Behavior of branched buried MDPE gas distribution pipes under relative axial ground movements

Chakraborty, Sudipta (2022) Behavior of branched buried MDPE gas distribution pipes under relative axial ground movements. Masters thesis, Memorial University of Newfoundland.

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Abstract

The performance of medium density polyethylene (MDPE) gas distribution pipes subjected to relative ground movements has been a significant concern to the utility owners and companies. The tee-joints (tapping tee) and the lateral branches, common in gas distribution piping systems, may increase the effects of ground movement caused by various geohazards such as landslides, earthquakes etc. Most ground movement scenarios depict leak/stress concentration near the tapping tee of the branched pipe system. However, limited studies are currently available in the literature on the soil-pipe interaction of branched pipes during ground movement. Thus, the complex interactions of the pipe, the tee-junction, and the branch with surrounding soil are not well-understood. This thesis presents an experimental investigation of different configurations of 42.2-mm and 60.3-mm diameter branched buried MDPE pipes under relative axial ground movement. Tests with different positions of the tee-joint with respect to the pulling end of the pipe and varying densities of sand are conducted using the laboratory facility at Memorial University of Newfoundland. Pipe wall strains and soil pressures around the pipes are measured during the tests to capture the mechanism of soil-pipe interaction. Subsequently, an additional test is done with the tapping tee only (without the branch pipe) to identify the contribution of the branch pipe to soil resistance and pipe wall strain. The study explores the contribution of the trunk pipe, the tapping tee, and the branch pipe separately on the axial pulling force. Test results reveal the possibility of localized strain occurring on the trunk pipe near the tee. The anchoring effects of the tee and the branch significantly affect the soil resistance and the strain distribution on the trunk pipes.

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