Response of a landfill drainage pipe buried in a trench

Abstract

The structural response of drainage pipes used in landfill leachate collection systems depends on the properties of both the pipe and the backfill soil, as well as the type of backfill configuration. The implications of using different backfill configurations for the structural performance of the pipe are discussed for laterally extensive blankets, mounds, and trenches. The objective of this paper is to quantify the structural performance of a landfill pipe when buried in a trench. Unlike in the trenches for many gravity-flow pipes, where only a proportion of the vertical overburden stresses may reach the pipe because of conventional trench arching, it is shown the stresses in a landfill trench may be larger than the overburden stresses. This occurs when the backfill in the trench is stiffer than the surrounding material, denoted as negative trench arching. Results from a large-scale laboratory test and numerical analysis of a pipe placed in a gravel trench cut into soft clay are presented. The configuration tested resulted in (a) negative trench arching that produced an increase in loads acting on the pipe; (b) softening of the gravel backfill surrounding the pipe, resulting in a decrease in pipe support; and (c) intrusion of clay into the voids between the gravel particles along the trench sidewall, causing a decrease in support to the pipe. All three of these factors resulted in increased pipe deflections.Key words: leachate collection pipe, landfill, polymer pipe, trench, arching.