PREDICTIVE COMPUTER MODELING OF THE SURFACE SUBSIDENCE OF A SOLID WASTE STORAGE FACILITY AND GAS GENERATION UNDER UNSATURATED CONSOLIDATION CONDITIONS. RIVNE

The article considers the complex problem of organic residue biodegradation and landfill consolidation of municipal solid waste under unsaturated conditions.Particular attention is paid to the analysis of interconnected physico-chemical processes, including the biodegradation of organic components, moisture transfer, heat generation, and gas transport in a porous medium.A mathematical model has been developed that takes into account changes in the stress-strain state of the porous medium, heat and gas flows, and their interconnection with the processes of decomposition of organic residues.Modifications to the consolidation equations and kinematic boundary condition are made to model the dynamics of compaction with consideration of thermal and biodegradation factors.Numerical solutions of the corresponding one-dimensional nonlinear boundary value problem in the time-varying domain were found by the finite element method.The numerical experiments made it possible to study the influence of interrelated processes on the subsidence of the upper boundary of the repository, as well as on the volume of greenhouse gas generation.The results of the study showed that when taking into account the heat generation caused by the biodegradation of organic materials, temperatures in the lower layers of the repository can reach high values.This, in turn, leads to a decrease in the activity of microorganisms and, consequently, to a decrease in the intensity of gas generation and subsidence.It was found that neglecting the influence of temperature and humidity significantly changes the modeling results, in particular, reduces the level of temperatures, subsidence and overpressures in the gas component.The conducted numerical experiments confirmed the importance of accounting for interconnected processes to achieve accurate predictions of landfill conditions.This approach allows for more effective assessment of the impact of biodegradation processes on changes in the stress-strain state of the medium and supports informed decision-making regarding the operation of municipal solid waste landfills.