Risk assessment of municipal solid waste (MSW) dumps using two-phase Random SPH: case study of three dumpsites

Rainfall and high leachate levels are the most prominent causes of MSW dumpsite instability. The multiphase mass flow originating from the failure of dumpsites often results in severe societal and environmental impacts. Numerical analysis and scenario simulation of the dumpsites from initiation to propagation is essential for strategizing risk mitigation. This study develops a two-phase Random SPH (RSPH) approach for modelling the large deformation MSW mass flows, incorporating spatial variability of material properties and pore-fluid pressure using the random field theory. The variability of MSW properties is characterized for uncertainty modelling based on the analysis of 584 laboratory tests on MSW from 28 countries. The proposed approach is applied for the risk assessment of three operational dumpsites, namely (i) Ghazipur dumpsite, Delhi, India, (ii) Koshe dumpsite, Addis Ababa, Ethiopia, and (iii) Hulene dumpsite, Maputo, Mozambique. Investigation of the uncontrolled and controlled surface infiltration scenarios indicated that providing a cover system over the waste dump is an effective risk minimization technique with a reduction of over 30% in the runout distance and over 40% in the maximum kinetic energy of the mass flow. Further, deterministic analysis with homogenous material properties is found to underestimate the vulnerability to failure, highlighting the significance of probabilistic approaches in identifying the high-risk zones around a dump site.