Numerical Modeling of Dynamic Compaction Induced Settlement of MSW Landfills

Abstract

The objective of this study is to estimate dynamic compaction (DC) induced settlement of municipal solid waste (MSW) landfills using numerical modeling. Finite element (FE) based analysis is carried out and the corresponding reduction in waste volume, crater depth, and settlements induced at the ground surface due to densification are examined for a range of compression ratios of MSW. The response of MSW is modeled by adopting the Drucker-Prager constitutive law, and the effect of large strains developed during DC is simulated using the arbitrary Lagrangian-Eulerian (ALE) remeshing approach. The developed model is validated by comparing the numerical results with published settlement values from various landfill sites. The effectiveness of DC in increasing the design life and overall capacity of MSW landfills is subsequently investigated by varying waste compressibility, energy, momentum, and tamper radius. The analysis results indicated that the optimum number of tamper drops on MSW vary in the range 5–12 depending on waste compressibility, whereas, the optimum radius to be adopted in the field is approximately 1.6 m. In addition, the crater depth was found to increase for wastes with higher compressibility, and the effect of tamper momentum was found to be pronounced compared with tamper energy. Based on the optimized design parameters obtained, an empirical equation is formulated for predicting DC induced settlement of MSW landfills in the field. The utility of this study is to aid in decision making regarding the implementation of DC to MSW landfills and to focus the efforts of full-scale expensive field trials.