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Permanent ground displacements (PGD) along or across pipeline alignments (e.g., landslides, surface fault rupture, and liquefaction) are the most significant seismic hazards for welded steel pipelines. A comprehensive summary of the methodology used to mitigate these hazards on major international oil and gas pipeline projects is presented along with a discussion of the ensuing implementation challenges. Key ingredients of pipeline geohazard mitigation include geohazard identification and characterization, assessment of rupture risk, pipeline/soil interaction analysis, strain-based design criteria, and weld strength and quality. The most significant problems arise from compressed schedules, which do not allow for the integration of this work. The paper begins with an overview of geohazards and their effects on pipelines with reference to industry rupture-rate statistics. It continues with a brief summary of geologic investigations, terrain evaluation, design criteria, design concepts, and engineering analysis techniques. Next, critical technical issues that often hamper progress and other problems typically encountered during project execution are identified. Suggestions for managing and coordinating geohazard mitigation within the context of preliminary and final project engineering phases of international projects are provided along with recommended approaches to avoid or lessen the impact of geohazard-related design and construction problems. The need for perceptive front-end planning is emphasized, especially as it relates to pipeline routing through potentially hazardous areas and interaction with regulators, government agencies, financiers, and other third-party organizations.Copyright © 2008 by ASME |
