Current pipeline design practice within water, wastewater, and drainage pipe industries is largely based on the American Water Works Association (AWWA) design manuals and standards, American Society for Testing and Materials (ASTM) standards and American Association of State Highway and Transportation Officials (AASHTO) codes and design practices, respectively. AWWA, ASTM and AASHTO practices recognize the importance of proper specification and installation of bedding and backfill for achieving the intended structural performance of buried rigid and more importantly flexible pipelines. However, the guidance provided by various AWWA design manuals, specific for pipe materials, ASTM standards, and AASHTO codes use different terminology and requirements to classify and specify bedding and backfill materials based on the pipe material. This variability of bedding and backfill classification and specification requirements creates unnecessary confusion amongst pipeline designers and introduces a potential for unintended use of bedding and backfill materials. More importantly, the use of inconsistent and non-standard soil classification terminologies makes the interdisciplinary communications difficult, potentially resulting in inappropriate and inconsistent selection of engineering properties for the pipeline design.
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