Behavior of Bell and Spigot Joints in Buried Thermoplastic Pipelines

Failures in joints are among the most common sources of problems in buried gravity flow pipelines. Poor performance of these elements can cause infiltration and exfiltration, which lead to soil erosion and eventually to serviceability or strength limit states for the system. To prevent poor performance, joints should be designed to adequately accommodate the demands generated under normal loading conditions. Such demands are not clearly understood, however, because joint behavior has received scant attention. The goal of this research was to examine the response of gasketed bell and spigot joints in two, common, thermoplastic pipelines employed in gravity flow applications when subjected to live loading. The specimens examined were a high-density polyethylene pipeline, 1,500 mm in diameter, and a polyvinyl chloride (PVC) pipeline, 900 mm in diameter. Two burial depths and three loading locations were examined for each pipeline buried according to AASHTO guidelines. Moreover, two installations not specified by AASHTO were examined for the PVC specimen, which featured voids in the bedding under the joint. Subsequently, each specimen was loaded directly over the joint up to and beyond fully factored loads under recommended burial conditions to observe the joint performance and the final failure mode of the pipelines. The test measurements provide guidance on the key demands that develop at the joints and how they are influenced by the burial and loading condition. Finally, recommendations are made on the development of structural design procedures.