Application of Shear Strength of Solid Waste and Multilayer Liner in Landfills

Abstract

The scope of this paper is to present the shear behaviors of municipal solid waste and interfaces of composite liner in landfills. The shear strength of solid waste was investigated by triaxial compression and direct shear tests. Triaxial tests are conducted using standard sand sample randomly reinforced by fabric to investigate the influence of fabric length, fabric content on their strength behavior. Test results showed that the sample strength increases with increasing of fabric length when the fabric length is smaller than a certain length threshold. Above this threshold, the fabric length has little effect on the sample strength. Similarly, the sample strength, especially the cohesion, increases dramatically with increasing of fabric content when the fabric content is below a content threshold. Above it, the fabric content has little influence on the strength. Comparison between the fabric length and content showed that the fabric content is more important, as satisfactory sample strength can be obtained even with a small fabric length when the fabric content is above a certain limit. All results of triaxial compression and direct shear tests show that the stress-strain or stress-displacement response for the solid waste has a steady hardening behavior without reaching peak stress condition due to the progressive contribution of the fibrous materials in the waste. It is suggested that the strength parameter of solid waste by triaxial compression test is obtained at the strain of 15%. The direct shear tests were performed to investigate the interface shear strengths for composite liners. The composite liner consists of nonwoven geotextile, HDPE geomembrane and compacted clay. The weaker interface in the composite liner can be transferred from the interface of geomembrane and nonwoven geotextile to the interface strength of geomembrane and saturated clay with increase of the normal pressure. Based on the test results, stability analysis for a failed landfill was conducted.