Relationship between the shrinkage crack characteristics and the water content gradient of compacted clay liner in a landfill final cover

Abstract

Shrinkage cracking is the primary reason for the anti-seepage failure of compacted clay liner (CCL) in a landfill final cover. With a focus on the surface crack characteristics and the water content distribution of three CCLs with different liquid limits and their mineral compositions, experiments were conducted to investigate the cracking mechanism of a CCL during the drying process. The results showed that the total crack ratio (TCR), the sum of the surface shrinkage crack ratio (SCR) and the surface boundary shrinkage ratio (BSR), is a function of the surface water content of a CCL. The change in the TCR with surface water content is consistent with the soil shrinkage characteristic curve (SSCC). The surface SCR is a function of the surface water content gradient of a CCL. The variations in the SCR with the water content gradient can be divided into the following three stages: the crack open stage, the crack linear expansion stage and the crack linear close stage. The effect of sample size, surface boundary shrinkage and shrinkage cracking are the main deformations of CCL specimens with low and high liquid limits, respectively, during the drying process. An increase in the amount of clay minerals in CCLs enhances the soil shrinkage capacity, leading to an increase in the SCR under the same water content gradient. A unified linear relationship exists between SCR/Kj (where Kj is the slope of the SSCC) and the water content gradient in the crack linear expansion stage and the crack linear close stage for different CCL types.