Three-dimensional settlement characteristics and accelerated stabilization of landfills under aerobic remediation

The settlement is an important index for evaluating the stabilization of a landfill. However, the settlement of an aerated landfill is extremely complex and highly coupled with waste biodegradation due to non-homogeneous distribution of oxygen. Thus, the traditional models for settlement of anaerobic landfills are not applicable to aerobic ones. A three-dimensional multi-field couped model for landfills is established considering anaerobic-aerobic biodegradation, liquid-gas migration, multi-component diffusion and elastic-plastic-degradation skeleton deformation. The finite volume method and the open source computing platform OpenFoam are used to solve the model, and the settlement and deformation characteristics of an aerobic landfill are revealed. The results show that the aeration can easily induce significant uneven settlement and relative displacement of waste-aeration well, e.g., reaching up to 0.7 m for a 10 m×10 m×15 m model in this paper, and the largest uneven settlement occurs at the intermediate stage of aeration. According to the China's national standard of highly utilizing landfills, the aerobic remediation can reduce the post-maintenance time of landfills by 88%, and a termination condition of 90% degradation degree is suggested for aerobic remediation of landfills to satisfy the criteria in terms of post-aeration settlement rate.