Numerical modelling of landfill lining system–waste interaction: implications of parameter variability

Abstract

Numerical modelling techniques can be used to examine the serviceability limit states of landfill side-slope lining systems in response to waste placement. A study has been conducted in which the variability of significant model input parameters have been investigated within a probabilistic framework using Monte Carlo simulation. Key model parameters are treated as random variables, and the statistical information required to describe their distributions has been derived from a laboratory repeatability testing programme, a literature survey and an expert consultation process. Model outputs include relative shear displacements between lining components, and tensile strains in the geosynthetic layers that occur in response to staged placement of waste against the side slope. It was found that analyses including input parameter variability were able to identify mechanisms influencing liner performance and their probability of occurrence. These mechanisms include large (i.e. )100 mm) relative displacements at interfaces that can generate post-peak strengths, and mobilised tensile strains in the geomembrane and geotextile layers. Additionally, it was found that relative displacements at the controlling (i.e. weakest) liner interface are greater for landfills with a steep side slope, for stiffer waste and thicker waste lifts, while tensile strains in the geosynthetic elements are greater for steep side slopes, more compressible waste and thinner waste lifts. Outputs from probabilistic analyses such as that used in this study can guide engineers regarding geometries and materials that could produce waste-settlement-generated serviceability limit state failures, and hence can be used to support more reliable designs.

System Effects on Bioreactor Landfill Performance Based on Coupled Hydro-Bio-Mechanical Modeling

“…Moreover, the shear strength and the stiffness properties of the interface were adopted from previous studies (Wasti and Ozduzgun 2001;Sia and Dixon 2012).…”

State-of-the-art report: GCL shear strength and its measurement – ten-year update

“…Displacements in liner systems Shear displacements occur within landfill liner systems due to a variety of mechanisms, including construction activities (McKelvey 1994), thermal expansion/contraction, mobilization of passive resistance of a waste buttresses on a base liner (Stark and Poeppel 1994), strain incompatibility between waste materials and geosynthetic interfaces (Reddy et al 1996;Eid et al 2000), earthquakes (Kavazanjian et al 2011), waste placement procedures (Yazdani et al 1995;, and waste settlement (Long et al 1995). For example, displacements along a bottom liner system are generally assumed to be nonuniform and progressive (Byrne 1994;Stark and Poeppel 1994;Gilbert and Byrne 1996;Reddy et al 1996;Gilbert et al 1996b;Filz et al 2001;Jones and Dixon 2005;Dixon et al 2012;Sia and Dixon 2012). Shear failure will occur at the interface with the lowest peak strength, which may or may not correspond to the interface with the lowest residual strength.…”

Landfill side slope lining system performance: A comparison of field measurements and numerical modelling analyses

“…Fowmes et al 2005;Arab, 2011;Sia and Dixon, 2012). The code allows materials that undergo large strains to be modelled, and hence is appropriate for use in studies of landfill construction processes.…”

“…Studies have been carried out to investigate these phenomena, to incorporate these aspects in numerical analyses (e.g. Arab, 2011;Sia and Dixon, 2012;Fowmes et al 2005) and some limited number of physical experiments have been carried out (e.g. Villard et al, 1999;Fowmes et al, 2008).…”