Design of landfills must consider both stability and integrity of the lining system. Therefore,
stresses and strains in both mineral and geosynthetic lining materials must be controlled.
Interaction between waste and barrier system is of particular importance for assessing the stability and structural integrity of steep non-self supporting barrier systems. The most appropriate
approach to assess the interaction is the use of numerical modelling techniques, and therefore an
appropriate constitutive model for waste material is required to represent its mechanical
In a literature review the key aspects of mechanical behaviour of municipal solid waste (MSW)
were investigated, including the influence of compressible and reinforcing particles on
compression and shear behaviour of MSW were identified. Constitutive modelling of both MSW
and soil material were reviewed, based on which the methodology for this study have been
developed. In addition, requirements of an appropriate constitutive model for MSW have been
suggested from the numerical modelling experience, and a framework to develop a constitutive
model for MSW was produced.
A one-dimensional compression model was developed by including the influence of compressible
particles on MSW compression behaviour. One-dimensional compression tests on both real and
synthetic waste samples were modelled and the results have shown that the compression model
can reproduce the measured behaviour. A fibre reinforcing model was developed by including the
influence of reinforcing particles on MSW shear behaviour. A triaxial compression test on fibre
reinforced sand was modelled and the results have shown that the reinforcing model can predict
its shear strength.
A constitutive model for MSW has been developed by combining the Modified Cam-Clay with
the one-dimensional compression and the fibre reinforcing models. Typical MSW triaxial
compression tests have been modelled and the results have shown that the MSW model can
reproduce the stress-strain behaviour in specific strain ranges. The constitutive model for MSW
has been coded into a non-linear elasto-plastic finite element method program. Comparisons
between the finite element analysis results and the analytical solutions have been performed and
good agreements have been obtained.
A Doctoral Thesis. Submitted in partial fulfillment of the requirements for the award of Doctor of Philosophy of Loughborough University.