Numerical modelling of lumpy clay landfill

Abstract

SUMMARYTwo trial motorway embankments built on a landfill consisting of clayey lumps were monitored over the period of 3 and 5 years, respectively. The subsoil of the embankment was instrumented by hydrostatic levelling profiles, pore pressure transducers and depth reference points installed in boreholes. An advanced constitutive model for clays (hypoplastic model for clays with meta-stable structure) was used for numerical modelling of both case histories. Basic hypoplastic model for clays was calibrated using isotropic compression tests and triaxial compression tests on reconstituted clay. Three additional model parameters describing the effects of lumpy structure were calibrated using oedometer tests on specimens prepared from scaled-down lumpy material (material with smaller size of clay lumps). The performance of the model was evaluated by comparison with the results of the centrifuge model of self-weight consolidated landfill. Finally, the hypoplastic model was used for simulation of both trial embankments and the results were compared with in situ measurements. The degradation of the lumpy structure of the upper layer of the in situ landfill due to weathering was back analysed using monitoring data.

Modeling swelling–shrinkage behavior of compacted expansive soils during wetting–drying cycles

“…For example, Cui et al (2002) assumed realistically that the role of macroporosity in swelling of dense compacted soils may be neglected, and developed a global mechanical model based on the microstructural model. Similarly, Koliji et al (2008) and Najser et al (2012) described the behavior of double porosity lumpy soils using a model based on the microstructural behavior, with phenomenological incorporation of the influence of macrostructure.…”

Analysis of the compression behavior of artificial lumpy composite materials

“…The overall effective mean stress can also be calculated from the volumeaveraged stresses of the constituents with the volume fraction according to Eq. (6). The overall strain is defined similarly to those of its constituents:…”

Laboratory investigation of artificial lumpy materials

“…After several years from filling, mainly due to the influence of climate, gravitational effect and precipitation, the originally high interlump porosity clays in landfills tend to become relatively homogeneous soils (Figure 1(b)). However, even more than 10 years after filling, their corresponding double porosity still remains (Masin et al, 2005;Najser et al, 2010Najser et al, , 2012.…”

“…In many parts of the world, the large-scaleopencast coal mining has resulted in depositing the clayey overburden in non-engineered landfills (Herbstova and Herle, 2009;Najser et al, 2012). These kinds of landfills usually reach depths of several tens of metres.…”