Numerical Simulation Of Landfill Settlement On The Soft Ground

Settlement is an important concern in the management of municipal solid waste landfills. On the one hand, landfill capacity will increase if most of the settlement occurs during the initial or early filling stages. On the other hand, a large postclosure settlement is undesirable from a maintenance point of view, since it may lead to surface ponding, development of cracks in soil materials (such as compaceted clay lines), tearing of the geomembrane, and damage to the geocomposite drainage layer. In addition, ancillary landfill facilities, such as gas collection and drainage pipes and leachate injection pipes (as in bioreactor landfills), maybe damaged as a result of large differential postclosure settlement. In this dissertation, a series of research work, which is about waste settlement and landfill foundation settlement, is as follows:(1)Landfill settlement consists of waste settlement and landfill foundation settlement. In this thesis, settlement calculations from soil mechanics and finite element analyse are respectively calculated. What is more, I have compared and analysed the result of these two methods.(2)Make a numerical simulation of landfill settlement on the soft groud and draw the settlement-time curve of waste in the whole filling stage, calculate and analyse the shear and axial force of the compacted clay lines.(3)Apply the calculation result on Laogang MSW landfill of Shanghai, make an estimation on the influence of environment problems and the differential settlement.Through inducing and summarizing the rusults of settlement calculation, we have gotten some valuable conclusions as follows:(1)The calculation result from soil mechanics is little larger than the one from finite element analyse.(2)The factor of safety of the geomembrane against the mobilized tensile stresses of Laogang MSW landfill of Shanghai is 2.9, is safe for the liners system.(3)Assume that the HDPE geomembranes firmly anchored on the foundation slope, then the maximum prolongation rate of the HDPE geomembranes is 4.37%, sothe geomembranes is safe for the leachate and will not make pollution.(4)When the cover settles differentially, some part of it will be subjected to tension and will undergo tensile strain. Tensile strains are of concern because the larger the stretching (tensile strain), the greater the possibility that the soil will crack and that a geomembrane or geosynthetic clay liner will rupture.