Soil-pipe interaction studies leading to the laboratory observations of the effects ofdifferential ground movement between a heavy yielding structure and a pipeline firmly connected toit is presented in this paper. Such differential movements induce excessive stress concentrations onthe pipeline. Plastics pipes fail as a consequence of such movements, though their flexibility shouldmake them less vulnerable than rigid pipes. In order to evaluate the displacement, bending moment,shear force, vertical soil resistance at soil pipe interface under these conditions, innovativeexperimental techniques were developed and these are described in this paper. The soil resistance ona pipe section is characterised by the load-displacement behaviour of the embedded pipe sectionsubjected to lateral displacement, vertical displacement, axial displacement along the axis of thepipe and rotation about the pipe axis. A mathematical analysis to complement the laboratory studiesis developed and presented by treating the pipelines as a beam on elastic foundation. The magnitudeand location of the maximum bending moments arising from yielding of the heavy structure isexamined. The experimental observations of the behaviour of pipes subjected to such differentialground movement are compared with the results from the theoretical predictions. The provision ofrocker pipe joints that entertain a permitted rotation helps to redistribute the adverse bendingmoments to acceptable levels and thereby alleviate distress in the pipeline. The paper gives resultsthat demonstrate theoretically and experimentally the appropriateness of the use of flexibly jointedrocker pipes to prevent such failures. Field examples of the adoption of such joints is also presentedand discussed culminating with the expression of the need for rational design procedures forpipeline foundations including rocker pipes to be incorporated into codes of practice such as EN1295 is emphasised.
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