Frictional and Interface Frictional Characteristics of Multi-layer Cover System Materials and Its Impact on Overall Stability

Abstract

The municipal and hazardous landfills nearing its design capacity need to be isolated from the atmosphere using multi-layered cover system (MLCS). These MLCS constitutes different layers of soil and geosynthetics with widely varying properties. Each of these layers fulfil specific requirements by acting as a surface protection, drainage, separation, filtration and hydraulic barrier layers of MLCS. Failure of these MLCS leads to waste–atmosphere interaction and results in extremely hazardous situation to biosphere. The stability of MLCS significantly depends on the shear strength characteristics of materials used viz., the internal frictional characteristics of individual soil materials and interface frictional characteristics of soil–soil or soil–geotextile combination. In view of this, frictional characteristics of four type of soils, four soil–geotextile interfaces and one soil–soil interface was determined using direct shear and modified direct shear testing methods. The modification of geomembrane used in barrier layer was also attempted, for improving its interface shear characteristics. The usefulness of the above parameters and the influence of its variability on the slope stability of MLCS of a near surface low level radio-active waste disposal facility (NSDF) is demonstrated in this study.