To ensure stability of a construction the physical properties of its components have tobe well known. In a landfill, waste presents the largest structural element and controlsboth the stability and integrity of the lining system. In spite of this critical role there is adearth of knowledge on behaviour of waste as an engineering material. Wastevariability and changes in waste stream aggravate the assessment of wastemechanical properties.In a literature review the main influences on shear behaviour of municipal solid waste(MSW) were identified. Design values and recommendation for shear parameter weresummarised. To assess mechanical behaviour in a systematic way the use of aclassification system was deemed crucial for a comparison of different findings fromliterature and a categorisation of waste in regard to its composition. A framework for aclassification system was introduced. Main elements of a comprehensive classificationsystem were identified in a literature review and discussed, and data from literaturewas applied to the classification framework. For the validation of a classificationsystem, municipal solid waste was examined in an in-situ waste sorting analysis andalso applied to the framework.The findings from the waste sorting and the classification system were also used todevelop a family of synthetic waste to gradually examine the influencing factors onwaste mechanical behaviour. For this, the materials, size ranges and shapes of wastecomponents identified in the waste sorting analysis were reduced to a minimum butstill representative amount. A range of synthetic waste compositions was engineeredand tested in a large-scale shear device. Compression tests were also conducted in alarge compression cell. The results from the laboratory testing were compared tovalues from the literature and MSW mechanical behaviour was subsequentlydiscussed in view to potential changes from changing waste streams.The results from shear and compression tests (constrained and shear modulus) onsynthetic waste were linked to the classification system and trends of the mechanicalbehaviour in relation to the tested synthetic waste compositions were identified.A framework for classifying MSW and comparing waste mechanical behaviour waspresented and demonstrated. A family of synthetic wastes was engineered and testedin shear and compression tests. The results were comparable to values from theliterature. Further research is recommended to refine the synthetic waste and theclassification.

Large voids created by underground mining are backfilled to provide regional ground support. This thesis examines using conventional oedometer techniques and electromagnetic (EM) techniques to characterize consolidation and binder hydration in mine backfill so that EM monitoring can be used in the field to provide real-time feedback to operators to optimize the backfilling process. New techniques are given for interpreting the full range of deformation (initial compression, primary and secondary consolidation). Deformation due to initial compression is non-trivial and may have to be accounted for in numerical back-analyses of field case studies. EM parameters are sensitive to binder content, progress of hydration and loss of water caused by consolidation and binder hydration. The integrated interpretation of consolidation and EM behaviours has significant potential impact on real-time monitoring of mine backfill operations, and recommendations are made to advance the technique for this purpose.

Large voids created by underground mining are backfilled to provide regional ground support. This thesis examines using conventional oedometer techniques and electromagnetic (EM) techniques to characterize consolidation and binder hydration in mine backfill so that EM monitoring can be used in the field to provide real-time feedback to operators to optimize the backfilling process. New techniques are given for interpreting the full range of deformation (initial compression, primary and secondary consolidation). Deformation due to initial compression is non-trivial and may have to be accounted for in numerical back-analyses of field case studies. EM parameters are sensitive to binder content, progress of hydration and loss of water caused by consolidation and binder hydration. The integrated interpretation of consolidation and EM behaviours has significant potential impact on real-time monitoring of mine backfill operations, and recommendations are made to advance the technique for this purpose.

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 behaviour. 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.