The structural performance of flexible pipe for landfill drainage

The structural performance of perforated plastic pipelines used for landfill drainage is difficult to predict. This paper aims to describe their structural action on the basis of field measurements, and thereby make recommendations for their design and installation. The key requirements for structural support of buried plastic pipes and development of stable arching are described for both embankment and trench conditions. The most important is the relative stiffness of the pipe surround, which is directly related to the degree of confinement. The ‘ground conditions’ in a landfill, however, are far removed from those of embankment fill, the variable nature of the waste resulting in a complex loading pattern and variable degrees of local confinement. Field measurements of pipes buried in different surround conditions in a landfill as the waste progressively increases in height are reported and compared with laboratory results. The deformed shape in the smaller gravel surrounds was found to differ from that in simulated laboratory tests, although classical theory was found to predict baseline pipe deformations reasonably well. Landfilling practice close to the gravel mounds was found to be critical to pipe performance.