ABSTRACT:

Liner systems of landfills placed on slopes are subjected to stress due to displacements of waste. Waste displacements result from settlements and from subsidences of waste material in the landfill. By means of finite element analysis an inclined landfill liner system is studied. Of particular interest is the sliding behaviour between the different layers of the liner system as well as the stress-strain relation in the different layers. Numerical results show that sliding, which is significantly dependent on the inclination as well as on the angle of friction between the layers and furthermore is a function of time, occurs approximately in the upper two thirds of the slope. Tensile strains appear in the geomembrane: the maximum amount of tensile strains occur at the foot of the slope due to an arching effect in the waste body as a result of biodegradation.

INTRODUCTION

A common composite system of a landfill liner consists from top to bottom of a granular drainage layer, a geotextile, a geomembrane and a compacted clay liner. Displacements at the liner systems and therefore, investigations about external forces and their consequences to landfill liner slopes are indispensable in order to predict the functionality of liner systems and the long-term safety of the landfill respectively. The knowledge of sliding, which might occur between the layers of the inclined landfill liner system, of the stresses and strains in the geotextile, which have to be sufficiently low to ensure the protection of the geomembrane, of the magnitude of strains in the geomembrane, which have to be less than 3 %, and of the stresses in the mineral liner, which may lead to excessive cracking, is essential for estimation of the long-term stability and functionality of inclined landfill liner systems.

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