Experimental investigation of the effect of landfill leachate on the mechanical and cracking behavior of polypropylene fiber-reinforced compacted clay liner

Abstract

This paper aims to investigate the effect of leachate on the geotechnical parameters and the cracking behavior of compacted clay liners (CCLs) containing different percentages of polypropylene fibers. Accordingly, 200 compacted clay samples were reinforced with different percentages of fiber contents (FC) (i.e., 0, 0.5, 0.75, and 1%) and prepared with water or leachate to conduct different laboratory tests. First, the physical properties of the clay were determined. Then, the shear strength parameters (i.e., cohesion and friction angle), unconfined compressive strength, and the hydraulic permeability were determined subjected to water or leachate. Notably, the cracking behavior was modeled using visual images of the samples. The leachate increased desiccation cracks in the natural soil from 0.425 to nearly 1.111%. However, the addition of 0.5% (in the case of water) and 1% (in the case of leachate) fiber to the soil reduced the surface desiccation cracks in clay liners to about 0.185 and 0.352%, respectively. In both water- or leachate-prepared samples, the addition of fibers significantly increased the cohesion and friction angle. The shear strengths of the unreinforced leachate-prepared samples were lower than those of the water-prepared samples. The shear strength and unconfined compressive strength of all specimens increased with increasing fiber percentage. The presence of fibers in all samples caused more ductile behavior. The required amount of energy to achieve the maximum strength in the samples increased with increasing FC. By increasing the percentage of fibers, the permeability of the natural soil and the leachate-prepared samples increased. However, the highest permeability was observed in the leachate-prepared samples containing 1% fibers of 8.3 × 10^-10 m/s, which is less than 10^-9 m/s (maximum allowable permeability for clay liners). Finally, the obtained results were satisfactorily confirmed by scanning electron microscopy (SEM) analysis.

Keywords: Compacted clay liner; Cracking; Leachate; Permeability; Polypropylene fibers; Shear strength.