A Model Based on Mechanics to Predict Settlements in Bioreactor Landfills

Prediction of waste settlement behavior during the construction phase of a landfill is vital to effective functioning of leachate recirculation systems and gas collection pipe network, yet prediction of waste settlement is complex and difficult to perform. Few models, are currently available which can be used to calculate landfill settlement of the entire waste thickness after closure without accounting for variation in density and other parameters with depth. By starting after closure, these models do not account for settlements during construction. The use of entire depth does not allow for the calculation of strains at different depths. When landfills are operated as bioreactors, waste decomposition and gas production are accelerated making the problem more complicated. Rapid degradation results in a significant impact on waste properties, settlement and stability. Accurate prediction of this rapid change in volume is of importance in estimating airspace, planning construction sequence, designing covers as well as planning for expansions. This paper focuses on the behavior of the density and settlements of waste with time and space and proposes a new mathematical model based on mechanics which is capable of computing settlements during construction of landfills. The impact of leachate recirculation and different waste types on settlement behavior of a landfill is also accounted in the proposed model