Field Performance of Compacted Amended Clay Liners at an Industrially Polluted Site

A series of pilot-scale field and laboratory tests were conducted to compare compacted unamended and amended clay liners. The compaction process required at least four passes using a vibrating rammer to meet the specified requirements. After amendment, the cone index and the associated unconfined compressive strength increased. The hydraulic conductivity of the compacted attapulgite/diatomite-amended clay liner was reduced by half using double-ring infiltrometer. The oxygen diffusion coefficient of compacted attapulgite/diatomite-amended clay liner was nearly halved, reflecting reduced gas diffusivity. This improvement resulted from rod-shaped attapulgite filling the inter-aggregate pores formed by clay particles, whereas the disc-shaped diatomite particles failed to obstruct due to their larger particle size, leading to volumetric reduction of inter-aggregate pores. Variations in temperature and volumetric water content of different compacted clay liners showed that the amended clay liners retained more water, enhancing barrier properties due to the hydrophilic groups and microstructures of attapulgite and diatomite.