Ni

Cd and As. Among them

the Pb concentration is the highest

reaching up to 545.6 mg/kg. To mitigate pollution spread at contaminated sites

a loess/bentonite cutoff wall was implemented

and its hydraulic conductivity and pollution retardation behavior were experimentally investigated. Experimental results demonstrate that increasing bentonite content in the cutoff wall significantly reduces both hydraulic conductivity () and pollution retardation coefficient (C). To aid in subsequent engineering design

quantitative models for predicting and Cad were formulated. Using this characterization

the minimum bentonite addition required to meet cutoff wall permeability standards was calculated (28.52%)

exceeding the project’s specified value. Consequently

bentonite modification is necessary. Simultaneously

colloid migration during polluted liquid seepage through the cutoff wall was identified

contributing to pollution diffusion and pollution retardation coefficient reduction. Consequently

subsequent research should focus on developing a cost-effective modified material to enhance colloid fineness and reduce its mobility within the cutoff wall. This approach would reduce hydraulic conductivity

improve pollution retardation coefficient

and prevent pollution spread caused by colloid migration.