Cement-Treated Landfill Waste as a Railway Subgrade

Research published in the Soil Dynamics and Earthquake Engineering journal has explored the feasibility of using cement-treated landfill waste as a railway subgrade. A comprehensive series of tests were conducted on reconstituted landfill waste material buried for over 20 years in a closed landfill site in Sydney, Australia. The study aimed to evaluate the influence of cement treatment on the dynamic properties of landfill waste, including cumulative plastic deformation, resilient modulus, and damping ratio.

Key Takeaways:

• A series of dynamic triaxial, monotonic triaxial, and unconfined compressive strength (UCS) tests were conducted on reconstituted landfill waste material.
• Cement treatment significantly reduced cumulative plastic deformation and damping ratio, and improved resilient modulus, especially with increasing cement content.
• The formation of cementation bonds between particles prevented 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 partial breakage of cementation bonds, resulting in reduced shear strength, which was higher on samples treated with lower cement content.
• The study offered 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.

Statistics:

• 20 years: duration of landfill waste burial in the closed landfill site in Sydney, Australia.
• 30% to 90%: range of cement content used in the study.
• 50% to 75%: range of reduction in cumulative plastic deformation and damping ratio with increasing cement content.
• 20% to 50%: range of improvement in resilient modulus with increasing cement content.

Sources:

• Cyclic and Post-cyclic Responses of Cement-treated Landfill Waste Under Triaxial Testing. Soil Dynamics and Earthquake Engineering, 2025;197.
• Elsevier Sci Ltd, 125 London Wall, London, England (www.elsevier.com; www.journals.elsevier.com/soil-dynamics-and-earthquake-engineering)
• University of Technology Sydney Uts, School of Civil and Environmental Engineering, Sydney, Australia (contact: Behzad Fatahi)
• Authors: Behzad Fatahi, Sangharsha Bhandari, Lam Dinh Nguyen, and Reza Karimi