Jointed Pipeline Response To Large Ground Movements
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This thesis addresses the performance of jointed pipelines subject to ground deformations triggered at a large scale by earthquakes and a construction-related scale by tunneling. Understanding and quantifying jointed pipeline response at these scales allows for better design, operational management, and risk assessment of underground infrastructure, where cast iron (CI) and ductile iron (DI) pipelines in the U.S. account for approximately 75% of water distribution systems. The thesis covers the response of DI and molecularly oriented polyvinyl chloride (PVCO) pipelines to earthquaketriggered soil movement as well as CI and DI pipeline response to tunneling. A series of specially designed four-point bending experiments and 3D finite-element (FE) simulations were performed to characterize DI push-on joints commonly used in water distribution systems to develop a relationship between the rotation and axial pullout at both metal binding and first leakage. The results of uniaxial tension and onedimensional compression tests on the elastomeric gaskets in DI push-on joints were implemented in numerical models that show joint leakage to be independent of load path, with a unique pressure boundary that predicts leakage for many combinations of axial pullout and rotation. The increased circumferential strength, reduced pipe wall thickness, and enhanced cross-sectional flexibility of PVCO pipelines was evaluated through the characterization of PVCO material properties, axial joint tension and compression tests, four-point bending tests, and a full-scale fault rupture experiment. A nominal 150-mm (6-in.)diameter PVCO pipeline is able to accommodate significant fault movement through axial tensile and bending strains in the pipe in combination with modest levels of axial slip at the restrained joints. Relatively large levels of axial strain in the low modulus PVCO material, which varies between 1% and 2% at pipeline failure, are able to sustain substantial extension and compression from ground movements. Soil/pipeline interaction modeling was performed for vertical and horizontal ground movements caused by tunneling in jointed CI and DI pipelines perpendicular to the tunnel centerline that (1) extend beyond the width of the settlement profile and (2) connect through 90° tees with a pipeline parallel to the tunnel. The modeling incorporates the results of large-scale laboratory tests. Guidance is provided for design and the identification before tunneling of potential difficulties. In particular, CI tees are at high risk when subject to tunneling induced soil movement, whereas DI pipelines and tees have sufficient capacity to accommodate high levels of tunneling related ground deformation. iv
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Ingraffea,Anthony R