Volume 19, Issue 6 (November 1991)
Analysis of Large Diameter High-Density Polyethylene Plastic Pipes As Vertical Shafts in Landfills
The recent trend in the increasing use of large diameter flexible plastic pipes as vertical shafts or manholes in landfills or hazardous waste containment areas has resulted in a need for a thorough understanding of the soil-structure interaction of these pipes for the purpose of design. In this paper the soil-structure interaction response of flexible vertical shafts in landfills is described. A plane strain finite element program is modified and converted into an axisymmetric finite element program which then is used to determine the displacements and stresses in the pipe and the surrounding fill. The analysis is comprehensive, considering the effects of incremental construction, compaction, and creep of the pipe and the fill material. The calculated responses of the finite element analysis are illustrated in a number of graphs which demonstrate how the lateral earth pressure, hoop stress and strain, vertical stress and strain, and vertical thrust in the pipe wall vary with the design variables. The variables are the pipe diameter and thickness, compaction level, duration of construction time, and fill depth. It is found that as the height of the pipe and fill increase, a stronger schedule of pipe needs to be used to prevent buckling. The hoop strain at the bottom of the pipe is the critical design element, since it is the only pipe response that increases with the soil and pipe creep.