A comprehensive series of tests, including dynamic triaxial, monotonic triaxial and unconfined compressive strength (UCS) tests, were carried out on reconstituted landfill waste material buried for over twenty years in a closed landfill site in Sydney, Australia. Waste materials collected from the landfill site were treated with varying percentages of cement, and both treated and untreated specimens were investigated to evaluate the influence of cement treatment. The study examined the dynamic properties of cement-treated landfill waste, including cumulative plastic deformation, resilient modulus, and damping ratio, and also analysed the impact of cyclic loading on post-cyclic shear strength in comparison to pre-cyclic shear strength. The UCS tests and monotonic triaxial tests demonstrated that untreated specimens subjected to monotonic loading exhibited a progressive increase in strength with rising axial strain, whereas cement-treated specimens reached a peak strength before experiencing a decline. During cyclic loading, with the inclusion of cement, a significant reduction in cumulative plastic deformation and damping ratio was observed, and this reduction was further enhanced with increasing cement content. Conversely, the resilient modulus showed substantial improvement with the addition of cement, and this enhancement was further amplified with increasing cement content. The formation of cementation bonds between particles curtails particle movement within the landfill waste material matrix and prevents interparticle sliding during cyclic loading, leading to lower plastic strains and damping ratio while increasing resilient modulus. Post-cyclic monotonic testing revealed that cyclic loading caused the partial breakage of the cementation bonds, resulting in reduced shear strength. This reduction was higher on samples treated with lower cement content. Overall, the findings of the research offer crucial insights into the possibility of cement-treated landfill waste as a railway subgrade, laying the groundwork for informed design decisions in developing transport infrastructure over closed landfill sites while using landfill waste materials available on site.

This study conducted a series of cyclic and monotonic triaxial tests on reconstituted landfill waste material from a closed landfill site in Sydney, Australia, to assess its dynamic behaviour under various testing conditions. Specifically, the effects of cyclic deviatoric stress, loading frequency, and effective confining stress on the cumulative plastic axial strain, resilient modulus, and damping ratio under undrained cyclic loading conditions were investigated. Results indicated that the plastic deformation, resilient modulus, and material damping are significantly influenced by dynamic stress and confining stress, with a lesser impact from loading frequency. Notably, as the number of loading cycles increased, the cumulative plastic axial strain and resilient modulus exhibited an increase, whereas the damping ratio decreased. Furthermore, increasing cyclic deviatoric stress led to an increase in both cumulative plastic axial strain and damping ratio, while an increase in confining stress resulted in a decrease in these parameters. Conversely, the resilient modulus showed an increase with rising cyclic deviatoric stress and confining stress. The influence of loading frequency on cumulative plastic axial strain and resilient modulus was minor, and its effect on the damping ratio was rather negligible. The study observed that initial loading cycles caused rearrangement and reorientation of waste components and the mobilisation of fibres with tensile forces as loading progressed, suggesting that these landfill waste samples behaved comparably to fibrous soil with randomly distributed fibres. Through nonlinear regression analysis, an empirical relationship for cumulative plastic axial strain incorporating cyclic deviatoric stress, confining stress, number of cycles, and frequency was derived. This research contributes valuable insights into the behaviour of compacted landfills as railway subgrades, providing a foundation for informed decision-making in the design of transport infrastructure over closed landfill sites.

Landfill mined soil-like fraction (LMSF) is the material obtained from mining of old waste. Utilization of LMSF in infrastructure applications is limited due to several challenges including possible presence of organic content, heavy metals, heterogeneous composition, etc., and require stabilization prior to usage. In light of this, LMSF was stabilized with alkali activated slag at different curing temperatures including freeze curing (- 21 degree celsius), ambient curing (25 degree celsius), thermal curing (60 degree celsius) and their combinations. Further, the performance of stabilized LMSF was evaluated on cyclic exposure to different climatic conditions, viz., - 21 degree celsius, 0 degree celsius, 10 degree celsius, 25 degree celsius and 45 degree celsius in both closed (without water exposure) and open system (water inundated) conditions. The performance of stabilized LMSF under these climatic conditions was evaluated through unconfined compressive strength (UCS), indirect tensile strength, cyclic loading tests, and microstructural aspects. Based on initial trials, ambient curing (25 degree celsius) and 2 days thermal curing at 60 degree celsius yielded better performance of stabilized LMSF. The 28 days stabilized LMSF has shown stable performance against cyclic exposure to different climatic conditions by satisfying the maximum allowable mass loss criteria after 12 cycles as per IRC-37, except for exposure to subfreezing temperature of - 21 degree celsius in open system. Further, not much reduction in UCS and indirect tensile (except for - 21 degree celsius in open system) strength was observed on cyclic exposure to different climatic conditions, inferring the stability of cementitious compounds and resistance against degradation. 2 days of thermal curing at 60 degrees C notably enhanced the performance of stabilized LMSF in different exposure conditions under both static and cyclic loading conditions, suggesting it as favourable curing condition for sustainable and low-cost stabilization of LMSF in different climatic conditions ranging from sub-freezing to arid regions.