The structural interaction of pipe couplings used for trenchless construction.

Trenchless construction of underground services by the pipe jacking method has radically increased over the past thirty years, particularly in sensitive urban areas. Spoil is removed at the cutting face and the entire pipeline is pushed through an oversized tunnel bore by large hydraulic jacks. The pipeline inevitably deviates from the intended alignment due to site conditions and the skill level of the workforce. Poor directional control of the pipeline can lead to pipe joints opening which induces high stresses in the pipe and produces a loading mechanism for the structural element of the coupling system. This study has investigated the structural interaction of the pipe-packing-coupling system under installation conditions. A theoretical model for the lateral force exerted on the joint/coupling under misaligned conditions was proposed and verified by full scale laboratory experiments. The differential eccentricity of the resultant jacking force at joints abutting a misaligned joint determines the lateral force exerted on the deflected joint and hence coupling system. It is shown that long pipes are beneficial in this respect. This thesis considers the lateral force exerted on the joint under 'closed' and 'open' joint conditions. Such conditions occur due to minor deviations in the pipeline alignment with the open joint situation causing significant influence on the design of the coupling element. The Australian Concrete Pipe Association Linear Stress Approach (ACPALSA) for open joint analysis was modified to predict the interaction between the packing material and the pipe joint for chipboard packing material and clay pipes. This is of benefit for the prediction of lateral force acting at an open misaligned joint. A theoretical model for the prediction of principal tensile stresses induced in the structural element of the coupling was proposed and verified by full scale laboratory experiment. The design of the coupling should be based on points located at the centre of the coupling width due to edge effects associated with other locations. This point was shown to be critical in preliminary investigations and should be adopted for design purposes. The findings of this thesis are of interest to the pipe jacking industry as a whole through improved knowledge of the structural interaction at misaligned joints and through a scientific approach to the design of the coupling system. The pipe-coupling unit cost maybe properly managed through implementation of this thesis.