Experimental research on the evolution laws of soil fabric of compacted clay liner in a landfill final cover under the dry-wet cycle

This paper aims to investigate the structural damage in compacted clay liner (CCL) caused by the dry-wet cycles in a landfill final cover. Experimental research is performed on the microstructure evolution of CCL under repeated dry-wet cycles and different initial compactness (90, 94, and 98 %). Results show that the pore size distribution of CCL has multifractal characteristics which can be classified into five self-similar intervals: macropore (> 15 mu m), medium-pore (8-15 mu m), small-pore (0.3-8 mu m), mesopore (0.04-0.3 mu m), and micropore (< 0.04 mu m). The compression proportion of the different intervals is not equal and constant with the increase in compactness. Maximum compression interval is observed among small-pores and mesopores, with compactness ranging from 90 to 94 % and from 94 to 98 %, respectively. The effect of the dry-wet cycles mainly focuses on small-pores, medium-pores and macropores, while having little effect on meso-pores and micro-pores. The increase of macropores is one of the reasons for increase in the permeability of CCL, but it is not the main reason. Cracks causing by the irreversible shrinkage of pores is the main reason leading to permeability with an orders of magnitude increment, and improving the compactness can reduce the structural damage of CCL under the function of dry-wet cycles.